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Merge branches 'barrier.2012.05.09a', 'fixes.2012.04.26a', 'inline.2012.05.02b' and 'srcu.2012.05.07b' into HEAD 

barrier:  Reduce the amount of disturbance by rcu_barrier() to the rest of
    	the system.  This branch also includes improvements to
    	RCU_FAST_NO_HZ, which are included here due to conflicts.
fixes:  Miscellaneous fixes.
inline:  Remaining changes from an abortive attempt to inline
    	preemptible RCU's __rcu_read_lock().  These are (1) making
    	exit_rcu() avoid unnecessary work and (2) avoiding having
    	preemptible RCU record a blocked thread when the scheduler
    	declines to do a context switch.
srcu:	Lai Jiangshan's algorithmic implementation of SRCU, including
    	call_srcu().
This commit is contained in:
Paul E. McKenney 2012-05-11 10:14:09 -07:00
Родитель b1420f1c8b 048a0e8f5e 9dd8fb16c3 9fab97876a
Коммит dc36be4419
21 изменённых файлов: 1035 добавлений и 237 удалений
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15
Documentation/RCU/torture.txt
Просмотреть файл

@ -47,6 +47,16 @@ irqreader Says to invoke RCU readers from irq level. This is currently
permit this. (Or, more accurately, variants of RCU that do
-not- permit this know to ignore this variable.)
n_barrier_cbs If this is nonzero, RCU barrier testing will be conducted,
in which case n_barrier_cbs specifies the number of
RCU callbacks (and corresponding kthreads) to use for
this testing. The value cannot be negative. If you
specify this to be non-zero when torture_type indicates a
synchronous RCU implementation (one for which a member of
the synchronize_rcu() rather than the call_rcu() family is
used -- see the documentation for torture_type below), an
error will be reported and no testing will be carried out.
nfakewriters This is the number of RCU fake writer threads to run. Fake
writer threads repeatedly use the synchronous "wait for
current readers" function of the interface selected by
@ -188,7 +198,7 @@ OUTPUT
The statistics output is as follows:
rcu-torture:--- Start of test: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
rcu-torture: rtc: (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
rcu-torture: rtc: (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
rcu-torture: Reader Pipe: 727860534 34213 0 0 0 0 0 0 0 0 0
rcu-torture: Reader Batch: 727877838 17003 0 0 0 0 0 0 0 0 0
rcu-torture: Free-Block Circulation: 155440 155440 155440 155440 155440 155440 155440 155440 155440 155440 0
@ -230,6 +240,9 @@ o "rtmbe": A non-zero value indicates that rcutorture believes that
rcu_assign_pointer() and rcu_dereference() are not working
correctly. This value should be zero.
o "rtbe": A non-zero value indicates that one of the rcu_barrier()
family of functions is not working correctly.
o "rtbke": rcutorture was unable to create the real-time kthreads
used to force RCU priority inversion. This value should be zero.

88
Documentation/kernel-parameters.txt
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@ -2330,18 +2330,100 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
See Documentation/blockdev/ramdisk.txt.
rcupdate.blimit= [KNL,BOOT]
rcutree.blimit= [KNL,BOOT]
Set maximum number of finished RCU callbacks to process
in one batch.
rcupdate.qhimark= [KNL,BOOT]
rcutree.qhimark= [KNL,BOOT]
Set threshold of queued
RCU callbacks over which batch limiting is disabled.
rcupdate.qlowmark= [KNL,BOOT]
rcutree.qlowmark= [KNL,BOOT]
Set threshold of queued RCU callbacks below which
batch limiting is re-enabled.
rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
Suppress RCU CPU stall warning messages.
rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
Set timeout for RCU CPU stall warning messages.
rcutorture.fqs_duration= [KNL,BOOT]
Set duration of force_quiescent_state bursts.
rcutorture.fqs_holdoff= [KNL,BOOT]
Set holdoff time within force_quiescent_state bursts.
rcutorture.fqs_stutter= [KNL,BOOT]
Set wait time between force_quiescent_state bursts.
rcutorture.irqreader= [KNL,BOOT]
Test RCU readers from irq handlers.
rcutorture.n_barrier_cbs= [KNL,BOOT]
Set callbacks/threads for rcu_barrier() testing.
rcutorture.nfakewriters= [KNL,BOOT]
Set number of concurrent RCU writers. These just
stress RCU, they don't participate in the actual
test, hence the "fake".
rcutorture.nreaders= [KNL,BOOT]
Set number of RCU readers.
rcutorture.onoff_holdoff= [KNL,BOOT]
Set time (s) after boot for CPU-hotplug testing.
rcutorture.onoff_interval= [KNL,BOOT]
Set time (s) between CPU-hotplug operations, or
zero to disable CPU-hotplug testing.
rcutorture.shuffle_interval= [KNL,BOOT]
Set task-shuffle interval (s). Shuffling tasks
allows some CPUs to go into dyntick-idle mode
during the rcutorture test.
rcutorture.shutdown_secs= [KNL,BOOT]
Set time (s) after boot system shutdown. This
is useful for hands-off automated testing.
rcutorture.stall_cpu= [KNL,BOOT]
Duration of CPU stall (s) to test RCU CPU stall
warnings, zero to disable.
rcutorture.stall_cpu_holdoff= [KNL,BOOT]
Time to wait (s) after boot before inducing stall.
rcutorture.stat_interval= [KNL,BOOT]
Time (s) between statistics printk()s.
rcutorture.stutter= [KNL,BOOT]
Time (s) to stutter testing, for example, specifying
five seconds causes the test to run for five seconds,
wait for five seconds, and so on. This tests RCU's
ability to transition abruptly to and from idle.
rcutorture.test_boost= [KNL,BOOT]
Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
"Maybe" means test if the RCU implementation
under test support RCU priority boosting.
rcutorture.test_boost_duration= [KNL,BOOT]
Duration (s) of each individual boost test.
rcutorture.test_boost_interval= [KNL,BOOT]
Interval (s) between each boost test.
rcutorture.test_no_idle_hz= [KNL,BOOT]
Test RCU's dyntick-idle handling. See also the
rcutorture.shuffle_interval parameter.
rcutorture.torture_type= [KNL,BOOT]
Specify the RCU implementation to test.
rcutorture.verbose= [KNL,BOOT]
Enable additional printk() statements.
rdinit= [KNL]
Format: <full_path>
Run specified binary instead of /init from the ramdisk,

14
MAINTAINERS
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@ -5607,14 +5607,13 @@ F: net/rds/
READ-COPY UPDATE (RCU)
M: Dipankar Sarma <dipankar@in.ibm.com>
M: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
W: http://www.rdrop.com/users/paulmck/rclock/
W: http://www.rdrop.com/users/paulmck/RCU/
S: Supported
T: git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
F: Documentation/RCU/
X: Documentation/RCU/torture.txt
F: include/linux/rcu*
F: include/linux/srcu*
F: kernel/rcu*
F: kernel/srcu*
X: kernel/rcutorture.c
REAL TIME CLOCK (RTC) SUBSYSTEM
@ -6131,6 +6130,15 @@ S: Maintained
F: include/linux/sl?b*.h
F: mm/sl?b.c
SLEEPABLE READ-COPY UPDATE (SRCU)
M: Lai Jiangshan <laijs@cn.fujitsu.com>
M: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
W: http://www.rdrop.com/users/paulmck/RCU/
S: Supported
T: git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
F: include/linux/srcu*
F: kernel/srcu*
SMC91x ETHERNET DRIVER
M: Nicolas Pitre <nico@fluxnic.net>
S: Odd Fixes

1
arch/um/drivers/mconsole_kern.c
Просмотреть файл

@ -705,6 +705,7 @@ static void stack_proc(void *arg)
struct task_struct *from = current, *to = arg;
to->thread.saved_task = from;
rcu_switch_from(from);
switch_to(from, to, from);
}

