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| author | Paul E. McKenney <paul.mckenney@linaro.org> | 2012-12-17 14:21:14 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-03-26 08:04:50 -0700 |
| commit | b11cc5760a9c48c870ad286e8a6d8fdb998fa58d (patch) | |
| tree | dbe928742df4835403e9a277042dbcaec516b36b /kernel/rcutree.c | |
| parent | 5e44ce35a6ec1a16522fa2099dda27aefd8a584e (diff) | |
| download | lwn-b11cc5760a9c48c870ad286e8a6d8fdb998fa58d.tar.gz lwn-b11cc5760a9c48c870ad286e8a6d8fdb998fa58d.zip | |
rcu: Accelerate RCU callbacks at grace-period end
Now that callback acceleration is idempotent, it is safe to accelerate
callbacks during grace-period cleanup on any CPUs that the kthread happens
to be running on. This commit therefore propagates the completion
of the grace period to the per-CPU data structures, and also adds an
rcu_advance_cbs() just before the cpu_needs_another_gp() check in order
to reduce false-positive grace periods.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.c')
| -rw-r--r-- | kernel/rcutree.c | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 074cb2d974bf..2015bce749f9 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1396,6 +1396,9 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) rcu_for_each_node_breadth_first(rsp, rnp) { raw_spin_lock_irq(&rnp->lock); rnp->completed = rsp->gpnum; + rdp = this_cpu_ptr(rsp->rda); + if (rnp == rdp->mynode) + __rcu_process_gp_end(rsp, rnp, rdp); nocb += rcu_nocb_gp_cleanup(rsp, rnp); raw_spin_unlock_irq(&rnp->lock); cond_resched(); @@ -1408,6 +1411,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) trace_rcu_grace_period(rsp->name, rsp->completed, "end"); rsp->fqs_state = RCU_GP_IDLE; rdp = this_cpu_ptr(rsp->rda); + rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */ if (cpu_needs_another_gp(rsp, rdp)) rsp->gp_flags = 1; raw_spin_unlock_irq(&rnp->lock); @@ -1497,6 +1501,15 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) struct rcu_data *rdp = this_cpu_ptr(rsp->rda); struct rcu_node *rnp = rcu_get_root(rsp); + /* + * If there is no grace period in progress right now, any + * callbacks we have up to this point will be satisfied by the + * next grace period. Also, advancing the callbacks reduces the + * probability of false positives from cpu_needs_another_gp() + * resulting in pointless grace periods. So, advance callbacks! + */ + rcu_advance_cbs(rsp, rnp, rdp); + if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { /* @@ -1509,14 +1522,6 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) return; } - /* - * Because there is no grace period in progress right now, - * any callbacks we have up to this point will be satisfied - * by the next grace period. So this is a good place to - * assign a grace period number to recently posted callbacks. - */ - rcu_accelerate_cbs(rsp, rnp, rdp); - rsp->gp_flags = RCU_GP_FLAG_INIT; raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */ |