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authorThomas Gleixner <tglx@linutronix.de>2007-05-22 08:38:50 +0200
committerChris Wright <chrisw@sous-sol.org>2007-06-11 11:36:45 -0700
commitf7b901ae5dbcacf8808c98e5104e56567600918d (patch)
tree0cbff6141c9e8c5da39cbea8f18e78850d9c2ab1
parentaa2112f41c593ea73d7b99ecaa8d4cb60fe37404 (diff)
[PATCH] Prevent going idle with softirq pending
The NOHZ patch contains a check for softirqs pending when a CPU goes idle. The BUG is unrelated to NOHZ, it just was made visible by the NOHZ patch. The BUG showed up mainly on P4 / hyperthreading enabled machines which lead the investigations into the wrong direction in the first place. The real cause is in cond_resched_softirq(): cond_resched_softirq() is enabling softirqs without invoking the softirq daemon when softirqs are pending. This leads to the warning message in the NOHZ idle code: t1 runs softirq disabled code on CPU#0 interrupt happens, softirq is raised, but deferred (softirqs disabled) t1 calls cond_resched_softirq() enables softirqs via _local_bh_enable() calls schedule() t2 runs t1 is migrated to CPU#1 t2 is done and invokes idle() NOHZ detects the pending softirq Fix: change _local_bh_enable() to local_bh_enable() so the softirq daemon is invoked. Thanks to Anant Nitya for debugging this with great patience ! Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Anant Nitya <kernel@prachanda.info> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--kernel/sched.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index b9a683730148..a3993b9e7503 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4545,9 +4545,7 @@ int __sched cond_resched_softirq(void)
BUG_ON(!in_softirq());
if (need_resched() && system_state == SYSTEM_RUNNING) {
- raw_local_irq_disable();
- _local_bh_enable();
- raw_local_irq_enable();
+ local_bh_enable();
__cond_resched();
local_bh_disable();
return 1;