seqlock: Add kernel-doc for seqcount_t and seqlock_t APIs
seqlock.h is now included by kernel's RST documentation, but a small number of the the exported seqlock.h functions are kernel-doc annotated. Add kernel-doc for all seqlock.h exported APIs. Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200720155530.1173732-6-a.darwish@linutronix.de
This commit is contained in:
Ahmed S. Darwish
Peter Zijlstra
Родитель
f4a27cbcec
Коммит
89b88845e0
|
|
@ -75,6 +75,10 @@ static inline void __seqcount_init(seqcount_t *s, const char *name,
|
|||
# define SEQCOUNT_DEP_MAP_INIT(lockname) \
|
||||
.dep_map = { .name = #lockname } \
|
||||
|
||||
/**
|
||||
* seqcount_init() - runtime initializer for seqcount_t
|
||||
* @s: Pointer to the seqcount_t instance
|
||||
*/
|
||||
# define seqcount_init(s) \
|
||||
do { \
|
||||
static struct lock_class_key __key; \
|
||||
|
|
@ -98,13 +102,15 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s)
|
|||
# define seqcount_lockdep_reader_access(x)
|
||||
#endif
|
||||
|
||||
#define SEQCNT_ZERO(lockname) { .sequence = 0, SEQCOUNT_DEP_MAP_INIT(lockname)}
|
||||
|
||||
/**
|
||||
* SEQCNT_ZERO() - static initializer for seqcount_t
|
||||
* @name: Name of the seqcount_t instance
|
||||
*/
|
||||
#define SEQCNT_ZERO(name) { .sequence = 0, SEQCOUNT_DEP_MAP_INIT(name) }
|
||||
|
||||
/**
|
||||
* __read_seqcount_begin - begin a seq-read critical section (without barrier)
|
||||
* @s: pointer to seqcount_t
|
||||
* Returns: count to be passed to read_seqcount_retry
|
||||
* __read_seqcount_begin() - begin a seqcount_t read section w/o barrier
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* __read_seqcount_begin is like read_seqcount_begin, but has no smp_rmb()
|
||||
* barrier. Callers should ensure that smp_rmb() or equivalent ordering is
|
||||
|
|
@ -113,6 +119,8 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s)
|
|||
*
|
||||
* Use carefully, only in critical code, and comment how the barrier is
|
||||
* provided.
|
||||
*
|
||||
* Return: count to be passed to read_seqcount_retry()
|
||||
*/
|
||||
static inline unsigned __read_seqcount_begin(const seqcount_t *s)
|
||||
{
|
||||
|
|
@ -129,13 +137,10 @@ repeat:
|
|||
}
|
||||
|
||||
/**
|
||||
* raw_read_seqcount_begin - start seq-read critical section w/o lockdep
|
||||
* @s: pointer to seqcount_t
|
||||
* Returns: count to be passed to read_seqcount_retry
|
||||
* raw_read_seqcount_begin() - begin a seqcount_t read section w/o lockdep
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* raw_read_seqcount_begin opens a read critical section of the given
|
||||
* seqcount, but without any lockdep checking. Validity of the critical
|
||||
* section is tested by checking read_seqcount_retry function.
|
||||
* Return: count to be passed to read_seqcount_retry()
|
||||
*/
|
||||
static inline unsigned raw_read_seqcount_begin(const seqcount_t *s)
|
||||
{
|
||||
|
|
@ -145,13 +150,10 @@ static inline unsigned raw_read_seqcount_begin(const seqcount_t *s)
|
|||
}
|
||||
|
||||
/**
|
||||
* read_seqcount_begin - begin a seq-read critical section
|
||||
* @s: pointer to seqcount_t
|
||||
* Returns: count to be passed to read_seqcount_retry
|
||||
* read_seqcount_begin() - begin a seqcount_t read critical section
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* read_seqcount_begin opens a read critical section of the given seqcount.
|
||||
* Validity of the critical section is tested by checking read_seqcount_retry
|
||||
* function.
