Messages in this thread | | | Subject | Re: INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected for kmemleak_lock | From | Catalin Marinas <> | Date | Thu, 03 Sep 2009 09:24:39 +0100 |
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On Wed, 2009-09-02 at 21:19 -0400, Eric Paris wrote: > On Wed, 2009-09-02 at 12:44 +0100, Catalin Marinas wrote: > > On Wed, 2009-09-02 at 11:54 +0100, Catalin Marinas wrote: > > > On Tue, 2009-09-01 at 16:55 -0400, Eric Paris wrote: > > > > I wrote a multithreaded inotify syscall pounder intended to create > > > > files, destroy files, create watches, and destroy watches with the > > > > maximum number of races possible. Instead after letting it run a while > > > > I came upon this! And then my system started to crash in all sorts of > > > > fun and glorious ways (kmem_cache_alloc bugs/panics/whatever) > > > > > > > > -Eric > > > > > > > > [ 2235.913737] ====================================================== > > > > [ 2235.914084] [ INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ] > > > > [ 2235.914084] 2.6.31-rc8-next-20090901 #64 > > > > [ 2235.914084] ------------------------------------------------------ > > > > [ 2235.914084] syscall_thrash/2516 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: > > > > [ 2235.914084] (kthread_create_lock){+.+...}, at: [<ffffffff81091543>] kthread_create+0x73/0x180 > > > > [ 2235.914084] > > > > [ 2235.914084] and this task is already holding: > > > > [ 2235.914084] (kmemleak_lock){..----}, at: [<ffffffff81152611>] create_object+0x161/0x2e0 > > > > [ 2235.914084] which would create a new lock dependency: > > > > [ 2235.914084] (kmemleak_lock){..----} -> (kthread_create_lock){+.+...} > > > > > > Are there other messages from kmemleak printed before that? It looks to > > > me like kmemleak got an exceptional situation (not being able to > > > allocate memory or inserting a pointer into the prio search tree) and it > > > disabled itself. When disabling, it starts a clean-up thread and AFAICT > > > that's the only condition when kmemleak_lock -> kthread_create_lock > > > dependency would be created. > > > > > > I'm not sure whether disabling interrupts around kthread_run in > > > kmemleak_cleanup() would solve the problem. Otherwise, maybe the > > > kmemleak clean-up thread should take a different form or just a thread > > > waiting for a clean-up event (it currently acquires a mutex and cannot > > > be used in interrupt context). > > > > It looks like the kthread_create_lock cannot be acquired in interrupt > > context anyway, so the patch below changes this to a workqueue. > > > > > > kmemleak: Do no create the clean-up thread during kmemleak_disable() > > I'm not going to be able to test as it hasn't happened again. I do > remember seeing messages about kmem leaks being found around the time of > the issue. Although I was working the box as hard as I could, so maybe > I accidentally OOM'd it. Wish there were more I could do to test or > confirm!
OK, no problem. Anyway, it found a potential bug in kmemleak, so the patch I posted should fix it (unless anyone spots any issues with the patch).
Thanks.
-- Catalin
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