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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-01-04 15:09:09 -0800
committerIngo Molnar <mingo@elte.hu>2010-01-13 09:06:05 +0100
commit46a1e34eda805501a8b32f26394faa435149f6d1 (patch)
tree56359434e348fce6ffc8701fb4948dee1cb4c91f /kernel/rcutree.c
parent45f014c52eef022873b19d6a20eb0ec9668f2b09 (diff)
downloadop-kernel-dev-46a1e34eda805501a8b32f26394faa435149f6d1.zip
op-kernel-dev-46a1e34eda805501a8b32f26394faa435149f6d1.tar.gz
rcu: Make force_quiescent_state() start grace period if needed
Grace periods cannot be started while force_quiescent_state() is active. This is OK in that the affected CPUs will try again later, but it does induce needless grace-period delays. This patch causes rcu_start_gp() to record a failed attempt to start a grace period. When force_quiescent_state() prepares to return, it then starts the grace period if there was such a failed attempt. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <12626465501854-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d920285..55e8f6e 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -660,6 +660,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
struct rcu_node *rnp = rcu_get_root(rsp);
if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
+ if (cpu_needs_another_gp(rsp, rdp))
+ rsp->fqs_need_gp = 1;
if (rnp->completed == rsp->completed) {
spin_unlock_irqrestore(&rnp->lock, flags);
return;
@@ -1239,6 +1241,12 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
break;
}
rsp->fqs_active = 0;
+ if (rsp->fqs_need_gp) {
+ spin_unlock(&rsp->fqslock); /* irqs remain disabled */
+ rsp->fqs_need_gp = 0;
+ rcu_start_gp(rsp, flags); /* releases rnp->lock */
+ return;
+ }
spin_unlock(&rnp->lock); /* irqs remain disabled */
unlock_fqs_ret:
spin_unlock_irqrestore(&rsp->fqslock, flags);
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