40
include/linux/rculist.h
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@ -30,6 +30,7 @@
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
#ifndef CONFIG_DEBUG_LIST
static inline void __list_add_rcu(struct list_head *new,
struct list_head *prev, struct list_head *next)
{
@ -38,6 +39,10 @@ static inline void __list_add_rcu(struct list_head *new,
rcu_assign_pointer(list_next_rcu(prev), new);
next->prev = new;
}
#else
extern void __list_add_rcu(struct list_head *new,
struct list_head *prev, struct list_head *next);
#endif
/**
* list_add_rcu - add a new entry to rcu-protected list
@ -108,7 +113,7 @@ static inline void list_add_tail_rcu(struct list_head *new,
*/
static inline void list_del_rcu(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
__list_del_entry(entry);
entry->prev = LIST_POISON2;
}
@ -228,18 +233,43 @@ static inline void list_splice_init_rcu(struct list_head *list,
})
/**
* list_first_entry_rcu - get the first element from a list
* Where are list_empty_rcu() and list_first_entry_rcu()?
*
* Implementing those functions following their counterparts list_empty() and
* list_first_entry() is not advisable because they lead to subtle race
* conditions as the following snippet shows:
*
* if (!list_empty_rcu(mylist)) {
* struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member);
* do_something(bar);
* }
*
* The list may not be empty when list_empty_rcu checks it, but it may be when
* list_first_entry_rcu rereads the ->next pointer.
*
* Rereading the ->next pointer is not a problem for list_empty() and
* list_first_entry() because they would be protected by a lock that blocks
* writers.
*
* See list_first_or_null_rcu for an alternative.
*/
/**
* list_first_or_null_rcu - get the first element from a list
* @ptr: the list head to take the element from.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*
* Note, that list is expected to be not empty.
* Note that if the list is empty, it returns NULL.
*
* This primitive may safely run concurrently with the _rcu list-mutation
* primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
*/
#define list_first_entry_rcu(ptr, type, member) \
list_entry_rcu((ptr)->next, type, member)
#define list_first_or_null_rcu(ptr, type, member) \
({struct list_head *__ptr = (ptr); \
struct list_head __rcu *__next = list_next_rcu(__ptr); \
likely(__ptr != __next) ? container_of(__next, type, member) : NULL; \
})
/**
* list_for_each_entry_rcu - iterate over rcu list of given type

20
include/linux/rcupdate.h
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@ -184,12 +184,14 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern void rcu_preempt_note_context_switch(void);
extern void rcu_check_callbacks(int cpu, int user);
struct notifier_block;
extern void rcu_idle_enter(void);
extern void rcu_idle_exit(void);
extern void rcu_irq_enter(void);
extern void rcu_irq_exit(void);
extern void exit_rcu(void);
/**
* RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
@ -922,6 +924,21 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset)
kfree_call_rcu(head, (rcu_callback)offset);
}
/*
* Does the specified offset indicate that the corresponding rcu_head
* structure can be handled by kfree_rcu()?
*/
#define __is_kfree_rcu_offset(offset) ((offset) < 4096)
/*
* Helper macro for kfree_rcu() to prevent argument-expansion eyestrain.
*/
#define __kfree_rcu(head, offset) \
do { \
BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \
call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \
} while (0)
/**
* kfree_rcu() - kfree an object after a grace period.
* @ptr: pointer to kfree
@ -944,6 +961,9 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset)
*
* Note that the allowable offset might decrease in the future, for example,
* to allow something like kmem_cache_free_rcu().
*
* The BUILD_BUG_ON check must not involve any function calls, hence the
* checks are done in macros here.
*/
#define kfree_rcu(ptr, rcu_head) \
__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))

11
include/linux/rcutiny.h
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@ -87,14 +87,6 @@ static inline void kfree_call_rcu(struct rcu_head *head,
#ifdef CONFIG_TINY_RCU
static inline void rcu_preempt_note_context_switch(void)
{
}
static inline void exit_rcu(void)
{
}
static inline int rcu_needs_cpu(int cpu)
{
return 0;
@ -102,8 +94,6 @@ static inline int rcu_needs_cpu(int cpu)
#else /* #ifdef CONFIG_TINY_RCU */
void rcu_preempt_note_context_switch(void);
extern void exit_rcu(void);
int rcu_preempt_needs_cpu(void);
static inline int rcu_needs_cpu(int cpu)
@ -116,7 +106,6 @@ static inline int rcu_needs_cpu(int cpu)
static inline void rcu_note_context_switch(int cpu)
{
rcu_sched_qs(cpu);
rcu_preempt_note_context_switch();
}
/*

19
include/linux/rcutree.h
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@ -45,18 +45,6 @@ static inline void rcu_virt_note_context_switch(int cpu)
rcu_note_context_switch(cpu);
}
#ifdef CONFIG_TREE_PREEMPT_RCU
extern void exit_rcu(void);
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
static inline void exit_rcu(void)
{
}
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
extern void synchronize_rcu_bh(void);
extern void synchronize_sched_expedited(void);
extern void synchronize_rcu_expedited(void);
@ -98,13 +86,6 @@ extern void rcu_force_quiescent_state(void);
extern void rcu_bh_force_quiescent_state(void);
extern void rcu_sched_force_quiescent_state(void);
/* A context switch is a grace period for RCU-sched and RCU-bh. */
static inline int rcu_blocking_is_gp(void)
{
might_sleep(); /* Check for RCU read-side critical section. */
return num_online_cpus() == 1;
}
extern void rcu_scheduler_starting(void);
extern int rcu_scheduler_active __read_mostly;

10
include/linux/sched.h
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@ -1905,12 +1905,22 @@ static inline void rcu_copy_process(struct task_struct *p)
INIT_LIST_HEAD(&p->rcu_node_entry);
}
static inline void rcu_switch_from(struct task_struct *prev)
{
if (prev->rcu_read_lock_nesting != 0)
rcu_preempt_note_context_switch();
}
#else
static inline void rcu_copy_process(struct task_struct *p)
{
}
static inline void rcu_switch_from(struct task_struct *prev)
{
}
#endif
#ifdef CONFIG_SMP

48
include/linux/srcu.h
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@ -29,26 +29,35 @@
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
struct srcu_struct_array {
int c[2];
unsigned long c[2];
unsigned long seq[2];
};
struct rcu_batch {
struct rcu_head *head, **tail;
};
struct srcu_struct {
int completed;
unsigned completed;
struct srcu_struct_array __percpu *per_cpu_ref;
struct mutex mutex;
spinlock_t queue_lock; /* protect ->batch_queue, ->running */
bool running;
/* callbacks just queued */
struct rcu_batch batch_queue;
/* callbacks try to do the first check_zero */
struct rcu_batch batch_check0;
/* callbacks done with the first check_zero and the flip */
struct rcu_batch batch_check1;
struct rcu_batch batch_done;
struct delayed_work work;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
};
#ifndef CONFIG_PREEMPT
#define srcu_barrier() barrier()
#else /* #ifndef CONFIG_PREEMPT */
#define srcu_barrier()
#endif /* #else #ifndef CONFIG_PREEMPT */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
int __init_srcu_struct(struct srcu_struct *sp, const char *name,
@ -67,12 +76,33 @@ int init_srcu_struct(struct srcu_struct *sp);
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
/**
* call_srcu() - Queue a callback for invocation after an SRCU grace period
* @sp: srcu_struct in queue the callback
* @head: structure to be used for queueing the SRCU callback.
* @func: function to be invoked after the SRCU grace period
*
* The callback function will be invoked some time after a full SRCU
* grace period elapses, in other words after all pre-existing SRCU
* read-side critical sections have completed. However, the callback
* function might well execute concurrently with other SRCU read-side
* critical sections that started after call_srcu() was invoked. SRCU
* read-side critical sections are delimited by srcu_read_lock() and
* srcu_read_unlock(), and may be nested.
*
* The callback will be invoked from process context, but must nevertheless
* be fast and must not block.
*/
void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
void (*func)(struct rcu_head *head));
void cleanup_srcu_struct(struct srcu_struct *sp);
int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
void synchronize_srcu(struct srcu_struct *sp);
void synchronize_srcu_expedited(struct srcu_struct *sp);
long srcu_batches_completed(struct srcu_struct *sp);
void srcu_barrier(struct srcu_struct *sp);
#ifdef CONFIG_DEBUG_LOCK_ALLOC