|
||||
* Return: count to be passed to read_seqcount_retry()
|
||||
*/
|
||||
static inline unsigned read_seqcount_begin(const seqcount_t *s)
|
||||
{
|
||||
|
|
@ -160,13 +162,15 @@ static inline unsigned read_seqcount_begin(const seqcount_t *s)
|
|||
}
|
||||
|
||||
/**
|
||||
* raw_read_seqcount - Read the raw seqcount
|
||||
* @s: pointer to seqcount_t
|
||||
* Returns: count to be passed to read_seqcount_retry
|
||||
* raw_read_seqcount() - read the raw seqcount_t counter value
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* raw_read_seqcount opens a read critical section of the given
|
||||
* seqcount without any lockdep checking and without checking or
|
||||
* masking the LSB. Calling code is responsible for handling that.
|
||||
* seqcount_t, without any lockdep checking, and without checking or
|
||||
* masking the sequence counter LSB. Calling code is responsible for
|
||||
* handling that.
|
||||
*
|
||||
* Return: count to be passed to read_seqcount_retry()
|
||||
*/
|
||||
static inline unsigned raw_read_seqcount(const seqcount_t *s)
|
||||
{
|
||||
|
|
@ -177,18 +181,21 @@ static inline unsigned raw_read_seqcount(const seqcount_t *s)
|
|||
}
|
||||
|
||||
/**
|
||||
* raw_seqcount_begin - begin a seq-read critical section
|
||||
* @s: pointer to seqcount_t
|
||||
* Returns: count to be passed to read_seqcount_retry
|
||||
* raw_seqcount_begin() - begin a seqcount_t read critical section w/o
|
||||
* lockdep and w/o counter stabilization
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* raw_seqcount_begin opens a read critical section of the given seqcount.
|
||||
* Validity of the critical section is tested by checking read_seqcount_retry
|
||||
* function.
|
||||
* raw_seqcount_begin opens a read critical section of the given
|
||||
* seqcount_t. Unlike read_seqcount_begin(), this function will not wait
|
||||
* for the count to stabilize. If a writer is active when it begins, it
|
||||
* will fail the read_seqcount_retry() at the end of the read critical
|
||||
* section instead of stabilizing at the beginning of it.
|
||||
*
|
||||
* Unlike read_seqcount_begin(), this function will not wait for the count
|
||||
* to stabilize. If a writer is active when we begin, we will fail the
|
||||
* read_seqcount_retry() instead of stabilizing at the beginning of the
|
||||
* critical section.
|
||||
* Use this only in special kernel hot paths where the read section is
|
||||
* small and has a high probability of success through other external
|
||||
* means. It will save a single branching instruction.
|
||||
*
|
||||
* Return: count to be passed to read_seqcount_retry()
|
||||
*/
|
||||
static inline unsigned raw_seqcount_begin(const seqcount_t *s)
|
||||
{
|
||||
|
|
@ -199,10 +206,9 @@ static inline unsigned raw_seqcount_begin(const seqcount_t *s)
|
|||
}
|
||||
|
||||
/**
|
||||
* __read_seqcount_retry - end a seq-read critical section (without barrier)
|
||||
* @s: pointer to seqcount_t
|
||||
* @start: count, from read_seqcount_begin
|
||||
* Returns: 1 if retry is required, else 0
|
||||
* __read_seqcount_retry() - end a seqcount_t read section w/o barrier
|
||||
* @s: Pointer to seqcount_t
|
||||
* @start: count, from read_seqcount_begin()
|
||||
*
|
||||
* __read_seqcount_retry is like read_seqcount_retry, but has no smp_rmb()
|
||||
* barrier. Callers should ensure that smp_rmb() or equivalent ordering is
|
||||
|
|
@ -211,6 +217,8 @@ static inline unsigned raw_seqcount_begin(const seqcount_t *s)
|
|||
*
|
||||
* Use carefully, only in critical code, and comment how the barrier is
|
||||
* provided.
