diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2007-05-23 22:58:18 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-24 05:14:15 +0200 |
| commit | 98d8256739f2c6c636fa2da359f5949c739ae839 (patch) | |
| tree | e2f92238779ff3012b47a8dd93d57b86b6949793 | |
| parent | ehci-fsl: fix cache coherency problem on system with large memory (diff) | |
| download | linux-98d8256739f2c6c636fa2da359f5949c739ae839.tar.xz linux-98d8256739f2c6c636fa2da359f5949c739ae839.zip | |
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>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/sched.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 799d23b4e35d..13cdab3b4c48 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4775,9 +4775,7 @@ 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; |