50
init/Kconfig
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@ -458,6 +458,33 @@ config RCU_FANOUT
Select a specific number if testing RCU itself.
Take the default if unsure.
config RCU_FANOUT_LEAF
int "Tree-based hierarchical RCU leaf-level fanout value"
range 2 RCU_FANOUT if 64BIT
range 2 RCU_FANOUT if !64BIT
depends on TREE_RCU || TREE_PREEMPT_RCU
default 16
help
This option controls the leaf-level fanout of hierarchical
implementations of RCU, and allows trading off cache misses
against lock contention. Systems that synchronize their
scheduling-clock interrupts for energy-efficiency reasons will
want the default because the smaller leaf-level fanout keeps
lock contention levels acceptably low. Very large systems
(hundreds or thousands of CPUs) will instead want to set this
value to the maximum value possible in order to reduce the
number of cache misses incurred during RCU's grace-period
initialization. These systems tend to run CPU-bound, and thus
are not helped by synchronized interrupts, and thus tend to
skew them, which reduces lock contention enough that large
leaf-level fanouts work well.
Select a specific number if testing RCU itself.
Select the maximum permissible value for large systems.
Take the default if unsure.
config RCU_FANOUT_EXACT
bool "Disable tree-based hierarchical RCU auto-balancing"
depends on TREE_RCU || TREE_PREEMPT_RCU
@ -515,10 +542,25 @@ config RCU_BOOST_PRIO
depends on RCU_BOOST
default 1
help
This option specifies the real-time priority to which preempted
RCU readers are to be boosted. If you are working with CPU-bound
real-time applications, you should specify a priority higher then
the highest-priority CPU-bound application.
This option specifies the real-time priority to which long-term
preempted RCU readers are to be boosted. If you are working
with a real-time application that has one or more CPU-bound
threads running at a real-time priority level, you should set
RCU_BOOST_PRIO to a priority higher then the highest-priority
real-time CPU-bound thread. The default RCU_BOOST_PRIO value
of 1 is appropriate in the common case, which is real-time
applications that do not have any CPU-bound threads.
Some real-time applications might not have a single real-time
thread that saturates a given CPU, but instead might have
multiple real-time threads that, taken together, fully utilize
that CPU. In this case, you should set RCU_BOOST_PRIO to
a priority higher than the lowest-priority thread that is
conspiring to prevent the CPU from running any non-real-time
tasks. For example, if one thread at priority 10 and another
thread at priority 5 are between themselves fully consuming
the CPU time on a given CPU, then RCU_BOOST_PRIO should be
set to priority 6 or higher.
Specify the real-time priority, or take the default if unsure.

28
kernel/rcupdate.c
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@ -51,6 +51,34 @@
#include "rcu.h"
#ifdef CONFIG_PREEMPT_RCU
/*
* Check for a task exiting while in a preemptible-RCU read-side
* critical section, clean up if so. No need to issue warnings,
* as debug_check_no_locks_held() already does this if lockdep
* is enabled.
*/
void exit_rcu(void)
{
struct task_struct *t = current;
if (likely(list_empty(&current->rcu_node_entry)))
return;
t->rcu_read_lock_nesting = 1;
barrier();
t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
__rcu_read_unlock();
}
#else /* #ifdef CONFIG_PREEMPT_RCU */
void exit_rcu(void)
{
}
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
struct lockdep_map rcu_lock_map =

16
kernel/rcutiny_plugin.h
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@ -851,22 +851,6 @@ int rcu_preempt_needs_cpu(void)
return rcu_preempt_ctrlblk.rcb.rcucblist != NULL;
}
/*
* Check for a task exiting while in a preemptible -RCU read-side
* critical section, clean up if so. No need to issue warnings,
* as debug_check_no_locks_held() already does this if lockdep
* is enabled.
*/
void exit_rcu(void)
{
struct task_struct *t = current;
if (t->rcu_read_lock_nesting == 0)
return;
t->rcu_read_lock_nesting = 1;
__rcu_read_unlock();
}
#else /* #ifdef CONFIG_TINY_PREEMPT_RCU */
#ifdef CONFIG_RCU_TRACE

257
kernel/rcutorture.c
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@ -64,6 +64,7 @@ static int irqreader = 1; /* RCU readers from irq (timers). */
static int fqs_duration; /* Duration of bursts (us), 0 to disable. */
static int fqs_holdoff; /* Hold time within burst (us). */
static int fqs_stutter = 3; /* Wait time between bursts (s). */
static int n_barrier_cbs; /* Number of callbacks to test RCU barriers. */
static int onoff_interval; /* Wait time between CPU hotplugs, 0=disable. */
static int onoff_holdoff; /* Seconds after boot before CPU hotplugs. */
static int shutdown_secs; /* Shutdown time (s). <=0 for no shutdown. */
@ -96,6 +97,8 @@ module_param(fqs_holdoff, int, 0444);
MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)");
module_param(fqs_stutter, int, 0444);
MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
module_param(n_barrier_cbs, int, 0444);
MODULE_PARM_DESC(n_barrier_cbs, "# of callbacks/kthreads for barrier testing");
module_param(onoff_interval, int, 0444);
MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
module_param(onoff_holdoff, int, 0444);
@ -139,6 +142,8 @@ static struct task_struct *shutdown_task;
static struct task_struct *onoff_task;
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static struct task_struct *stall_task;
static struct task_struct **barrier_cbs_tasks;
static struct task_struct *barrier_task;
#define RCU_TORTURE_PIPE_LEN 10
@ -164,6 +169,7 @@ static atomic_t n_rcu_torture_alloc_fail;
static atomic_t n_rcu_torture_free;
static atomic_t n_rcu_torture_mberror;
static atomic_t n_rcu_torture_error;
static long n_rcu_torture_barrier_error;
static long n_rcu_torture_boost_ktrerror;
static long n_rcu_torture_boost_rterror;
static long n_rcu_torture_boost_failure;
@ -173,6 +179,8 @@ static long n_offline_attempts;
static long n_offline_successes;
static long n_online_attempts;
static long n_online_successes;
static long n_barrier_attempts;
static long n_barrier_successes;
static struct list_head rcu_torture_removed;
static cpumask_var_t shuffle_tmp_mask;
@ -197,6 +205,10 @@ static unsigned long shutdown_time; /* jiffies to system shutdown. */
static unsigned long boost_starttime; /* jiffies of next boost test start. */
DEFINE_MUTEX(boost_mutex); /* protect setting boost_starttime */
/* and boost task create/destroy. */
static atomic_t barrier_cbs_count; /* Barrier callbacks registered. */
static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */
static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
/* Mediate rmmod and system shutdown. Concurrent rmmod & shutdown illegal! */
@ -327,6 +339,7 @@ struct rcu_torture_ops {
int (*completed)(void);
void (*deferred_free)(struct rcu_torture *p);
void (*sync)(void);
void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
void (*cb_barrier)(void);
void (*fqs)(void);
int (*stats)(char *page);
@ -417,6 +430,7 @@ static struct rcu_torture_ops rcu_ops = {
.completed = rcu_torture_completed,
.deferred_free = rcu_torture_deferred_free,
.sync = synchronize_rcu,
.call = call_rcu,
.cb_barrier = rcu_barrier,
.fqs = rcu_force_quiescent_state,
.stats = NULL,
@ -460,6 +474,7 @@ static struct rcu_torture_ops rcu_sync_ops = {
.completed = rcu_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = synchronize_rcu,
.call = NULL,
.cb_barrier = NULL,
.fqs = rcu_force_quiescent_state,
.stats = NULL,
@ -477,6 +492,7 @@ static struct rcu_torture_ops rcu_expedited_ops = {
.completed = rcu_no_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = synchronize_rcu_expedited,
.call = NULL,
.cb_barrier = NULL,
.fqs = rcu_force_quiescent_state,
.stats = NULL,
@ -519,6 +535,7 @@ static struct rcu_torture_ops rcu_bh_ops = {
.completed = rcu_bh_torture_completed,
.deferred_free = rcu_bh_torture_deferred_free,
.sync = synchronize_rcu_bh,
.call = call_rcu_bh,
.cb_barrier = rcu_barrier_bh,
.fqs = rcu_bh_force_quiescent_state,
.stats = NULL,
@ -535,6 +552,7 @@ static struct rcu_torture_ops rcu_bh_sync_ops = {
.completed = rcu_bh_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = synchronize_rcu_bh,
.call = NULL,
.cb_barrier = NULL,
.fqs = rcu_bh_force_quiescent_state,
.stats = NULL,
@ -551,6 +569,7 @@ static struct rcu_torture_ops rcu_bh_expedited_ops = {
.completed = rcu_bh_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = synchronize_rcu_bh_expedited,
.call = NULL,
.cb_barrier = NULL,
.fqs = rcu_bh_force_quiescent_state,
.stats = NULL,
@ -606,6 +625,11 @@ static int srcu_torture_completed(void)
return srcu_batches_completed(&srcu_ctl);
}
static void srcu_torture_deferred_free(struct rcu_torture *rp)
{
call_srcu(&srcu_ctl, &rp->rtort_rcu, rcu_torture_cb);
}
static void srcu_torture_synchronize(void)
{
synchronize_srcu(&srcu_ctl);
@ -620,7 +644,7 @@ static int srcu_torture_stats(char *page)
cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
torture_type, TORTURE_FLAG, idx);
for_each_possible_cpu(cpu) {
cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
cnt += sprintf(&page[cnt], " %d(%lu,%lu)", cpu,
per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
}
@ -635,13 +659,29 @@ static struct rcu_torture_ops srcu_ops = {
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock,
.completed = srcu_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.deferred_free = srcu_torture_deferred_free,
.sync = srcu_torture_synchronize,
.call = NULL,
.cb_barrier = NULL,
.stats = srcu_torture_stats,
.name = "srcu"
};
static struct rcu_torture_ops srcu_sync_ops = {
.init = srcu_torture_init,
.cleanup = srcu_torture_cleanup,
.readlock = srcu_torture_read_lock,
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock,
.completed = srcu_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = srcu_torture_synchronize,
.call = NULL,
.cb_barrier = NULL,
.stats = srcu_torture_stats,
.name = "srcu_sync"
};
static int srcu_torture_read_lock_raw(void) __acquires(&srcu_ctl)
{
return srcu_read_lock_raw(&srcu_ctl);
@ -659,13 +699,29 @@ static struct rcu_torture_ops srcu_raw_ops = {
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock_raw,
.completed = srcu_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.deferred_free = srcu_torture_deferred_free,
.sync = srcu_torture_synchronize,
.call = NULL,
.cb_barrier = NULL,
.stats = srcu_torture_stats,
.name = "srcu_raw"
};
static struct rcu_torture_ops srcu_raw_sync_ops = {
.init = srcu_torture_init,
.cleanup = srcu_torture_cleanup,
.readlock = srcu_torture_read_lock_raw,
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock_raw,
.completed = srcu_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = srcu_torture_synchronize,
.call = NULL,
.cb_barrier = NULL,
.stats = srcu_torture_stats,
.name = "srcu_raw_sync"
};
static void srcu_torture_synchronize_expedited(void)
{
synchronize_srcu_expedited(&srcu_ctl);
@ -680,6 +736,7 @@ static struct rcu_torture_ops srcu_expedited_ops = {
.completed = srcu_torture_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = srcu_torture_synchronize_expedited,
.call = NULL,
.cb_barrier = NULL,
.stats = srcu_torture_stats,
.name = "srcu_expedited"
@ -1129,7 +1186,8 @@ rcu_torture_printk(char *page)
"rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d "
"rtmbe: %d rtbke: %ld rtbre: %ld "
"rtbf: %ld rtb: %ld nt: %ld "
"onoff: %ld/%ld:%ld/%ld",
"onoff: %ld/%ld:%ld/%ld "
"barrier: %ld/%ld:%ld",
rcu_torture_current,
rcu_torture_current_version,
list_empty(&rcu_torture_freelist),
@ -1145,14 +1203,17 @@ rcu_torture_printk(char *page)
n_online_successes,
n_online_attempts,
n_offline_successes,
n_offline_attempts);
n_offline_attempts,
n_barrier_successes,
n_barrier_attempts,
n_rcu_torture_barrier_error);
cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
if (atomic_read(&n_rcu_torture_mberror) != 0 ||
n_rcu_torture_barrier_error != 0 ||
n_rcu_torture_boost_ktrerror != 0 ||
n_rcu_torture_boost_rterror != 0 ||
n_rcu_torture_boost_failure != 0)
cnt += sprintf(&page[cnt], " !!!");
cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
if (i > 1) {
n_rcu_torture_boost_failure != 0 ||
i > 1) {
cnt += sprintf(&page[cnt], "!!! ");
atomic_inc(&n_rcu_torture_error);
WARN_ON_ONCE(1);
@ -1337,6 +1398,7 @@ static void rcutorture_booster_cleanup(int cpu)
/* This must be outside of the mutex, otherwise deadlock! */
kthread_stop(t);
boost_tasks[cpu] = NULL;
}
static int rcutorture_booster_init(int cpu)
@ -1484,13 +1546,15 @@ static void rcu_torture_onoff_cleanup(void)
return;
VERBOSE_PRINTK_STRING("Stopping rcu_torture_onoff task");
kthread_stop(onoff_task);
onoff_task = NULL;
}
#else /* #ifdef CONFIG_HOTPLUG_CPU */
static void
static int
rcu_torture_onoff_init(void)
{
return 0;
}
static void rcu_torture_onoff_cleanup(void)
@ -1554,6 +1618,152 @@ static void rcu_torture_stall_cleanup(void)
return;
VERBOSE_PRINTK_STRING("Stopping rcu_torture_stall_task.");
kthread_stop(stall_task);
stall_task = NULL;
}
/* Callback function for RCU barrier testing. */
void rcu_torture_barrier_cbf(struct rcu_head *rcu)
{
atomic_inc(&barrier_cbs_invoked);
}
/* kthread function to register callbacks used to test RCU barriers. */
static int rcu_torture_barrier_cbs(void *arg)
{
long myid = (long)arg;
struct rcu_head rcu;
init_rcu_head_on_stack(&rcu);
VERBOSE_PRINTK_STRING("rcu_torture_barrier_cbs task started");
set_user_nice(current, 19);
do {
wait_event(barrier_cbs_wq[myid],
atomic_read(&barrier_cbs_count) == n_barrier_cbs ||
kthread_should_stop() ||
fullstop != FULLSTOP_DONTSTOP);
if (kthread_should_stop() || fullstop != FULLSTOP_DONTSTOP)
break;
cur_ops->call(&rcu, rcu_torture_barrier_cbf);
if (atomic_dec_and_test(&barrier_cbs_count))
wake_up(&barrier_wq);
} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
VERBOSE_PRINTK_STRING("rcu_torture_barrier_cbs task stopping");
rcutorture_shutdown_absorb("rcu_torture_barrier_cbs");
while (!kthread_should_stop())
schedule_timeout_interruptible(1);
cur_ops->cb_barrier();
destroy_rcu_head_on_stack(&rcu);
return 0;
}
/* kthread function to drive and coordinate RCU barrier testing. */
static int rcu_torture_barrier(void *arg)
{
int i;
VERBOSE_PRINTK_STRING("rcu_torture_barrier task starting");
do {
atomic_set(&barrier_cbs_invoked, 0);
atomic_set(&barrier_cbs_count, n_barrier_cbs);
/* wake_up() path contains the required barriers. */
for (i = 0; i < n_barrier_cbs; i++)
wake_up(&barrier_cbs_wq[i]);
wait_event(barrier_wq,
atomic_read(&barrier_cbs_count) == 0 ||
kthread_should_stop() ||
fullstop != FULLSTOP_DONTSTOP);
if (kthread_should_stop() || fullstop != FULLSTOP_DONTSTOP)
break;
n_barrier_attempts++;
cur_ops->cb_barrier();
if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
n_rcu_torture_barrier_error++;
WARN_ON_ONCE(1);
}
n_barrier_successes++;
schedule_timeout_interruptible(HZ / 10);
} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
VERBOSE_PRINTK_STRING("rcu_torture_barrier task stopping");
rcutorture_shutdown_absorb("rcu_torture_barrier_cbs");
while (!kthread_should_stop())
schedule_timeout_interruptible(1);
return 0;
}
/* Initialize RCU barrier testing. */
static int rcu_torture_barrier_init(void)
{
int i;
int ret;
if (n_barrier_cbs == 0)
return 0;
if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
printk(KERN_ALERT "%s" TORTURE_FLAG
" Call or barrier ops missing for %s,\n",
torture_type, cur_ops->name);
printk(KERN_ALERT "%s" TORTURE_FLAG
" RCU barrier testing omitted from run.\n",
torture_type);
return 0;
}
atomic_set(&barrier_cbs_count, 0);
atomic_set(&barrier_cbs_invoked, 0);
barrier_cbs_tasks =
kzalloc(n_barrier_cbs * sizeof(barrier_cbs_tasks[0]),
GFP_KERNEL);
barrier_cbs_wq =
kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]),
GFP_KERNEL);
if (barrier_cbs_tasks == NULL || barrier_cbs_wq == 0)
return -ENOMEM;
for (i = 0; i < n_barrier_cbs; i++) {
init_waitqueue_head(&barrier_cbs_wq[i]);
barrier_cbs_tasks[i] = kthread_run(rcu_torture_barrier_cbs,
(void *)(long)i,
"rcu_torture_barrier_cbs");
if (IS_ERR(barrier_cbs_tasks[i])) {
ret = PTR_ERR(barrier_cbs_tasks[i]);
VERBOSE_PRINTK_ERRSTRING("Failed to create rcu_torture_barrier_cbs");
barrier_cbs_tasks[i] = NULL;
return ret;
}
}
barrier_task = kthread_run(rcu_torture_barrier, NULL,
"rcu_torture_barrier");
if (IS_ERR(barrier_task)) {
ret = PTR_ERR(barrier_task);
VERBOSE_PRINTK_ERRSTRING("Failed to create rcu_torture_barrier");
barrier_task = NULL;
}
return 0;
}
/* Clean up after RCU barrier testing. */
static void rcu_torture_barrier_cleanup(void)
{
int i;
if (barrier_task != NULL) {
VERBOSE_PRINTK_STRING("Stopping rcu_torture_barrier task");
kthread_stop(barrier_task);
barrier_task = NULL;
}
if (barrier_cbs_tasks != NULL) {
for (i = 0; i < n_barrier_cbs; i++) {
if (barrier_cbs_tasks[i] != NULL) {
VERBOSE_PRINTK_STRING("Stopping rcu_torture_barrier_cbs task");
kthread_stop(barrier_cbs_tasks[i]);
barrier_cbs_tasks[i] = NULL;
}
}
kfree(barrier_cbs_tasks);
barrier_cbs_tasks = NULL;
}
if (barrier_cbs_wq != NULL) {
kfree(barrier_cbs_wq);
barrier_cbs_wq = NULL;
}
}
static int rcutorture_cpu_notify(struct notifier_block *self,
@ -1598,6 +1808,7 @@ rcu_torture_cleanup(void)
fullstop = FULLSTOP_RMMOD;
mutex_unlock(&fullstop_mutex);
unregister_reboot_notifier(&rcutorture_shutdown_nb);
rcu_torture_barrier_cleanup();
rcu_torture_stall_cleanup();
if (stutter_task) {
VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
@ -1665,6 +1876,7 @@ rcu_torture_cleanup(void)
VERBOSE_PRINTK_STRING("Stopping rcu_torture_shutdown task");
kthread_stop(shutdown_task);
}
shutdown_task = NULL;
rcu_torture_onoff_cleanup();
/* Wait for all RCU callbacks to fire. */
@ -1676,7 +1888,7 @@ rcu_torture_cleanup(void)
if (cur_ops->cleanup)
cur_ops->cleanup();
if (atomic_read(&n_rcu_torture_error))
if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
else if (n_online_successes != n_online_attempts ||
n_offline_successes != n_offline_attempts)
@ -1692,10 +1904,12 @@ rcu_torture_init(void)
int i;
int cpu;
int firsterr = 0;
int retval;
static struct rcu_torture_ops *torture_ops[] =
{ &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
&rcu_bh_ops, &rcu_bh_sync_ops, &rcu_bh_expedited_ops,
&srcu_ops, &srcu_raw_ops, &srcu_expedited_ops,
&srcu_ops, &srcu_sync_ops, &srcu_raw_ops,
&srcu_raw_sync_ops, &srcu_expedited_ops,
&sched_ops, &sched_sync_ops, &sched_expedited_ops, };
mutex_lock(&fullstop_mutex);
@ -1749,6 +1963,7 @@ rcu_torture_init(void)
atomic_set(&n_rcu_torture_free, 0);
atomic_set(&n_rcu_torture_mberror, 0);
atomic_set(&n_rcu_torture_error, 0);
n_rcu_torture_barrier_error = 0;
n_rcu_torture_boost_ktrerror = 0;
n_rcu_torture_boost_rterror = 0;
n_rcu_torture_boost_failure = 0;
@ -1872,7 +2087,6 @@ rcu_torture_init(void)
test_boost_duration = 2;
if ((test_boost == 1 && cur_ops->can_boost) ||
test_boost == 2) {
int retval;
boost_starttime = jiffies + test_boost_interval * HZ;
register_cpu_notifier(&rcutorture_cpu_nb);
@ -1897,9 +2111,22 @@ rcu_torture_init(void)
goto unwind;
}
}
rcu_torture_onoff_init();
i = rcu_torture_onoff_init();
if (i != 0) {
firsterr = i;
goto unwind;
}
register_reboot_notifier(&rcutorture_shutdown_nb);
rcu_torture_stall_init();
i = rcu_torture_stall_init();
if (i != 0) {
firsterr = i;
goto unwind;
}
retval = rcu_torture_barrier_init();
if (retval != 0) {
firsterr = retval;
goto unwind;
}
rcutorture_record_test_transition();
mutex_unlock(&fullstop_mutex);
return 0;

