Messages in this thread | | | Date | Thu, 13 Nov 2008 07:10:00 +0100 | From | Manfred Spraul <> | Subject | Re: [PATCH] SYSVIPC - Fix the ipc structures initialization |
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Andrew Morton wrote: > Time is starting to press on this one. Is there something which we can > revert which would fix this bug? > My previous analysis was bogus, let's start from scratch:
1) the initial oops report: http://bugzilla.kernel.org/show_bug.cgi?id=11796#c0
- lockdep is enabled, the oops is somewhere in __lock_acquire - the instruction that oopses is
>>> lock incl 0x138(%r12) R12 is 0x0038004000000000
That could be an debug_atomic_inc() in __lock_acquire. The class pointer in the spinlock_t is not initialized, thus it crashes. Ingo - is that possible?
2) the latest oops was actually a soft lockup:
It starts with: > [ 400.393024] INFO: trying to register non-static key. > [ 400.397005] the code is fine but needs lockdep annotation. > [ 400.397005] turning off the locking correctness validator. > [ 400.397005] Pid: 4207, comm: sysv_test2 Not tainted 2.6.27-ipc_lock #1 > [ 400.397005] Call Trace: > [ 400.397005] [<ffffffff80257055>] static_obj+0x60/0x77 > [ 400.397005] [<ffffffff8025af59>] __lock_acquire+0x1c8/0x779 > [ 400.397005] [<ffffffff8025b59f>] lock_acquire+0x95/0xc2 > [ 400.397005] [<ffffffff802feb07>] ipc_lock+0x62/0x99 > [ 400.397005] [<ffffffff8045117d>] _spin_lock+0x2d/0x5a > [ 400.397005] [<ffffffff802feb07>] ipc_lock+0x62/0x99 > [ 400.397005] [<ffffffff802feb07>] ipc_lock+0x62/0x99 > [ 400.397005] [<ffffffff802feaa5>] ipc_lock+0x0/0x99 > [ 400.397005] [<ffffffff802feb46>] ipc_lock_check+0x8/0x53 > [ 400.397005] [<ffffffff803002c3>] sys_msgctl+0x188/0x461 > [ 400.397005] [<ffffffff80259ac7>] trace_hardirqs_on_caller+0x100/0x12a > [ 400.397005] [<ffffffff80450d49>] trace_hardirqs_on_thunk+0x3a/0x3f > [ 400.397005] [<ffffffff80259ac7>] trace_hardirqs_on_caller+0x100/0x12a > [ 400.397005] [<ffffffff80212e09>] sched_clock+0x5/0x7 > [ 400.397005] [<ffffffff80450d49>] trace_hardirqs_on_thunk+0x3a/0x3f > [ 400.397005] [<ffffffff80213021>] native_sched_clock+0x8c/0xa5 > [ 400.397005] [<ffffffff80212e09>] sched_clock+0x5/0x7 > [ 400.397005] [<ffffffff8020bf7a>] system_call_fastpath+0x16/0x1b > [ 400.397005] > [ 464.933003] BUG: soft lockup - CPU#2 stuck for 61s! [sysv_test2:4207] > [ 464.933006] Call Trace: > [ 464.933006] [<ffffffff8033dc6b>] _raw_spin_lock+0x98/0x100 > [ 464.933006] [<ffffffff8045119e>] _spin_lock+0x4e/0x5a > [ 464.933006] [<ffffffff802feb07>] ipc_lock+0x62/0x99
For me, it reads like an uninitialized spinlock_t: The static_obj test in kernel/lockdep.c notices that something is wrong and disables itself. But then _raw_spin_lock() tries to acquire the uninitialized spinlock and loops forever, because noone does spin_unlock(). after 60 seconds, the soft lockup detection notices the problem and oopses.
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