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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-01-04 18:09:09 -0500
committerIngo Molnar <mingo@elte.hu>2010-01-13 03:06:05 -0500
commit46a1e34eda805501a8b32f26394faa435149f6d1 (patch)
tree56359434e348fce6ffc8701fb4948dee1cb4c91f /kernel/rcutree.c
parent45f014c52eef022873b19d6a20eb0ec9668f2b09 (diff)
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 d9202857d3ad..55e8f6ef8195 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -660,6 +660,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
660 struct rcu_node *rnp = rcu_get_root(rsp); 660 struct rcu_node *rnp = rcu_get_root(rsp);
661 661
662 if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { 662 if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
663 if (cpu_needs_another_gp(rsp, rdp))
664 rsp->fqs_need_gp = 1;
663 if (rnp->completed == rsp->completed) { 665 if (rnp->completed == rsp->completed) {
664 spin_unlock_irqrestore(&rnp->lock, flags); 666 spin_unlock_irqrestore(&rnp->lock, flags);
665 return; 667 return;
@@ -1239,6 +1241,12 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
1239 break; 1241 break;
1240 } 1242 }
1241 rsp->fqs_active = 0; 1243 rsp->fqs_active = 0;
1244 if (rsp->fqs_need_gp) {
1245 spin_unlock(&rsp->fqslock); /* irqs remain disabled */
1246 rsp->fqs_need_gp = 0;
1247 rcu_start_gp(rsp, flags); /* releases rnp->lock */
1248 return;
1249 }
1242 spin_unlock(&rnp->lock); /* irqs remain disabled */ 1250 spin_unlock(&rnp->lock); /* irqs remain disabled */
1243unlock_fqs_ret: 1251unlock_fqs_ret:
1244 spin_unlock_irqrestore(&rsp->fqslock, flags); 1252 spin_unlock_irqrestore(&rsp->fqslock, flags);