35
kernel/rcutree.c
Просмотреть файл

@ -201,7 +201,6 @@ void rcu_note_context_switch(int cpu)
{
trace_rcu_utilization("Start context switch");
rcu_sched_qs(cpu);
rcu_preempt_note_context_switch(cpu);
trace_rcu_utilization("End context switch");
}
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
@ -1953,6 +1952,38 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
}
EXPORT_SYMBOL_GPL(call_rcu_bh);
/*
* Because a context switch is a grace period for RCU-sched and RCU-bh,
* any blocking grace-period wait automatically implies a grace period
* if there is only one CPU online at any point time during execution
* of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
* occasionally incorrectly indicate that there are multiple CPUs online
* when there was in fact only one the whole time, as this just adds
* some overhead: RCU still operates correctly.
*
* Of course, sampling num_online_cpus() with preemption enabled can
* give erroneous results if there are concurrent CPU-hotplug operations.
* For example, given a demonic sequence of preemptions in num_online_cpus()
* and CPU-hotplug operations, there could be two or more CPUs online at
* all times, but num_online_cpus() might well return one (or even zero).
*
* However, all such demonic sequences require at least one CPU-offline
* operation. Furthermore, rcu_blocking_is_gp() giving the wrong answer
* is only a problem if there is an RCU read-side critical section executing
* throughout. But RCU-sched and RCU-bh read-side critical sections
* disable either preemption or bh, which prevents a CPU from going offline.
* Therefore, the only way that rcu_blocking_is_gp() can incorrectly return
* that there is only one CPU when in fact there was more than one throughout
* is when there were no RCU readers in the system. If there are no
* RCU readers, the grace period by definition can be of zero length,
* regardless of the number of online CPUs.
*/
static inline int rcu_blocking_is_gp(void)
{
might_sleep(); /* Check for RCU read-side critical section. */
return num_online_cpus() <= 1;
}
/**
* synchronize_sched - wait until an rcu-sched grace period has elapsed.
*
@ -2543,7 +2574,7 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
for (i = NUM_RCU_LVLS - 1; i > 0; i--)
rsp->levelspread[i] = CONFIG_RCU_FANOUT;
rsp->levelspread[0] = RCU_FANOUT_LEAF;
rsp->levelspread[0] = CONFIG_RCU_FANOUT_LEAF;
}
#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
static void __init rcu_init_levelspread(struct rcu_state *rsp)

11
kernel/rcutree.h
Просмотреть файл

@ -29,18 +29,14 @@
#include <linux/seqlock.h>
/*
* Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
* Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
* CONFIG_RCU_FANOUT_LEAF.
* In theory, it should be possible to add more levels straightforwardly.
* In practice, this did work well going from three levels to four.
* Of course, your mileage may vary.
*/
#define MAX_RCU_LVLS 4
#if CONFIG_RCU_FANOUT > 16
#define RCU_FANOUT_LEAF 16
#else /* #if CONFIG_RCU_FANOUT > 16 */
#define RCU_FANOUT_LEAF (CONFIG_RCU_FANOUT)
#endif /* #else #if CONFIG_RCU_FANOUT > 16 */
#define RCU_FANOUT_1 (RCU_FANOUT_LEAF)
#define RCU_FANOUT_1 (CONFIG_RCU_FANOUT_LEAF)
#define RCU_FANOUT_2 (RCU_FANOUT_1 * CONFIG_RCU_FANOUT)
#define RCU_FANOUT_3 (RCU_FANOUT_2 * CONFIG_RCU_FANOUT)
#define RCU_FANOUT_4 (RCU_FANOUT_3 * CONFIG_RCU_FANOUT)
@ -434,7 +430,6 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
/* Forward declarations for rcutree_plugin.h */
static void rcu_bootup_announce(void);
long rcu_batches_completed(void);
static void rcu_preempt_note_context_switch(int cpu);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,

