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| author | Nikolay Borisov <kernel@kyup.com> | 2016-10-11 13:55:05 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-11 15:06:33 -0700 |
| commit | 2a1613a586de91457fa93c3e468a6e2438fe52a0 (patch) | |
| tree | 24fb125c15ebf579013d5d0df892d6472d42a1ec /ipc/sem.c | |
| parent | ed27f9122c541a1720898739ac55f824f820b7ff (diff) | |
| download | linux-2a1613a586de91457fa93c3e468a6e2438fe52a0.tar.gz linux-2a1613a586de91457fa93c3e468a6e2438fe52a0.tar.bz2 linux-2a1613a586de91457fa93c3e468a6e2438fe52a0.zip | |
ipc/sem.c: add cond_resched in exit_sme
In CONFIG_PREEMPT=n kernel a softlockup was observed while the for loop in
exit_sem. Apparently it's possible for the loop to take quite a long time
and it doesn't have a scheduling point in it. Since the codes is
executing under an rcu read section this may also cause rcu stalls, which
in turn block synchronize_rcu operations, which more or less de-stabilises
the whole system.
Fix this by introducing a cond_resched() at the beginning of the loop.
So this patch fixes the following:
NMI watchdog: BUG: soft lockup - CPU#10 stuck for 23s! [httpd:18119]
CPU: 10 PID: 18119 Comm: httpd Tainted: G O 4.4.20-clouder2 #6
Hardware name: Supermicro X10DRi/X10DRi, BIOS 1.1 04/14/2015
task: ffff88348d695280 ti: ffff881c95550000 task.ti: ffff881c95550000
RIP: 0010:[<ffffffff81614bc7>] [<ffffffff81614bc7>] _raw_spin_lock+0x17/0x30
RSP: 0018:ffff881c95553e40 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff883161b1eea8 RCX: 000000000000000d
RDX: 0000000000000001 RSI: 000000000000000e RDI: ffff883161b1eea4
RBP: ffff881c95553ea0 R08: ffff881c95553e68 R09: ffff883fef376f88
R10: ffff881fffb58c20 R11: ffffea0072556600 R12: ffff883161b1eea0
R13: ffff88348d695280 R14: ffff883dec427000 R15: ffff8831621672a0
FS: 0000000000000000(0000) GS:ffff881fffb40000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3b3723e020 CR3: 0000000001c0a000 CR4: 00000000001406e0
Call Trace:
? exit_sem+0x7c/0x280
do_exit+0x338/0xb40
do_group_exit+0x43/0xd0
SyS_exit_group+0x14/0x20
entry_SYSCALL_64_fastpath+0x16/0x6e
Link: http://lkml.kernel.org/r/1475154992-6363-1-git-send-email-kernel@kyup.com
Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Cc: Herton R. Krzesinski <herton@redhat.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index 5e318c5f749d..10b94bc59d4a 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -2105,6 +2105,8 @@ void exit_sem(struct task_struct *tsk) struct list_head tasks; int semid, i; + cond_resched(); + rcu_read_lock(); un = list_entry_rcu(ulp->list_proc.next, struct sem_undo, list_proc); |