|
||||
*
|
||||
* Return: true if a read section retry is required, else false
|
||||
*/
|
||||
static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
|
||||
{
|
||||
|
|
@ -219,14 +227,15 @@ static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
|
|||
}
|
||||
|
||||
/**
|
||||
* read_seqcount_retry - end a seq-read critical section
|
||||
* @s: pointer to seqcount_t
|
||||
* @start: count, from read_seqcount_begin
|
||||
* Returns: 1 if retry is required, else 0
|
||||
* read_seqcount_retry() - end a seqcount_t read critical section
|
||||
* @s: Pointer to seqcount_t
|
||||
* @start: count, from read_seqcount_begin()
|
||||
*
|
||||
* read_seqcount_retry closes a read critical section of the given seqcount.
|
||||
* If the critical section was invalid, it must be ignored (and typically
|
||||
* retried).
|
||||
* read_seqcount_retry closes the read critical section of given
|
||||
* seqcount_t. If the critical section was invalid, it must be ignored
|
||||
* (and typically retried).
|
||||
*
|
||||
* Return: true if a read section retry is required, else false
|
||||
*/
|
||||
static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
|
||||
{
|
||||
|
|
@ -234,6 +243,10 @@ static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
|
|||
return __read_seqcount_retry(s, start);
|
||||
}
|
||||
|
||||
/**
|
||||
* raw_write_seqcount_begin() - start a seqcount_t write section w/o lockdep
|
||||
* @s: Pointer to seqcount_t
|
||||
*/
|
||||
static inline void raw_write_seqcount_begin(seqcount_t *s)
|
||||
{
|
||||
kcsan_nestable_atomic_begin();
|
||||
|
|
@ -241,6 +254,10 @@ static inline void raw_write_seqcount_begin(seqcount_t *s)
|
|||
smp_wmb();
|
||||
}
|
||||
|
||||
/**
|
||||
* raw_write_seqcount_end() - end a seqcount_t write section w/o lockdep
|
||||
* @s: Pointer to seqcount_t
|
||||
*/
|
||||
static inline void raw_write_seqcount_end(seqcount_t *s)
|
||||
{
|
||||
smp_wmb();
|
||||
|
|
@ -248,17 +265,42 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
|
|||
kcsan_nestable_atomic_end();
|
||||
}
|
||||
|
||||
/**
|
||||
* write_seqcount_begin_nested() - start a seqcount_t write section with
|
||||
* custom lockdep nesting level
|
||||
* @s: Pointer to seqcount_t
|
||||
* @subclass: lockdep nesting level
|
||||
*
|
||||
* See Documentation/locking/lockdep-design.rst
|
||||
*/
|
||||
static inline void write_seqcount_begin_nested(seqcount_t *s, int subclass)
|
||||
{
|
||||
raw_write_seqcount_begin(s);
|
||||
seqcount_acquire(&s->dep_map, subclass, 0, _RET_IP_);
|
||||
}
|
||||
|
||||
/**
|
||||
* write_seqcount_begin() - start a seqcount_t write side critical section
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* write_seqcount_begin opens a write side critical section of the given
|
||||
* seqcount_t.
|
||||
*
|
||||
* Context: seqcount_t write side critical sections must be serialized and
|
||||
* non-preemptible. If readers can be invoked from hardirq or softirq
|
||||
* context, interrupts or bottom halves must be respectively disabled.
|
||||
*/
|
||||
static inline void write_seqcount_begin(seqcount_t *s)
|
||||
{
|
||||
write_seqcount_begin_nested(s, 0);
|
||||
}
|
||||
|
||||
/**
|
||||
* write_seqcount_end() - end a seqcount_t write side critical section
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* The write section must've been opened with write_seqcount_begin().
|
||||
*/
|
||||
static inline void write_seqcount_end(seqcount_t *s)
|
||||
{
|
||||
seqcount_release(&s->dep_map, _RET_IP_);
|
||||
|
|
@ -266,12 +308,12 @@ static inline void write_seqcount_end(seqcount_t *s)
|
|||
}
|
||||
|
||||
/**
|
||||
* raw_write_seqcount_barrier - do a seq write barrier
|
||||
* @s: pointer to seqcount_t
|
||||
* raw_write_seqcount_barrier() - do a seqcount_t write barrier
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* This can be used to provide an ordering guarantee instead of the
|
||||
* usual consistency guarantee. It is one wmb cheaper, because we can
|
||||
* collapse the two back-to-back wmb()s.
