229 строки
12 KiB
C
229 строки
12 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
|
|
/*
|
|
* RCU segmented callback lists
|
|
*
|
|
* This seemingly RCU-private file must be available to SRCU users
|
|
* because the size of the TREE SRCU srcu_struct structure depends
|
|
* on these definitions.
|
|
*
|
|
* Copyright IBM Corporation, 2017
|
|
*
|
|
* Authors: Paul E. McKenney <paulmck@linux.net.ibm.com>
|
|
*/
|
|
|
|
#ifndef __INCLUDE_LINUX_RCU_SEGCBLIST_H
|
|
#define __INCLUDE_LINUX_RCU_SEGCBLIST_H
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/atomic.h>
|
|
|
|
/* Simple unsegmented callback lists. */
|
|
struct rcu_cblist {
|
|
struct rcu_head *head;
|
|
struct rcu_head **tail;
|
|
long len;
|
|
};
|
|
|
|
#define RCU_CBLIST_INITIALIZER(n) { .head = NULL, .tail = &n.head }
|
|
|
|
/* Complicated segmented callback lists. ;-) */
|
|
|
|
/*
|
|
* Index values for segments in rcu_segcblist structure.
|
|
*
|
|
* The segments are as follows:
|
|
*
|
|
* [head, *tails[RCU_DONE_TAIL]):
|
|
* Callbacks whose grace period has elapsed, and thus can be invoked.
|
|
* [*tails[RCU_DONE_TAIL], *tails[RCU_WAIT_TAIL]):
|
|
* Callbacks waiting for the current GP from the current CPU's viewpoint.
|
|
* [*tails[RCU_WAIT_TAIL], *tails[RCU_NEXT_READY_TAIL]):
|
|
* Callbacks that arrived before the next GP started, again from
|
|
* the current CPU's viewpoint. These can be handled by the next GP.
|
|
* [*tails[RCU_NEXT_READY_TAIL], *tails[RCU_NEXT_TAIL]):
|
|
* Callbacks that might have arrived after the next GP started.
|
|
* There is some uncertainty as to when a given GP starts and
|
|
* ends, but a CPU knows the exact times if it is the one starting
|
|
* or ending the GP. Other CPUs know that the previous GP ends
|
|
* before the next one starts.
|
|
*
|
|
* Note that RCU_WAIT_TAIL cannot be empty unless RCU_NEXT_READY_TAIL is also
|
|
* empty.
|
|
*
|
|
* The ->gp_seq[] array contains the grace-period number at which the
|
|
* corresponding segment of callbacks will be ready to invoke. A given
|
|
* element of this array is meaningful only when the corresponding segment
|
|
* is non-empty, and it is never valid for RCU_DONE_TAIL (whose callbacks
|
|
* are already ready to invoke) or for RCU_NEXT_TAIL (whose callbacks have
|
|
* not yet been assigned a grace-period number).
|
|
*/
|
|
#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
|
|
#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
|
|
#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
|
|
#define RCU_NEXT_TAIL 3
|
|
#define RCU_CBLIST_NSEGS 4
|
|
|
|
|
|
/*
|
|
* ==NOCB Offloading state machine==
|
|
*
|
|
*
|
|
* ----------------------------------------------------------------------------
|
|
* | SEGCBLIST_RCU_CORE |
|
|
* | |
|
|
* | Callbacks processed by rcu_core() from softirqs or local |
|
|
* | rcuc kthread, without holding nocb_lock. |
|
|
* ----------------------------------------------------------------------------
|
|
* |
|
|
* v
|
|
* ----------------------------------------------------------------------------
|
|
* | SEGCBLIST_RCU_CORE | SEGCBLIST_LOCKING | SEGCBLIST_OFFLOADED |
|
|
* | |
|
|
* | Callbacks processed by rcu_core() from softirqs or local |
|
|
* | rcuc kthread, while holding nocb_lock. Waking up CB and GP kthreads, |
|
|
* | allowing nocb_timer to be armed. |
|
|
* ----------------------------------------------------------------------------
|
|
* |
|
|
* v
|
|
* -----------------------------------
|
|
* | |
|
|
* v v
|
|
* --------------------------------------- ----------------------------------|
|
|
* | SEGCBLIST_RCU_CORE | | | SEGCBLIST_RCU_CORE | |
|
|
* | SEGCBLIST_LOCKING | | | SEGCBLIST_LOCKING | |
|
|
* | SEGCBLIST_OFFLOADED | | | SEGCBLIST_OFFLOADED | |
|
|
* | SEGCBLIST_KTHREAD_CB | | SEGCBLIST_KTHREAD_GP |
|
|
* | | | |
|
|
* | | | |
|
|
* | CB kthread woke up and | | GP kthread woke up and |
|
|
* | acknowledged SEGCBLIST_OFFLOADED. | | acknowledged SEGCBLIST_OFFLOADED|
|
|
* | Processes callbacks concurrently | | |
|
|
* | with rcu_core(), holding | | |
|
|
* | nocb_lock. | | |
|
|
* --------------------------------------- -----------------------------------
|
|
* | |
|
|
* -----------------------------------
|
|
* |
|
|
* v
|
|
* |--------------------------------------------------------------------------|
|
|
* | SEGCBLIST_LOCKING | |
|
|
* | SEGCBLIST_OFFLOADED | |
|
|
* | SEGCBLIST_KTHREAD_GP | |
|
|