30
kernel/rcutree_plugin.h
Просмотреть файл

@ -153,7 +153,7 @@ static void rcu_preempt_qs(int cpu)
*
* Caller must disable preemption.
*/
static void rcu_preempt_note_context_switch(int cpu)
void rcu_preempt_note_context_switch(void)
{
struct task_struct *t = current;
unsigned long flags;
@ -164,7 +164,7 @@ static void rcu_preempt_note_context_switch(int cpu)
(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
/* Possibly blocking in an RCU read-side critical section. */
rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
rdp = __this_cpu_ptr(rcu_preempt_state.rda);
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
@ -228,7 +228,7 @@ static void rcu_preempt_note_context_switch(int cpu)
* means that we continue to block the current grace period.
*/
local_irq_save(flags);
rcu_preempt_qs(cpu);
rcu_preempt_qs(smp_processor_id());
local_irq_restore(flags);
}
@ -969,22 +969,6 @@ static void __init __rcu_init_preempt(void)
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data);
}
/*
* Check for a task exiting while in a preemptible-RCU read-side
* critical section, clean up if so. No need to issue warnings,
* as debug_check_no_locks_held() already does this if lockdep
* is enabled.
*/
void exit_rcu(void)
{
struct task_struct *t = current;
if (t->rcu_read_lock_nesting == 0)
return;
t->rcu_read_lock_nesting = 1;
__rcu_read_unlock();
}
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
static struct rcu_state *rcu_state = &rcu_sched_state;
@ -1017,14 +1001,6 @@ void rcu_force_quiescent_state(void)
}
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
/*
* Because preemptible RCU does not exist, we never have to check for
* CPUs being in quiescent states.
*/
static void rcu_preempt_note_context_switch(int cpu)
{
}
/*
* Because preemptible RCU does not exist, there are never any preempted
* RCU readers.

1
kernel/sched/core.c
Просмотреть файл

@ -2083,6 +2083,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
#endif
/* Here we just switch the register state and the stack. */
rcu_switch_from(prev);
switch_to(prev, next, prev);
barrier();