|
||||
* This can be used to provide an ordering guarantee instead of the usual
|
||||
* consistency guarantee. It is one wmb cheaper, because it can collapse
|
||||
* the two back-to-back wmb()s.
|
||||
*
|
||||
* Note that writes surrounding the barrier should be declared atomic (e.g.
|
||||
* via WRITE_ONCE): a) to ensure the writes become visible to other threads
|
||||
|
|
@ -316,11 +358,12 @@ static inline void raw_write_seqcount_barrier(seqcount_t *s)
|
|||
}
|
||||
|
||||
/**
|
||||
* write_seqcount_invalidate - invalidate in-progress read-side seq operations
|
||||
* @s: pointer to seqcount_t
|
||||
* write_seqcount_invalidate() - invalidate in-progress seqcount_t read
|
||||
* side operations
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* After write_seqcount_invalidate, no read-side seq operations will complete
|
||||
* successfully and see data older than this.
|
||||
* After write_seqcount_invalidate, no seqcount_t read side operations
|
||||
* will complete successfully and see data older than this.
|
||||
*/
|
||||
static inline void write_seqcount_invalidate(seqcount_t *s)
|
||||
{
|
||||
|
|
@ -330,6 +373,21 @@ static inline void write_seqcount_invalidate(seqcount_t *s)
|
|||
kcsan_nestable_atomic_end();
|
||||
}
|
||||
|
||||
/**
|
||||
* raw_read_seqcount_latch() - pick even/odd seqcount_t latch data copy
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* Use seqcount_t latching to switch between two storage places protected
|
||||
* by a sequence counter. Doing so allows having interruptible, preemptible,
|
||||
* seqcount_t write side critical sections.
|
||||
*
|
||||
* Check raw_write_seqcount_latch() for more details and a full reader and
|
||||
* writer usage example.
|
||||
*
|
||||
* Return: sequence counter raw value. Use the lowest bit as an index for
|
||||
* picking which data copy to read. The full counter value must then be
|
||||
* checked with read_seqcount_retry().
|
||||
*/
|
||||
static inline int raw_read_seqcount_latch(seqcount_t *s)
|
||||
{
|
||||
/* Pairs with the first smp_wmb() in raw_write_seqcount_latch() */
|
||||
|
|
@ -338,8 +396,8 @@ static inline int raw_read_seqcount_latch(seqcount_t *s)
|
|||
}
|
||||
|
||||
/**
|
||||
* raw_write_seqcount_latch - redirect readers to even/odd copy
|
||||
* @s: pointer to seqcount_t
|
||||
* raw_write_seqcount_latch() - redirect readers to even/odd copy
|
||||
* @s: Pointer to seqcount_t
|
||||
*
|
||||
* The latch technique is a multiversion concurrency control method that allows
|
||||
* queries during non-atomic modifications. If you can guarantee queries never
|
||||
|
|
@ -446,17 +504,28 @@ typedef struct {
|
|||
.lock = __SPIN_LOCK_UNLOCKED(lockname) \
|
||||
}
|
||||
|
||||
#define seqlock_init(x) \
|
||||
/**
|
||||
* seqlock_init() - dynamic initializer for seqlock_t
|
||||
* @sl: Pointer to the seqlock_t instance
|
||||
*/
|
||||
#define seqlock_init(sl) \
|
||||
do { \
|
||||
seqcount_init(&(x)->seqcount); \
|
||||
spin_lock_init(&(x)->lock); \
|
||||
seqcount_init(&(sl)->seqcount); \
|
||||
spin_lock_init(&(sl)->lock); \
|
||||
} while (0)
|
||||
|
||||
#define DEFINE_SEQLOCK(x) \
|
||||
seqlock_t x = __SEQLOCK_UNLOCKED(x)
|
||||
/**
|
||||
* DEFINE_SEQLOCK() - Define a statically allocated seqlock_t
|
||||
* @sl: Name of the seqlock_t instance
|
||||
*/
|
||||
#define DEFINE_SEQLOCK(sl) \
|
||||
seqlock_t sl = __SEQLOCK_UNLOCKED(sl)
|
||||
|
||||
/*
|
||||
* Read side functions for starting and finalizing a read side section.
