Messages in this thread | | | Subject | Re: [PATCH] timer: implement lockdep deadlock detection | From | Johannes Berg <> | Date | Tue, 27 Jan 2009 00:03:56 +0100 |
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On Mon, 2009-01-26 at 23:59 +0100, Johannes Berg wrote: > This modifies the timer code in a way to allow lockdep to detect > deadlocks resulting from a lock being taken in the timer function > as well as around the del_timer_sync() call. > > Validated with this module, otherwise bootup was clean.
Not having a proper stack trace in there is a little confusing:
[ 81.547455] [ 81.547457] ======================================================= [ 81.547657] [ INFO: possible circular locking dependency detected ] [ 81.547759] 2.6.29-rc2-wl-11979-gc32422d-dirty #24 [ 81.547857] ------------------------------------------------------- [ 81.547956] rmmod/3857 is trying to acquire lock: [ 81.548055] (&t){-+..}, at: [<ffffffff80252960>] del_timer_sync+0x0/0xa0 [ 81.548303] [ 81.548303] but task is already holding lock: [ 81.548491] (&l){.+..}, at: [<ffffffffa11f9010>] e+0x10/0x30 [test] [ 81.548736] [ 81.548736] which lock already depends on the new lock. [ 81.548737] [ 81.549023] [ 81.549023] the existing dependency chain (in reverse order) is: [ 81.549212] [ 81.549213] -> #1 (&l){.+..}: [ 81.549544] [<ffffffffffffffff>] 0xffffffffffffffff [ 81.549697] [ 81.549697] -> #0 (&t){-+..}: [ 81.550028] [<ffffffff802737b7>] check_prev_add+0x57/0x770 [ 81.550178] [<ffffffff802744d6>] validate_chain+0x606/0x6c0 [ 81.550322] [<ffffffff802749cf>] __lock_acquire+0x43f/0xa10 [ 81.550471] [<ffffffff80275031>] lock_acquire+0x91/0xc0 [ 81.550619] [<ffffffff8025299d>] del_timer_sync+0x3d/0xa0 [ 81.550767] [<ffffffffa11f901c>] e+0x1c/0x30 [test] [ 81.550911] [<ffffffff80281d9b>] sys_delete_module+0x27b/0x2e0 [ 81.551062] [<ffffffff8020bd1b>] system_call_fastpath+0x16/0x1b [ 81.551213] [<ffffffffffffffff>] 0xffffffffffffffff [ 81.551361] [ 81.551361] other info that might help us debug this: [ 81.551362] [ 81.551646] 1 lock held by rmmod/3857: [ 81.551743] #0: (&l){.+..}, at: [<ffffffffa11f9010>] e+0x10/0x30 [test] [ 81.552035] [ 81.552035] stack backtrace: [ 81.552222] Pid: 3857, comm: rmmod Not tainted 2.6.29-rc2-wl-11979-gc32422d-dirty #24 [ 81.552371] Call Trace: [ 81.552469] [<ffffffff80273260>] print_circular_bug_tail+0xe0/0xf0 [ 81.552571] [<ffffffff802737b7>] check_prev_add+0x57/0x770 [ 81.552672] [<ffffffff802744d6>] validate_chain+0x606/0x6c0 [ 81.552773] [<ffffffff802749cf>] __lock_acquire+0x43f/0xa10 [ 81.552876] [<ffffffff8026fb04>] ? get_lock_stats+0x34/0x70 [ 81.552979] [<ffffffff8026fb04>] ? get_lock_stats+0x34/0x70 [ 81.553080] [<ffffffff80275031>] lock_acquire+0x91/0xc0 [ 81.553181] [<ffffffff80252960>] ? del_timer_sync+0x0/0xa0 [ 81.553284] [<ffffffff8025299d>] del_timer_sync+0x3d/0xa0 [ 81.553383] [<ffffffff80252960>] ? del_timer_sync+0x0/0xa0 [ 81.553487] [<ffffffffa11f901c>] e+0x1c/0x30 [test] [ 81.553588] [<ffffffff80281d9b>] sys_delete_module+0x27b/0x2e0 [ 81.553690] [<ffffffff8020c76d>] ? retint_swapgs+0xe/0x13 [ 81.553792] [<ffffffff80272c52>] ? trace_hardirqs_on_caller+0x182/0x1e0 [ 81.553895] [<ffffffff8020bd1b>] system_call_fastpath+0x16/0x1b
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