548
kernel/srcu.c
Просмотреть файл

@ -34,10 +34,77 @@
#include <linux/delay.h>
#include <linux/srcu.h>
/*
* Initialize an rcu_batch structure to empty.
*/
static inline void rcu_batch_init(struct rcu_batch *b)
{
b->head = NULL;
b->tail = &b->head;
}
/*
* Enqueue a callback onto the tail of the specified rcu_batch structure.
*/
static inline void rcu_batch_queue(struct rcu_batch *b, struct rcu_head *head)
{
*b->tail = head;
b->tail = &head->next;
}
/*
* Is the specified rcu_batch structure empty?
*/
static inline bool rcu_batch_empty(struct rcu_batch *b)
{
return b->tail == &b->head;
}
/*
* Remove the callback at the head of the specified rcu_batch structure
* and return a pointer to it, or return NULL if the structure is empty.
*/
static inline struct rcu_head *rcu_batch_dequeue(struct rcu_batch *b)
{
struct rcu_head *head;
if (rcu_batch_empty(b))
return NULL;
head = b->head;
b->head = head->next;
if (b->tail == &head->next)
rcu_batch_init(b);
return head;
}
/*
* Move all callbacks from the rcu_batch structure specified by "from" to
* the structure specified by "to".
*/
static inline void rcu_batch_move(struct rcu_batch *to, struct rcu_batch *from)
{
if (!rcu_batch_empty(from)) {
*to->tail = from->head;
to->tail = from->tail;
rcu_batch_init(from);
}
}
/* single-thread state-machine */
static void process_srcu(struct work_struct *work);
static int init_srcu_struct_fields(struct srcu_struct *sp)
{
sp->completed = 0;
mutex_init(&sp->mutex);
spin_lock_init(&sp->queue_lock);
sp->running = false;
rcu_batch_init(&sp->batch_queue);
rcu_batch_init(&sp->batch_check0);
rcu_batch_init(&sp->batch_check1);
rcu_batch_init(&sp->batch_done);
INIT_DELAYED_WORK(&sp->work, process_srcu);
sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
return sp->per_cpu_ref ? 0 : -ENOMEM;
}
@ -73,21 +140,116 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
/*
* srcu_readers_active_idx -- returns approximate number of readers
* active on the specified rank of per-CPU counters.
* Returns approximate total of the readers' ->seq[] values for the
* rank of per-CPU counters specified by idx.
*/
static int srcu_readers_active_idx(struct srcu_struct *sp, int idx)
static unsigned long srcu_readers_seq_idx(struct srcu_struct *sp, int idx)
{
int cpu;
int sum;
unsigned long sum = 0;
unsigned long t;
sum = 0;
for_each_possible_cpu(cpu)
sum += per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx];
for_each_possible_cpu(cpu) {
t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->seq[idx]);
sum += t;
}
return sum;
}
/*
* Returns approximate number of readers active on the specified rank
* of the per-CPU ->c[] counters.
*/
static unsigned long srcu_readers_active_idx(struct srcu_struct *sp, int idx)
{
int cpu;
unsigned long sum = 0;
unsigned long t;
for_each_possible_cpu(cpu) {
t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx]);
sum += t;
}
return sum;
}
/*
* Return true if the number of pre-existing readers is determined to
* be stably zero. An example unstable zero can occur if the call
* to srcu_readers_active_idx() misses an __srcu_read_lock() increment,
* but due to task migration, sees the corresponding __srcu_read_unlock()
* decrement. This can happen because srcu_readers_active_idx() takes
* time to sum the array, and might in fact be interrupted or preempted
* partway through the summation.
*/
static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
{
unsigned long seq;
seq = srcu_readers_seq_idx(sp, idx);
/*
* The following smp_mb() A pairs with the smp_mb() B located in
* __srcu_read_lock(). This pairing ensures that if an
* __srcu_read_lock() increments its counter after the summation
* in srcu_readers_active_idx(), then the corresponding SRCU read-side
* critical section will see any changes made prior to the start
* of the current SRCU grace period.
*
* Also, if the above call to srcu_readers_seq_idx() saw the
* increment of ->seq[], then the call to srcu_readers_active_idx()
* must see the increment of ->c[].
*/
smp_mb(); /* A */
/*
* Note that srcu_readers_active_idx() can incorrectly return
* zero even though there is a pre-existing reader throughout.
* To see this, suppose that task A is in a very long SRCU
* read-side critical section that started on CPU 0, and that
* no other reader exists, so that the sum of the counters
* is equal to one. Then suppose that task B starts executing
* srcu_readers_active_idx(), summing up to CPU 1, and then that
* task C starts reading on CPU 0, so that its increment is not
* summed, but finishes reading on CPU 2, so that its decrement
* -is- summed. Then when task B completes its sum, it will
* incorrectly get zero, despite the fact that task A has been
* in its SRCU read-side critical section the whole time.
*
* We therefore do a validation step should srcu_readers_active_idx()
* return zero.
*/
if (srcu_readers_active_idx(sp, idx) != 0)
return false;
/*
* The remainder of this function is the validation step.
* The following smp_mb() D pairs with the smp_mb() C in
* __srcu_read_unlock(). If the __srcu_read_unlock() was seen
* by srcu_readers_active_idx() above, then any destructive
* operation performed after the grace period will happen after
* the corresponding SRCU read-side critical section.
*
* Note that there can be at most NR_CPUS worth of readers using
* the old index, which is not enough to overflow even a 32-bit
* integer. (Yes, this does mean that systems having more than
* a billion or so CPUs need to be 64-bit systems.) Therefore,
* the sum of the ->seq[] counters cannot possibly overflow.
* Therefore, the only way that the return values of the two
* calls to srcu_readers_seq_idx() can be equal is if there were
* no increments of the corresponding rank of ->seq[] counts
* in the interim. But the missed-increment scenario laid out
* above includes an increment of the ->seq[] counter by
* the corresponding __srcu_read_lock(). Therefore, if this
* scenario occurs, the return values from the two calls to
* srcu_readers_seq_idx() will differ, and thus the validation
* step below suffices.
*/
smp_mb(); /* D */
return srcu_readers_seq_idx(sp, idx) == seq;
}
/**
* srcu_readers_active - returns approximate number of readers.
* @sp: which srcu_struct to count active readers (holding srcu_read_lock).
@ -98,7 +260,14 @@ static int srcu_readers_active_idx(struct srcu_struct *sp, int idx)
*/
static int srcu_readers_active(struct srcu_struct *sp)
{
return srcu_readers_active_idx(sp, 0) + srcu_readers_active_idx(sp, 1);
int cpu;
unsigned long sum = 0;
for_each_possible_cpu(cpu) {
sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]);
sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]);
}
return sum;
}
/**
@ -131,10 +300,11 @@ int __srcu_read_lock(struct srcu_struct *sp)
int idx;
preempt_disable();
idx = sp->completed & 0x1;
barrier(); /* ensure compiler looks -once- at sp->completed. */
per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]++;
srcu_barrier(); /* ensure compiler won't misorder critical section. */
idx = rcu_dereference_index_check(sp->completed,
rcu_read_lock_sched_held()) & 0x1;
ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1;
smp_mb(); /* B */ /* Avoid leaking the critical section. */
ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1;
preempt_enable();
return idx;
}
@ -149,8 +319,8 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
void __srcu_read_unlock(struct srcu_struct *sp, int idx)
{
preempt_disable();
srcu_barrier(); /* ensure compiler won't misorder critical section. */
per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
smp_mb(); /* C */ /* Avoid leaking the critical section. */
ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) -= 1;
preempt_enable();
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@ -163,14 +333,86 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
* we repeatedly block for 1-millisecond time periods. This approach
* has done well in testing, so there is no need for a config parameter.
*/
#define SYNCHRONIZE_SRCU_READER_DELAY 10
#define SRCU_RETRY_CHECK_DELAY 5
#define SYNCHRONIZE_SRCU_TRYCOUNT 2
#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT 12
/*
* @@@ Wait until all pre-existing readers complete. Such readers
* will have used the index specified by "idx".
* the caller should ensures the ->completed is not changed while checking
* and idx = (->completed & 1) ^ 1
*/
static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount)
{
for (;;) {
if (srcu_readers_active_idx_check(sp, idx))
return true;
if (--trycount <= 0)
return false;
udelay(SRCU_RETRY_CHECK_DELAY);
}
}
/*
* Increment the ->completed counter so that future SRCU readers will
* use the other rank of the ->c[] and ->seq[] arrays. This allows
* us to wait for pre-existing readers in a starvation-free manner.
*/
static void srcu_flip(struct srcu_struct *sp)
{
sp->completed++;
}
/*
* Enqueue an SRCU callback on the specified srcu_struct structure,
* initiating grace-period processing if it is not already running.
*/
void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
void (*func)(struct rcu_head *head))
{
unsigned long flags;
head->next = NULL;
head->func = func;
spin_lock_irqsave(&sp->queue_lock, flags);
rcu_batch_queue(&sp->batch_queue, head);
if (!sp->running) {
sp->running = true;
queue_delayed_work(system_nrt_wq, &sp->work, 0);
}
spin_unlock_irqrestore(&sp->queue_lock, flags);
}
EXPORT_SYMBOL_GPL(call_srcu);
struct rcu_synchronize {
struct rcu_head head;
struct completion completion;
};
/*
* Awaken the corresponding synchronize_srcu() instance now that a
* grace period has elapsed.
*/
static void wakeme_after_rcu(struct rcu_head *head)
{
struct rcu_synchronize *rcu;
rcu = container_of(head, struct rcu_synchronize, head);
complete(&rcu->completion);
}
static void srcu_advance_batches(struct srcu_struct *sp, int trycount);
static void srcu_reschedule(struct srcu_struct *sp);
/*
* Helper function for synchronize_srcu() and synchronize_srcu_expedited().
*/
static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
{
int idx;
struct rcu_synchronize rcu;
struct rcu_head *head = &rcu.head;
bool done = false;
rcu_lockdep_assert(!lock_is_held(&sp->dep_map) &&
!lock_is_held(&rcu_bh_lock_map) &&
@ -178,91 +420,32 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
!lock_is_held(&rcu_sched_lock_map),
"Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section");
idx = sp->completed;
mutex_lock(&sp->mutex);
init_completion(&rcu.completion);
/*
* Check to see if someone else did the work for us while we were
* waiting to acquire the lock. We need -two- advances of
* the counter, not just one. If there was but one, we might have
* shown up -after- our helper's first synchronize_sched(), thus
* having failed to prevent CPU-reordering races with concurrent
* srcu_read_unlock()s on other CPUs (see comment below). So we
* either (1) wait for two or (2) supply the second ourselves.
*/
head->next = NULL;
head->func = wakeme_after_rcu;
spin_lock_irq(&sp->queue_lock);
if (!sp->running) {
/* steal the processing owner */
sp->running = true;
rcu_batch_queue(&sp->batch_check0, head);
spin_unlock_irq(&sp->queue_lock);
if ((sp->completed - idx) >= 2) {
mutex_unlock(&sp->mutex);
return;
srcu_advance_batches(sp, trycount);
if (!rcu_batch_empty(&sp->batch_done)) {
BUG_ON(sp->batch_done.head != head);
rcu_batch_dequeue(&sp->batch_done);
done = true;
}
/* give the processing owner to work_struct */
srcu_reschedule(sp);
} else {
rcu_batch_queue(&sp->batch_queue, head);
spin_unlock_irq(&sp->queue_lock);
}
sync_func(); /* Force memory barrier on all CPUs. */
/*
* The preceding synchronize_sched() ensures that any CPU that
* sees the new value of sp->completed will also see any preceding
* changes to data structures made by this CPU. This prevents
* some other CPU from reordering the accesses in its SRCU
* read-side critical section to precede the corresponding
* srcu_read_lock() -- ensuring that such references will in
* fact be protected.
*
* So it is now safe to do the flip.
*/
idx = sp->completed & 0x1;
sp->completed++;
sync_func(); /* Force memory barrier on all CPUs. */
/*
* At this point, because of the preceding synchronize_sched(),
* all srcu_read_lock() calls using the old counters have completed.
* Their corresponding critical sections might well be still
* executing, but the srcu_read_lock() primitives themselves
* will have finished executing. We initially give readers
* an arbitrarily chosen 10 microseconds to get out of their
* SRCU read-side critical sections, then loop waiting 1/HZ
* seconds per iteration. The 10-microsecond value has done
* very well in testing.
*/
if (srcu_readers_active_idx(sp, idx))
udelay(SYNCHRONIZE_SRCU_READER_DELAY);
while (srcu_readers_active_idx(sp, idx))
schedule_timeout_interruptible(1);
sync_func(); /* Force memory barrier on all CPUs. */
/*
* The preceding synchronize_sched() forces all srcu_read_unlock()
* primitives that were executing concurrently with the preceding
* for_each_possible_cpu() loop to have completed by this point.
* More importantly, it also forces the corresponding SRCU read-side
* critical sections to have also completed, and the corresponding
* references to SRCU-protected data items to be dropped.
*
* Note:
*
* Despite what you might think at first glance, the
* preceding synchronize_sched() -must- be within the
* critical section ended by the following mutex_unlock().
* Otherwise, a task taking the early exit can race
* with a srcu_read_unlock(), which might have executed
* just before the preceding srcu_readers_active() check,
* and whose CPU might have reordered the srcu_read_unlock()
* with the preceding critical section. In this case, there
* is nothing preventing the synchronize_sched() task that is
* taking the early exit from freeing a data structure that
* is still being referenced (out of order) by the task
* doing the srcu_read_unlock().
*
* Alternatively, the comparison with "2" on the early exit
* could be changed to "3", but this increases synchronize_srcu()
* latency for bulk loads. So the current code is preferred.
*/
mutex_unlock(&sp->mutex);
if (!done)
wait_for_completion(&rcu.completion);
}
/**
@ -281,7 +464,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
*/
void synchronize_srcu(struct srcu_struct *sp)
{
__synchronize_srcu(sp, synchronize_sched);
__synchronize_srcu(sp, SYNCHRONIZE_SRCU_TRYCOUNT);
}
EXPORT_SYMBOL_GPL(synchronize_srcu);
@ -289,18 +472,11 @@ EXPORT_SYMBOL_GPL(synchronize_srcu);
* synchronize_srcu_expedited - Brute-force SRCU grace period
* @sp: srcu_struct with which to synchronize.
*
* Wait for an SRCU grace period to elapse, but use a "big hammer"
* approach to force the grace period to end quickly. This consumes
* significant time on all CPUs and is unfriendly to real-time workloads,
* so is thus not recommended for any sort of common-case code. In fact,
* if you are using synchronize_srcu_expedited() in a loop, please
* restructure your code to batch your updates, and then use a single
* synchronize_srcu() instead.
* Wait for an SRCU grace period to elapse, but be more aggressive about
* spinning rather than blocking when waiting.
*
* Note that it is illegal to call this function while holding any lock
* that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
* to call this function from a CPU-hotplug notifier. Failing to observe
* these restriction will result in deadlock. It is also illegal to call
* that is acquired by a CPU-hotplug notifier. It is also illegal to call
* synchronize_srcu_expedited() from the corresponding SRCU read-side
* critical section; doing so will result in deadlock. However, it is
* perfectly legal to call synchronize_srcu_expedited() on one srcu_struct
@ -309,10 +485,19 @@ EXPORT_SYMBOL_GPL(synchronize_srcu);
*/
void synchronize_srcu_expedited(struct srcu_struct *sp)
{
__synchronize_srcu(sp, synchronize_sched_expedited);
__synchronize_srcu(sp, SYNCHRONIZE_SRCU_EXP_TRYCOUNT);
}
EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
/**
* srcu_barrier - Wait until all in-flight call_srcu() callbacks complete.
*/
void srcu_barrier(struct srcu_struct *sp)
{
synchronize_srcu(sp);
}
EXPORT_SYMBOL_GPL(srcu_barrier);
/**
* srcu_batches_completed - return batches completed.
* @sp: srcu_struct on which to report batch completion.
@ -320,9 +505,146 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
* Report the number of batches, correlated with, but not necessarily
* precisely the same as, the number of grace periods that have elapsed.
*/
long srcu_batches_completed(struct srcu_struct *sp)
{
return sp->completed;
}
EXPORT_SYMBOL_GPL(srcu_batches_completed);
#define SRCU_CALLBACK_BATCH 10
#define SRCU_INTERVAL 1
/*
* Move any new SRCU callbacks to the first stage of the SRCU grace
* period pipeline.
*/
static void srcu_collect_new(struct srcu_struct *sp)
{
if (!rcu_batch_empty(&sp->batch_queue)) {
spin_lock_irq(&sp->queue_lock);
rcu_batch_move(&sp->batch_check0, &sp->batch_queue);
spin_unlock_irq(&sp->queue_lock);
}
}
/*
* Core SRCU state machine. Advance callbacks from ->batch_check0 to
* ->batch_check1 and then to ->batch_done as readers drain.
*/
static void srcu_advance_batches(struct srcu_struct *sp, int trycount)
{
int idx = 1 ^ (sp->completed & 1);
/*
* Because readers might be delayed for an extended period after
* fetching ->completed for their index, at any point in time there
* might well be readers using both idx=0 and idx=1. We therefore
* need to wait for readers to clear from both index values before
* invoking a callback.
*/
if (rcu_batch_empty(&sp->batch_check0) &&
rcu_batch_empty(&sp->batch_check1))
return; /* no callbacks need to be advanced */
if (!try_check_zero(sp, idx, trycount))
return; /* failed to advance, will try after SRCU_INTERVAL */
/*
* The callbacks in ->batch_check1 have already done with their
* first zero check and flip back when they were enqueued on
* ->batch_check0 in a previous invocation of srcu_advance_batches().
* (Presumably try_check_zero() returned false during that
* invocation, leaving the callbacks stranded on ->batch_check1.)
* They are therefore ready to invoke, so move them to ->batch_done.
*/
rcu_batch_move(&sp->batch_done, &sp->batch_check1);
if (rcu_batch_empty(&sp->batch_check0))
return; /* no callbacks need to be advanced */
srcu_flip(sp);
/*
* The callbacks in ->batch_check0 just finished their
* first check zero and flip, so move them to ->batch_check1
* for future checking on the other idx.
*/
rcu_batch_move(&sp->batch_check1, &sp->batch_check0);
/*
* SRCU read-side critical sections are normally short, so check
* at least twice in quick succession after a flip.
*/
trycount = trycount < 2 ? 2 : trycount;
if (!try_check_zero(sp, idx^1, trycount))
return; /* failed to advance, will try after SRCU_INTERVAL */
/*
* The callbacks in ->batch_check1 have now waited for all
* pre-existing readers using both idx values. They are therefore
* ready to invoke, so move them to ->batch_done.
*/
rcu_batch_move(&sp->batch_done, &sp->batch_check1);
}
/*
* Invoke a limited number of SRCU callbacks that have passed through
* their grace period. If there are more to do, SRCU will reschedule
* the workqueue.
*/
static void srcu_invoke_callbacks(struct srcu_struct *sp)
{
int i;
struct rcu_head *head;
for (i = 0; i < SRCU_CALLBACK_BATCH; i++) {
head = rcu_batch_dequeue(&sp->batch_done);
if (!head)
break;
local_bh_disable();
head->func(head);
local_bh_enable();
}
}
/*
* Finished one round of SRCU grace period. Start another if there are
* more SRCU callbacks queued, otherwise put SRCU into not-running state.
*/
static void srcu_reschedule(struct srcu_struct *sp)
{
bool pending = true;
if (rcu_batch_empty(&sp->batch_done) &&
rcu_batch_empty(&sp->batch_check1) &&
rcu_batch_empty(&sp->batch_check0) &&
rcu_batch_empty(&sp->batch_queue)) {
spin_lock_irq(&sp->queue_lock);
if (rcu_batch_empty(&sp->batch_done) &&
rcu_batch_empty(&sp->batch_check1) &&
rcu_batch_empty(&sp->batch_check0) &&
rcu_batch_empty(&sp->batch_queue)) {
sp->running = false;
pending = false;
}
spin_unlock_irq(&sp->queue_lock);
}
if (pending)
queue_delayed_work(system_nrt_wq, &sp->work, SRCU_INTERVAL);
}
/*
* This is the work-queue function that handles SRCU grace periods.
*/
static void process_srcu(struct work_struct *work)
{
struct srcu_struct *sp;
sp = container_of(work, struct srcu_struct, work.work);
srcu_collect_new(sp);
srcu_advance_batches(sp, 1);
srcu_invoke_callbacks(sp);
srcu_reschedule(sp);
}

