Re: 2.6.20-git15 BUG: soft lockup detected on CPU#0! - timers?

From: Ingo Molnar
Date: Fri Feb 23 2007 - 01:13:38 EST


* Michal Piotrowski <michal.k.k.piotrowski@xxxxxxxxx> wrote:

> Here is more
> hardirqs last enabled at (30787): [<c0104249>] syscall_exit_work+0x11/0x26
> hardirqs last disabled at (30788): [<c0103fc9>] ret_from_exception+0x9/0xc
> softirqs last enabled at (30202): [<c01265df>] __do_softirq+0xe4/0xea
> softirqs last disabled at (30193): [<c0106a75>] do_softirq+0x64/0xd1

could you please try the patch below? This is pretty much the only
condition under which we can silently 'leak' pending softirqs, and
trigger the new warning: if something does cond_resched_softirq() in
non-runnable state. (which is a no-no, but nothing enforced this, so it
could in theory happen.) So the question is, with this patch applied, do
you get these new warnings from sched.c?


Subject: [patch] add warning to cond_resched_softirq()
From: Ingo Molnar <mingo@xxxxxxx>

make sure that cond_resched_softirq() is always called with a runnable
task - so that we do not leave softirq work pending indefinitely.

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
kernel/sched.c | 1 +
1 file changed, 1 insertion(+)

Index: linux/kernel/sched.c
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -4689,6 +4689,7 @@ int __sched cond_resched_softirq(void)

if (need_resched() && system_state == SYSTEM_RUNNING) {
+ WARN_ON(current->state != TASK_RUNNING);
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