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SubjectRe: [BUG] local_softirq_pending storm
Date
On Thursday 24 May 2007 00:08:40 Chuck Ebbert wrote:
> Chuck Ebbert wrote:
> > https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=240982
>
> Another; these started to appear after the below patch was merged:
> > Index: linux/kernel/sched.c
> >
> > > ===================================================================
> > > --- linux.orig/kernel/sched.c
> > > +++ linux/kernel/sched.c
> > > @@ -4212,9 +4212,7 @@ 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;
>
> May 23 19:26:26 localhost kernel: BUG: warning at
> kernel/softirq.c:138/local_bh_enable() (Not tainted) May 23 19:26:26
> localhost kernel: [<c042b2ef>] local_bh_enable+0x45/0x92 May 23 19:26:26
> localhost kernel: [<c06036b7>] cond_resched_softirq+0x2c/0x42 May 23
> 19:26:26 localhost kernel: [<c059d5d0>] release_sock+0x54/0xa3 May 23
> 19:26:26 localhost kernel: [<c04373af>] prepare_to_wait+0x24/0x3f May 23
> 19:26:26 localhost kernel: [<c05e267f>] inet_stream_connect+0x116/0x1ff
> May 23 19:26:26 localhost kernel: [<c0437265>]
> autoremove_wake_function+0x0/0x35 May 23 19:26:26 localhost kernel:
> [<c059c339>] sys_connect+0x82/0xad May 23 19:26:26 localhost kernel:
> [<c059d58f>] release_sock+0x13/0xa3 May 23 19:26:26 localhost kernel:
> [<c0604ad5>] _spin_unlock_bh+0x5/0xd May 23 19:26:26 localhost kernel:
> [<c059e714>] sock_setsockopt+0x4a8/0x4b2 May 23 19:26:26 localhost kernel:
> [<c059b6b6>] sock_attach_fd+0x70/0xd2 May 23 19:26:26 localhost kernel:
> [<c04774a0>] get_empty_filp+0xfc/0x170 May 23 19:26:26 localhost kernel:
> [<c059b54f>] sys_setsockopt+0x9b/0xa7 May 23 19:26:26 localhost kernel:
> [<c059cb83>] sys_socketcall+0xac/0x261 May 23 19:26:26 localhost kernel:
> [<c0404f70>] syscall_call+0x7/0xb

strange, while applying the concerned patch first time I was hand editing __
kernel/sched.c __ and stupidly typed _local_bh_enable() instead of
local_bh_enable() and when did a reboot, as soon as I got inside X I was
welcomed with following message in system log.

[ 152.692609] BUG: at kernel/softirq.c:122 _local_bh_enable()
[ 152.692637] [<b040624d>] show_trace_log_lvl+0x1a/0x2f
[ 152.692658] [<b0406801>] show_trace+0x12/0x14
[ 152.692668] [<b0406885>] dump_stack+0x16/0x18
[ 152.692678] [<b0428d66>] _local_bh_enable+0x8b/0xc3
[ 152.692688] [<b059e497>] cond_resched_softirq+0x2b/0x40
[ 152.692700] [<b05797b6>] established_get_first+0x19/0xad
[ 152.692712] [<b057a831>] tcp_seq_next+0x76/0x8c
[ 152.692722] [<b04875ef>] seq_read+0x17b/0x264
[ 152.692733] [<b047102a>] vfs_read+0xad/0x161
[ 152.692745] [<b04714b6>] sys_read+0x3d/0x61
[ 152.692755] [<b04050d4>] syscall_call+0x7/0xb
[ 152.692765] =======================
[ 152.692770] BUG: at kernel/lockdep.c:1937 trace_softirqs_on()
[ 152.692777] [<b040624d>] show_trace_log_lvl+0x1a/0x2f
[ 152.692789] [<b0406801>] show_trace+0x12/0x14
[ 152.692800] [<b0406885>] dump_stack+0x16/0x18
[ 152.692810] [<b043f5a5>] trace_softirqs_on+0x5f/0xa5
[ 152.692822] [<b0428d8e>] _local_bh_enable+0xb3/0xc3
[ 152.692831] [<b059e497>] cond_resched_softirq+0x2b/0x40
[ 152.692842] [<b05797b6>] established_get_first+0x19/0xad
[ 152.692852] [<b057a831>] tcp_seq_next+0x76/0x8c
[ 152.692862] [<b04875ef>] seq_read+0x17b/0x264
[ 152.692870] [<b047102a>] vfs_read+0xad/0x161
[ 152.692879] [<b04714b6>] sys_read+0x3d/0x61
[ 152.692889] [<b04050d4>] syscall_call+0x7/0xb
[ 152.692899] =======================
[ 159.257890] NOHZ: local_softirq_pending 22
[ 159.266009] NOHZ: local_softirq_pending 22
[ 159.273965] NOHZ: local_softirq_pending 22
[ 159.281884] NOHZ: local_softirq_pending 22
[ 160.712828] NOHZ: local_softirq_pending 22
[ 162.609377] NOHZ: local_softirq_pending 22
[ 162.609804] NOHZ: local_softirq_pending 22
[ 162.610054] NOHZ: local_softirq_pending 22
[ 162.610279] NOHZ: local_softirq_pending 22
[ 162.610502] NOHZ: local_softirq_pending 22
After realzing my mistake, I changed it to local_bh_enable() as was in patch
and since then not a single BUG or local_softirq_pending message occurs in
system log, maybe my system waiting for that condition to happen :).


--
Out of many thousands, one may endeavor for perfection, and of
those who have achieved perfection, hardly one knows Me in truth.
-- Gita Sutra Of Mysticism
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