8
kernel/timer.c
Просмотреть файл

@ -861,7 +861,13 @@ EXPORT_SYMBOL(mod_timer);
*
* mod_timer_pinned() is a way to update the expire field of an
* active timer (if the timer is inactive it will be activated)
* and not allow the timer to be migrated to a different CPU.
* and to ensure that the timer is scheduled on the current CPU.
*
* Note that this does not prevent the timer from being migrated
* when the current CPU goes offline. If this is a problem for
* you, use CPU-hotplug notifiers to handle it correctly, for
* example, cancelling the timer when the corresponding CPU goes
* offline.
*
* mod_timer_pinned(timer, expires) is equivalent to:
*

22
lib/list_debug.c
Просмотреть файл

@ -10,6 +10,7 @@
#include <linux/list.h>
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/rculist.h>
/*
* Insert a new entry between two known consecutive entries.
@ -75,3 +76,24 @@ void list_del(struct list_head *entry)
entry->prev = LIST_POISON2;
}
EXPORT_SYMBOL(list_del);
/*
* RCU variants.
*/
void __list_add_rcu(struct list_head *new,
struct list_head *prev, struct list_head *next)
{
WARN(next->prev != prev,
"list_add_rcu corruption. next->prev should be "
"prev (%p), but was %p. (next=%p).\n",
prev, next->prev, next);
WARN(prev->next != next,
"list_add_rcu corruption. prev->next should be "
"next (%p), but was %p. (prev=%p).\n",
next, prev->next, prev);
new->next = next;
new->prev = prev;
rcu_assign_pointer(list_next_rcu(prev), new);
next->prev = new;
}
EXPORT_SYMBOL(__list_add_rcu);