|
||||
/**
|
||||
* read_seqbegin() - start a seqlock_t read side critical section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* Return: count, to be passed to read_seqretry()
|
||||
*/
|
||||
static inline unsigned read_seqbegin(const seqlock_t *sl)
|
||||
{
|
||||
|
|
@ -467,6 +536,17 @@ static inline unsigned read_seqbegin(const seqlock_t *sl)
|
|||
return ret;
|
||||
}
|
||||
|
||||
/**
|
||||
* read_seqretry() - end a seqlock_t read side section
|
||||
* @sl: Pointer to seqlock_t
|
||||
* @start: count, from read_seqbegin()
|
||||
*
|
||||
* read_seqretry closes the read side critical section of given seqlock_t.
|
||||
* If the critical section was invalid, it must be ignored (and typically
|
||||
* retried).
|
||||
*
|
||||
* Return: true if a read section retry is required, else false
|
||||
*/
|
||||
static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
|
||||
{
|
||||
/*
|
||||
|
|
@ -478,10 +558,18 @@ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
|
|||
return read_seqcount_retry(&sl->seqcount, start);
|
||||
}
|
||||
|
||||
/*
|
||||
* Lock out other writers and update the count.
|
||||
* Acts like a normal spin_lock/unlock.
|
||||
* Don't need preempt_disable() because that is in the spin_lock already.
|
||||
/**
|
||||
* write_seqlock() - start a seqlock_t write side critical section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* write_seqlock opens a write side critical section for the given
|
||||
* seqlock_t. It also implicitly acquires the spinlock_t embedded inside
|
||||
* that sequential lock. All seqlock_t write side sections are thus
|
||||
* automatically serialized and non-preemptible.
|
||||
*
|
||||
* Context: if the seqlock_t read section, or other write side critical
|
||||
* sections, can be invoked from hardirq or softirq contexts, use the
|
||||
* _irqsave or _bh variants of this function instead.
|
||||
*/
|
||||
static inline void write_seqlock(seqlock_t *sl)
|
||||
{
|
||||
|
|
@ -489,30 +577,66 @@ static inline void write_seqlock(seqlock_t *sl)
|
|||
write_seqcount_begin(&sl->seqcount);
|
||||
}
|
||||
|
||||
/**
|
||||
* write_sequnlock() - end a seqlock_t write side critical section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* write_sequnlock closes the (serialized and non-preemptible) write side
|
||||
* critical section of given seqlock_t.
|
||||
*/
|
||||
static inline void write_sequnlock(seqlock_t *sl)
|
||||
{
|
||||
write_seqcount_end(&sl->seqcount);
|
||||
spin_unlock(&sl->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* write_seqlock_bh() - start a softirqs-disabled seqlock_t write section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* _bh variant of write_seqlock(). Use only if the read side section, or
|
||||
* other write side sections, can be invoked from softirq contexts.
|
||||
*/
|
||||
static inline void write_seqlock_bh(seqlock_t *sl)
|
||||
{
|
||||
spin_lock_bh(&sl->lock);
|
||||
write_seqcount_begin(&sl->seqcount);
|
||||
}
|
||||
|
||||
/**
|
||||
* write_sequnlock_bh() - end a softirqs-disabled seqlock_t write section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* write_sequnlock_bh closes the serialized, non-preemptible, and
|
||||
* softirqs-disabled, seqlock_t write side critical section opened with
|
||||
* write_seqlock_bh().
|
||||
*/
|
||||
static inline void write_sequnlock_bh(seqlock_t *sl)
|
||||
{
|
||||
write_seqcount_end(&sl->seqcount);
|
||||
spin_unlock_bh(&sl->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* write_seqlock_irq() - start a non-interruptible seqlock_t write section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* _irq variant of write_seqlock(). Use only if the read side section, or
|
||||
* other write sections, can be invoked from hardirq contexts.
