Messages in this thread | | | Date | Sun, 11 Mar 2007 21:41:43 -0700 | From | "Paul E. McKenney" <> | Subject | Re: 2.6.21-rc3-mm1 |
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On Sun, Mar 11, 2007 at 06:02:31PM +0100, Michal Piotrowski wrote: > On 10/03/07, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > >On Fri, Mar 09, 2007 at 06:18:51PM -0800, Andrew Morton wrote: > >> > On Thu, 08 Mar 2007 21:50:29 +0100 Michal Piotrowski > ><michal.k.k.piotrowski@gmail.com> wrote: > >> > Andrew Morton napisał(a): > >> > > Temporarily at > >> > > > >> > > http://userweb.kernel.org/~akpm/2.6.21-rc3-mm1/ > >> > > > >> > > Will appear later at > >> > > > >> > > > >ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc3/2.6.21-rc3-mm1/ > >> > > > >> > > >> > cpu_hotplug (AutoTest) hangs at this > >> > > >> > ============================================= > >> > [ INFO: possible recursive locking detected ] > >> > 2.6.21-rc3-mm1 #2 > >> > --------------------------------------------- > >> > sh/7213 is trying to acquire lock: > >> > (sched_hotcpu_mutex){--..}, at: [<c033883a>] mutex_lock+0x1c/0x1f > >> > > >> > but task is already holding lock: > >> > (sched_hotcpu_mutex){--..}, at: [<c033883a>] mutex_lock+0x1c/0x1f > >> > > >> > other info that might help us debug this: > >> > 4 locks held by sh/7213: > >> > #0: (cpu_add_remove_lock){--..}, at: [<c033883a>] > >mutex_lock+0x1c/0x1f > >> > #1: (sched_hotcpu_mutex){--..}, at: [<c033883a>] mutex_lock+0x1c/0x1f > >> > #2: (cache_chain_mutex){--..}, at: [<c033883a>] mutex_lock+0x1c/0x1f > >> > #3: (workqueue_mutex){--..}, at: [<c033883a>] mutex_lock+0x1c/0x1f > >> > >> That's pretty useless, isn't it? We need to know the mutex_lock() caller > >> here. > >> > >> > stack backtrace > >> > [<c0105256>] show_trace_log_lvl+0x1a/0x2f > >> > [<c010597b>] show_trace+0x12/0x14 > >> > [<c0105a3d>] dump_stack+0x16/0x18 > >> > [<c013fc73>] __lock_acquire+0x1aa/0xceb > >> > [<c014082d>] lock_acquire+0x79/0x93 > >> > [<c03385dc>] __mutex_lock_slowpath+0x107/0x349 > >> > [<c033883a>] mutex_lock+0x1c/0x1f > >> > [<c011d924>] sched_getaffinity+0x14/0x91 > >> > [<c015796d>] __synchronize_sched+0x11/0x5f > >> > [<c011d257>] detach_destroy_domains+0x2c/0x30 > >> > [<c011fc1a>] update_sched_domains+0x27/0x3a > >> > [<c012fe7a>] notifier_call_chain+0x2b/0x4a > >> > [<c012fec6>] __raw_notifier_call_chain+0x19/0x1e > >> > [<c0145756>] _cpu_down+0x70/0x282 > >> > [<c014598e>] cpu_down+0x26/0x38 > >> > [<c0272714>] store_online+0x27/0x5a > >> > [<c026f610>] sysdev_store+0x20/0x25 > >> > [<c01b7a8e>] sysfs_write_file+0xc1/0xe9 > >> > [<c0180052>] vfs_write+0xd1/0x15a > >> > [<c0180682>] sys_write+0x3d/0x72 > >> > [<c0104270>] syscall_call+0x7/0xb > >> > > >> > l *0xc033883a > >> > 0xc033883a is in mutex_lock > >(/mnt/md0/devel/linux-mm/kernel/mutex.c:92). > >> > 87 /* > >> > 88 * The locking fastpath is the 1->0 transition from > >> > 89 * 'unlocked' into 'locked' state. > >> > 90 */ > >> > 91 __mutex_fastpath_lock(&lock->count, > >__mutex_lock_slowpath); > >> > 92 } > >> > 93 > >> > 94 EXPORT_SYMBOL(mutex_lock); > >> > 95 > >> > 96 static void fastcall noinline __sched > >> > > >> > I didn't test other -mm's with this test. > >> > > >> > > >http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/2.6.21-rc3-mm1/console.log > >> > > >http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/2.6.21-rc3-mm1/mm-config > >> > >> I can't immediately spot the bug. Probably it's caused by rcu-preempt's > >> changes to synchronize_sched(): that function now does a heap more than > >it > >> used to, including taking sched_hotcpu_muex. > >> > >> So, what to do about this. Paul, I'm thinking that I should drop > >> rcu-preempt for now - I don't think we ended up being able to identify > >any > >> particular benefit which it brings to current mainline, and I suspect > >that > >> things will become simpler if/when we start using the process freezer for > >> CPU hotplug. > > > >It certainly makes sense for Michal to try backing out rcu-preempt using > >your broken-out list of patches. If that makes the problem go away, > > Problem is caused by rcu-preempt.patch.
OK, clearly we need to fix this. You might be right about the freezer code having to go in first, Andrew -- will see!
Thanx, Paul
> >then I would certainly have a hard time arguing with you. We are working > >on getting measurements showing benefit of rcu-preempt, but aren't there > >yet.
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