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| author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2012-02-23 01:06:51 +0400 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2012-04-30 21:48:20 +0400 |
| commit | 4b7a3e9e32114a09c61995048f055615b5d4c26d (patch) | |
| tree | 562ff1829abb99e830b5e3b3719834b059376b03 /kernel/srcu.c | |
| parent | cef50120b61c2af4ce34bc165e19cad66296f93d (diff) | |
| download | linux-4b7a3e9e32114a09c61995048f055615b5d4c26d.tar.xz | |
rcu: Remove fast check path from __synchronize_srcu()
The fastpath in __synchronize_srcu() is designed to handle cases where
there are a large number of concurrent calls for the same srcu_struct
structure. However, the Linux kernel currently does not use SRCU in
this manner, so remove the fastpath checks for simplicity.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/srcu.c')
| -rw-r--r-- | kernel/srcu.c | 25 |
1 files changed, 1 insertions, 24 deletions
diff --git a/kernel/srcu.c b/kernel/srcu.c index 84c9b97dc3d9..17e95bcc901c 100644 --- a/kernel/srcu.c +++ b/kernel/srcu.c @@ -308,7 +308,7 @@ static void flip_idx_and_wait(struct srcu_struct *sp, bool expedited) */ static void __synchronize_srcu(struct srcu_struct *sp, bool expedited) { - int idx; + int idx = 0; rcu_lockdep_assert(!lock_is_held(&sp->dep_map) && !lock_is_held(&rcu_bh_lock_map) && @@ -316,32 +316,9 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool expedited) !lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section"); - smp_mb(); /* Ensure prior action happens before grace period. */ - idx = ACCESS_ONCE(sp->completed); - smp_mb(); /* Access to ->completed before lock acquisition. */ mutex_lock(&sp->mutex); /* - * Check to see if someone else did the work for us while we were - * waiting to acquire the lock. We need -three- 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). If there - * was only two, we are guaranteed to have waited through only one - * full index-flip phase. So we either (1) wait for three or - * (2) supply the additional ones we need. - */ - - if (sp->completed == idx + 2) - idx = 1; - else if (sp->completed == idx + 3) { - mutex_unlock(&sp->mutex); - return; - } else - idx = 0; - - /* * If there were no helpers, then we need to do two flips of * the index. The first flip is required if there are any * outstanding SRCU readers even if there are no new readers |