|
||||
*/
|
||||
static inline void write_seqlock_irq(seqlock_t *sl)
|
||||
{
|
||||
spin_lock_irq(&sl->lock);
|
||||
write_seqcount_begin(&sl->seqcount);
|
||||
}
|
||||
|
||||
/**
|
||||
* write_sequnlock_irq() - end a non-interruptible seqlock_t write section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* write_sequnlock_irq closes the serialized and non-interruptible
|
||||
* seqlock_t write side section opened with write_seqlock_irq().
|
||||
*/
|
||||
static inline void write_sequnlock_irq(seqlock_t *sl)
|
||||
{
|
||||
write_seqcount_end(&sl->seqcount);
|
||||
|
|
@ -528,9 +652,28 @@ static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl)
|
|||
return flags;
|
||||
}
|
||||
|
||||
/**
|
||||
* write_seqlock_irqsave() - start a non-interruptible seqlock_t write
|
||||
* section
|
||||
* @lock: Pointer to seqlock_t
|
||||
* @flags: Stack-allocated storage for saving caller's local interrupt
|
||||
* state, to be passed to write_sequnlock_irqrestore().
|
||||
*
|
||||
* _irqsave variant of write_seqlock(). Use it only if the read side
|
||||
* section, or other write sections, can be invoked from hardirq context.
|
||||
*/
|
||||
#define write_seqlock_irqsave(lock, flags) \
|
||||
do { flags = __write_seqlock_irqsave(lock); } while (0)
|
||||
|
||||
/**
|
||||
* write_sequnlock_irqrestore() - end non-interruptible seqlock_t write
|
||||
* section
|
||||
* @sl: Pointer to seqlock_t
|
||||
* @flags: Caller's saved interrupt state, from write_seqlock_irqsave()
|
||||
*
|
||||
* write_sequnlock_irqrestore closes the serialized and non-interruptible
|
||||
* seqlock_t write section previously opened with write_seqlock_irqsave().
|
||||
*/
|
||||
static inline void
|
||||
write_sequnlock_irqrestore(seqlock_t *sl, unsigned long flags)
|
||||
{
|
||||
|
|
@ -538,36 +681,79 @@ write_sequnlock_irqrestore(seqlock_t *sl, unsigned long flags)
|
|||
spin_unlock_irqrestore(&sl->lock, flags);
|
||||
}
|
||||
|
||||
/*
|
||||
* A locking reader exclusively locks out other writers and locking readers,
|
||||
* but doesn't update the sequence number. Acts like a normal spin_lock/unlock.
|
||||
* Don't need preempt_disable() because that is in the spin_lock already.
|
||||
/**
|
||||
* read_seqlock_excl() - begin a seqlock_t locking reader section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* read_seqlock_excl opens a seqlock_t locking reader critical section. A
|
||||
* locking reader exclusively locks out *both* other writers *and* other
|
||||
* locking readers, but it does not update the embedded sequence number.
|
||||
*
|
||||
* Locking readers act like a normal spin_lock()/spin_unlock().
|
||||
*
|
||||
* Context: if the seqlock_t write section, *or other read sections*, can
|
||||
* be invoked from hardirq or softirq contexts, use the _irqsave or _bh
|
||||
* variant of this function instead.
|
||||
*
|
||||
* The opened read section must be closed with read_sequnlock_excl().
|
||||
*/
|
||||
static inline void read_seqlock_excl(seqlock_t *sl)
|
||||
{
|
||||
spin_lock(&sl->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* read_sequnlock_excl() - end a seqlock_t locking reader critical section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*/
|
||||
static inline void read_sequnlock_excl(seqlock_t *sl)
|
||||
{
|
||||
spin_unlock(&sl->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* read_seqlock_excl_bh() - start a seqlock_t locking reader section with
|
||||
* softirqs disabled
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* _bh variant of read_seqlock_excl(). Use this variant only if the
|
||||
* seqlock_t write side section, *or other read sections*, can be invoked
|
||||
* from softirq contexts.
