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srcu: Add grace-period sequence numbers

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This commit adds grace-period sequence numbers, which will be used to
handle mid-boot grace periods and per-CPU callback lists.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-03-11 07:14:06 -08:00
parent c2a8ec0778
commit ac367c1c62
2 changed files with 24 additions and 4 deletions
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1
include/linux/srcu.h
View file

@ -46,6 +46,7 @@ struct rcu_batch {
struct srcu_struct {
unsigned long completed;
unsigned long srcu_gp_seq;
struct srcu_array __percpu *per_cpu_ref;
spinlock_t queue_lock; /* protect ->batch_queue, ->running */
int srcu_state;

27
kernel/rcu/srcu.c
View file

@ -110,6 +110,7 @@ static inline void rcu_batch_move(struct rcu_batch *to, struct rcu_batch *from)
static int init_srcu_struct_fields(struct srcu_struct *sp)
{
sp->completed = 0;
sp->srcu_gp_seq = 0;
spin_lock_init(&sp->queue_lock);
sp->srcu_state = SRCU_STATE_IDLE;
rcu_batch_init(&sp->batch_queue);
@ -318,6 +319,15 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
#define SYNCHRONIZE_SRCU_TRYCOUNT 2
#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT 12
/*
* Start an SRCU grace period.
*/
static void srcu_gp_start(struct srcu_struct *sp)
{
WRITE_ONCE(sp->srcu_state, SRCU_STATE_SCAN1);
rcu_seq_start(&sp->srcu_gp_seq);
}
/*
* @@@ Wait until all pre-existing readers complete. Such readers
* will have used the index specified by "idx".
@ -354,6 +364,15 @@ static void srcu_flip(struct srcu_struct *sp)
smp_mb(); /* D */ /* Pairs with C. */
}
/*
* End an SRCU grace period.
*/
static void srcu_gp_end(struct srcu_struct *sp)
{
rcu_seq_end(&sp->srcu_gp_seq);
WRITE_ONCE(sp->srcu_state, SRCU_STATE_DONE);
}
/*
* Enqueue an SRCU callback on the specified srcu_struct structure,
* initiating grace-period processing if it is not already running.
@ -392,7 +411,7 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
smp_mb__after_unlock_lock(); /* Caller's prior accesses before GP. */
rcu_batch_queue(&sp->batch_queue, head);
if (READ_ONCE(sp->srcu_state) == SRCU_STATE_IDLE) {
WRITE_ONCE(sp->srcu_state, SRCU_STATE_SCAN1);
srcu_gp_start(sp);
queue_delayed_work(system_power_efficient_wq, &sp->work, 0);
}
spin_unlock_irqrestore(&sp->queue_lock, flags);
@ -426,7 +445,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
smp_mb__after_unlock_lock(); /* Caller's prior accesses before GP. */
if (READ_ONCE(sp->srcu_state) == SRCU_STATE_IDLE) {
/* steal the processing owner */
WRITE_ONCE(sp->srcu_state, SRCU_STATE_SCAN1);
srcu_gp_start(sp);
rcu_batch_queue(&sp->batch_check0, head);
spin_unlock_irq(&sp->queue_lock);
/* give the processing owner to work_struct */
@ -561,7 +580,7 @@ static void srcu_advance_batches(struct srcu_struct *sp, int trycount)
*/
if (sp->srcu_state == SRCU_STATE_DONE)
WRITE_ONCE(sp->srcu_state, SRCU_STATE_SCAN1);
srcu_gp_start(sp);
if (sp->srcu_state == SRCU_STATE_SCAN1) {
idx = 1 ^ (sp->completed & 1);
@ -608,7 +627,7 @@ static void srcu_advance_batches(struct srcu_struct *sp, int trycount)
*/
rcu_batch_move(&sp->batch_done, &sp->batch_check1);
WRITE_ONCE(sp->srcu_state, SRCU_STATE_DONE);
srcu_gp_end(sp);
}
}