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author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2008-07-06 09:23:55 (GMT) |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-07-18 14:07:32 (GMT) |
commit | 3cac97cbb14aed00d83eb33d4613b0fe3aaea863 (patch) | |
tree | ba775ff62be34c2a7c17149516509d6c7d70f4d5 | |
parent | 5b664cb235e97afbf34db9c4d77f08ebd725335e (diff) | |
download | linux-3cac97cbb14aed00d83eb33d4613b0fe3aaea863.tar.xz |
rcu classic: simplify the next pending batch
use a batch number(rcp->pending) instead of a flag(rcp->next_pending)
rcu_start_batch() need to change this flag, so mb()s is needed
for memory-access safe.
but(after this patch applied) rcu_start_batch() do not change
this batch number(rcp->pending), rcp->pending is managed by
__rcu_process_callbacks only, and troublesome mb()s are eliminated.
And codes look simpler and clearer.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Gautham Shenoy <ego@in.ibm.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r-- | include/linux/rcuclassic.h | 2 | ||||
-rw-r--r-- | kernel/rcuclassic.c | 22 |
2 files changed, 9 insertions, 15 deletions
diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h index 8c77490..c847e59 100644 --- a/include/linux/rcuclassic.h +++ b/include/linux/rcuclassic.h @@ -45,7 +45,7 @@ struct rcu_ctrlblk { long cur; /* Current batch number. */ long completed; /* Number of the last completed batch */ - int next_pending; /* Is the next batch already waiting? */ + long pending; /* Number of the last pending batch */ int signaled; diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c index 16eeeaa..03726eb 100644 --- a/kernel/rcuclassic.c +++ b/kernel/rcuclassic.c @@ -60,12 +60,14 @@ EXPORT_SYMBOL_GPL(rcu_lock_map); static struct rcu_ctrlblk rcu_ctrlblk = { .cur = -300, .completed = -300, + .pending = -300, .lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock), .cpumask = CPU_MASK_NONE, }; static struct rcu_ctrlblk rcu_bh_ctrlblk = { .cur = -300, .completed = -300, + .pending = -300, .lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock), .cpumask = CPU_MASK_NONE, }; @@ -276,14 +278,8 @@ static void rcu_do_batch(struct rcu_data *rdp) */ static void rcu_start_batch(struct rcu_ctrlblk *rcp) { - if (rcp->next_pending && + if (rcp->cur != rcp->pending && rcp->completed == rcp->cur) { - rcp->next_pending = 0; - /* - * next_pending == 0 must be visible in - * __rcu_process_callbacks() before it can see new value of cur. - */ - smp_wmb(); rcp->cur++; /* @@ -441,16 +437,14 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, /* determine batch number */ rdp->batch = rcp->cur + 1; - /* see the comment and corresponding wmb() in - * the rcu_start_batch() - */ - smp_rmb(); - if (!rcp->next_pending) { + if (rcu_batch_after(rdp->batch, rcp->pending)) { /* and start it/schedule start if it's a new batch */ spin_lock(&rcp->lock); - rcp->next_pending = 1; - rcu_start_batch(rcp); + if (rcu_batch_after(rdp->batch, rcp->pending)) { + rcp->pending = rdp->batch; + rcu_start_batch(rcp); + } spin_unlock(&rcp->lock); } } |