|
||||
*/
|
||||
static inline void read_seqlock_excl_bh(seqlock_t *sl)
|
||||
{
|
||||
spin_lock_bh(&sl->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* read_sequnlock_excl_bh() - stop a seqlock_t softirq-disabled locking
|
||||
* reader section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*/
|
||||
static inline void read_sequnlock_excl_bh(seqlock_t *sl)
|
||||
{
|
||||
spin_unlock_bh(&sl->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* read_seqlock_excl_irq() - start a non-interruptible seqlock_t locking
|
||||
* reader section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*
|
||||
* _irq variant of read_seqlock_excl(). Use this only if the seqlock_t
|
||||
* write side section, *or other read sections*, can be invoked from a
|
||||
* hardirq context.
|
||||
*/
|
||||
static inline void read_seqlock_excl_irq(seqlock_t *sl)
|
||||
{
|
||||
spin_lock_irq(&sl->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* read_sequnlock_excl_irq() - end an interrupts-disabled seqlock_t
|
||||
* locking reader section
|
||||
* @sl: Pointer to seqlock_t
|
||||
*/
|
||||
static inline void read_sequnlock_excl_irq(seqlock_t *sl)
|
||||
{
|
||||
spin_unlock_irq(&sl->lock);
|
||||
|
|
@ -581,9 +767,26 @@ static inline unsigned long __read_seqlock_excl_irqsave(seqlock_t *sl)
|
|||
return flags;
|
||||
}
|
||||
|
||||
/**
|
||||
* read_seqlock_excl_irqsave() - start a non-interruptible seqlock_t
|
||||
* locking reader section
|
||||
* @lock: Pointer to seqlock_t
|
||||
* @flags: Stack-allocated storage for saving caller's local interrupt
|
||||
* state, to be passed to read_sequnlock_excl_irqrestore().
|
||||
*
|
||||
* _irqsave variant of read_seqlock_excl(). Use this only if the seqlock_t
|
||||
* write side section, *or other read sections*, can be invoked from a
|
||||
* hardirq context.
|
||||
*/
|
||||
#define read_seqlock_excl_irqsave(lock, flags) \
|
||||
do { flags = __read_seqlock_excl_irqsave(lock); } while (0)
|
||||
|
||||
/**
|
||||
* read_sequnlock_excl_irqrestore() - end non-interruptible seqlock_t
|
||||
* locking reader section
|
||||
* @sl: Pointer to seqlock_t
|
||||
* @flags: Caller saved interrupt state, from read_seqlock_excl_irqsave()
|
||||
*/
|
||||
static inline void
|
||||
read_sequnlock_excl_irqrestore(seqlock_t *sl, unsigned long flags)
|
||||
{
|
||||
|
|
@ -591,14 +794,35 @@ read_sequnlock_excl_irqrestore(seqlock_t *sl, unsigned long flags)
|
|||
}
|
||||
|
||||
/**
|
||||
* read_seqbegin_or_lock - begin a sequence number check or locking block
|
||||
* @lock: sequence lock
|
||||
* @seq : sequence number to be checked
|
||||
* read_seqbegin_or_lock() - begin a seqlock_t lockless or locking reader
|
||||
* @lock: Pointer to seqlock_t
|
||||
* @seq : Marker and return parameter. If the passed value is even, the
|
||||
* reader will become a *lockless* seqlock_t reader as in read_seqbegin().
|
||||
* If the passed value is odd, the reader will become a *locking* reader
|
||||
* as in read_seqlock_excl(). In the first call to this function, the
|
||||
* caller *must* initialize and pass an even value to @seq; this way, a
|
||||
* lockless read can be optimistically tried first.
|
||||
*
|
||||
* First try it once optimistically without taking the lock. If that fails,
|
||||
* take the lock. The sequence number is also used as a marker for deciding
|
||||
* whether to be a reader (even) or writer (odd).
|
||||
* N.B. seq must be initialized to an even number to begin with.
|
||||
* read_seqbegin_or_lock is an API designed to optimistically try a normal
|
||||
* lockless seqlock_t read section first. If an odd counter is found, the
|
||||
* lockless read trial has failed, and the next read iteration transforms
|
||||
* itself into a full seqlock_t locking reader.
|
||||
*
|
||||
* This is typically used to avoid seqlock_t lockless readers starvation
|
||||
* (too much retry loops) in the case of a sharp spike in write side
|
||||
* activity.