* | SEGCBLIST_KTHREAD_CB |
|
|
* | |
|
|
* | Kthreads handle callbacks holding nocb_lock, local rcu_core() stops |
|
|
* | handling callbacks. Enable bypass queueing. |
|
|
* ----------------------------------------------------------------------------
|
|
*/
|
|
|
|
|
|
|
|
/*
|
|
* ==NOCB De-Offloading state machine==
|
|
*
|
|
*
|
|
* |--------------------------------------------------------------------------|
|
|
* | SEGCBLIST_LOCKING | |
|
|
* | SEGCBLIST_OFFLOADED | |
|
|
* | SEGCBLIST_KTHREAD_CB | |
|
|
* | SEGCBLIST_KTHREAD_GP |
|
|
* | |
|
|
* | CB/GP kthreads handle callbacks holding nocb_lock, local rcu_core() |
|
|
* | ignores callbacks. Bypass enqueue is enabled. |
|
|
* ----------------------------------------------------------------------------
|
|
* |
|
|
* v
|
|
* |--------------------------------------------------------------------------|
|
|
* | SEGCBLIST_RCU_CORE | |
|
|
* | SEGCBLIST_LOCKING | |
|
|
* | SEGCBLIST_OFFLOADED | |
|
|
* | SEGCBLIST_KTHREAD_CB | |
|
|
* | SEGCBLIST_KTHREAD_GP |
|
|
* | |
|
|
* | CB/GP kthreads handle callbacks holding nocb_lock, local rcu_core() |
|
|
* | handles callbacks concurrently. Bypass enqueue is enabled. |
|
|
* | Invoke RCU core so we make sure not to preempt it in the middle with |
|
|
* | leaving some urgent work unattended within a jiffy. |
|
|
* ----------------------------------------------------------------------------
|
|
* |
|
|
* v
|
|
* |--------------------------------------------------------------------------|
|
|
* | SEGCBLIST_RCU_CORE | |
|
|
* | SEGCBLIST_LOCKING | |
|
|
* | SEGCBLIST_KTHREAD_CB | |
|
|
* | SEGCBLIST_KTHREAD_GP |
|
|
* | |
|
|
* | CB/GP kthreads and local rcu_core() handle callbacks concurrently |
|
|
* | holding nocb_lock. Wake up CB and GP kthreads if necessary. Disable |
|
|
* | bypass enqueue. |
|
|
* ----------------------------------------------------------------------------
|
|
* |
|
|
* v
|
|
* -----------------------------------
|
|
* | |
|
|
* v v
|
|
* ---------------------------------------------------------------------------|
|
|
* | | |
|
|
* | SEGCBLIST_RCU_CORE | | SEGCBLIST_RCU_CORE | |
|
|
* | SEGCBLIST_LOCKING | | SEGCBLIST_LOCKING | |
|
|
* | SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP |
|
|
* | | |
|
|
* | GP kthread woke up and | CB kthread woke up and |
|
|
* | acknowledged the fact that | acknowledged the fact that |
|
|
* | SEGCBLIST_OFFLOADED got cleared. | SEGCBLIST_OFFLOADED got cleared. |
|
|
* | | The CB kthread goes to sleep |
|
|
* | The callbacks from the target CPU | until it ever gets re-offloaded. |
|
|
* | will be ignored from the GP kthread | |
|
|
* | loop. | |
|
|
* ----------------------------------------------------------------------------
|
|
* | |
|
|
* -----------------------------------
|
|
* |
|
|
* v
|
|
* ----------------------------------------------------------------------------
|
|
* | SEGCBLIST_RCU_CORE | SEGCBLIST_LOCKING |
|
|
* | |
|
|
* | Callbacks processed by rcu_core() from softirqs or local |
|
|
* | rcuc kthread, while holding nocb_lock. Forbid nocb_timer to be armed. |
|
|
* | Flush pending nocb_timer. Flush nocb bypass callbacks. |
|
|
* ----------------------------------------------------------------------------
|
|
* |
|
|
* v
|
|
* ----------------------------------------------------------------------------
|
|
* | SEGCBLIST_RCU_CORE |
|
|
* | |
|
|
* | Callbacks processed by rcu_core() from softirqs or local |
|
|
* | rcuc kthread, without holding nocb_lock. |
|
|
* ----------------------------------------------------------------------------
|
|
*/
|
|
#define SEGCBLIST_ENABLED BIT(0)
|
|
#define SEGCBLIST_RCU_CORE BIT(1)
|
|
#define SEGCBLIST_LOCKING BIT(2)
|
|
#define SEGCBLIST_KTHREAD_CB BIT(3)
|
|
#define SEGCBLIST_KTHREAD_GP BIT(4)
|
|
#define SEGCBLIST_OFFLOADED BIT(5)
|
|
|
|
struct rcu_segcblist {
|
|
struct rcu_head *head;
|
|
struct rcu_head **tails[RCU_CBLIST_NSEGS];
|
|
unsigned long gp_seq[RCU_CBLIST_NSEGS];
|
|
#ifdef CONFIG_RCU_NOCB_CPU
|
|
atomic_long_t len;
|
|
#else
|
|
long len;
|
|
#endif
|
|
long seglen[RCU_CBLIST_NSEGS];
|
|
u8 flags;
|
|
};
|
|
|
|
#define RCU_SEGCBLIST_INITIALIZER(n) \
|
|
{ \
|
|
.head = NULL, \
|
|
.tails[RCU_DONE_TAIL] = &n.head, \
|
|
.tails[RCU_WAIT_TAIL] = &n.head, \
|
|
.tails[RCU_NEXT_READY_TAIL] = &n.head, \
|
|
.tails[RCU_NEXT_TAIL] = &n.head, \
|
|
}
|
|
|
|
#endif /* __INCLUDE_LINUX_RCU_SEGCBLIST_H */
|