|
||||
*
|
||||
* Context: if the seqlock_t write section, *or other read sections*, can
|
||||
* be invoked from hardirq or softirq contexts, use the _irqsave or _bh
|
||||
* variant of this function instead.
|
||||
*
|
||||
* Check Documentation/locking/seqlock.rst for template example code.
|
||||
*
|
||||
* Return: the encountered sequence counter value, through the @seq
|
||||
* parameter, which is overloaded as a return parameter. This returned
|
||||
* value must be checked with need_seqretry(). If the read section need to
|
||||
* be retried, this returned value must also be passed as the @seq
|
||||
* parameter of the next read_seqbegin_or_lock() iteration.
|
||||
*/
|
||||
static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq)
|
||||
{
|
||||
|
|
@ -608,17 +832,52 @@ static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq)
|
|||
read_seqlock_excl(lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* need_seqretry() - validate seqlock_t "locking or lockless" read section
|
||||
* @lock: Pointer to seqlock_t
|
||||
* @seq: sequence count, from read_seqbegin_or_lock()
|
||||
*
|
||||
* Return: true if a read section retry is required, false otherwise
|
||||
*/
|
||||
static inline int need_seqretry(seqlock_t *lock, int seq)
|
||||
{
|
||||
return !(seq & 1) && read_seqretry(lock, seq);
|
||||
}
|
||||
|
||||
/**
|
||||
* done_seqretry() - end seqlock_t "locking or lockless" reader section
|
||||
* @lock: Pointer to seqlock_t
|
||||
* @seq: count, from read_seqbegin_or_lock()
|
||||
*
|
||||
* done_seqretry finishes the seqlock_t read side critical section started
|
||||
* with read_seqbegin_or_lock() and validated by need_seqretry().
|
||||
*/
|
||||
static inline void done_seqretry(seqlock_t *lock, int seq)
|
||||
{
|
||||
if (seq & 1)
|
||||
read_sequnlock_excl(lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* read_seqbegin_or_lock_irqsave() - begin a seqlock_t lockless reader, or
|
||||
* a non-interruptible locking reader
|
||||
* @lock: Pointer to seqlock_t
|
||||
* @seq: Marker and return parameter. Check read_seqbegin_or_lock().
|
||||
*
|
||||
* This is the _irqsave variant of read_seqbegin_or_lock(). Use it only if
|
||||
* the seqlock_t write section, *or other read sections*, can be invoked
|
||||
* from hardirq context.
|
||||
*
|
||||
* Note: Interrupts will be disabled only for "locking reader" mode.
|
||||
*
|
||||
* Return:
|
||||
*
|
||||
* 1. The saved local interrupts state in case of a locking reader, to
|
||||
* be passed to done_seqretry_irqrestore().
|
||||
*
|
||||
* 2. The encountered sequence counter value, returned through @seq
|
||||
* overloaded as a return parameter. Check read_seqbegin_or_lock().
|
||||
*/
|
||||
static inline unsigned long
|
||||
read_seqbegin_or_lock_irqsave(seqlock_t *lock, int *seq)
|
||||
{
|
||||
|
|
@ -632,6 +891,18 @@ read_seqbegin_or_lock_irqsave(seqlock_t *lock, int *seq)
|
|||
return flags;
|
||||
}
|
||||
|
||||
/**
|
||||
* done_seqretry_irqrestore() - end a seqlock_t lockless reader, or a
|
||||
* non-interruptible locking reader section
|
||||
* @lock: Pointer to seqlock_t
|
||||
* @seq: Count, from read_seqbegin_or_lock_irqsave()
|
||||
* @flags: Caller's saved local interrupt state in case of a locking
|
||||
* reader, also from read_seqbegin_or_lock_irqsave()
|
||||
*
|
||||
* This is the _irqrestore variant of done_seqretry(). The read section
|
||||
* must've been opened with read_seqbegin_or_lock_irqsave(), and validated
|
||||
* by need_seqretry().
|
||||
*/
|
||||
static inline void
|
||||
done_seqretry_irqrestore(seqlock_t *lock, int seq, unsigned long flags)
|
||||
{
|
||||
|
|
|
|||
Загрузка…
Ссылка в новой задаче