On Fri, Jun 01, 2012 at 09:40:35PM -0700, Hugh Dickins wrote:
> In which case, yes, much better to follow your suggestion, and hold
> the lock (with irqs disabled) for only half the time.
>
> Similarly untested patch below.
Things aren't happy with that patch at all.
=============================================
[ INFO: possible recursive locking detected ]
3.5.0-rc1+ #50 Not tainted
---------------------------------------------
trinity-child1/31784 is trying to acquire lock:
(&(&zone->lock)->rlock){-.-.-.}, at: [<ffffffff81165c5d>] suitable_migration_target.isra.15+0x19d/0x1e0
but task is already holding lock:
(&(&zone->lock)->rlock){-.-.-.}, at: [<ffffffff811661fb>] compaction_alloc+0x21b/0x2f0
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&(&zone->lock)->rlock);
lock(&(&zone->lock)->rlock);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by trinity-child1/31784:
#0: (&mm->mmap_sem){++++++}, at: [<ffffffff8115fc46>] vm_mmap_pgoff+0x66/0xb0
#1: (&(&zone->lock)->rlock){-.-.-.}, at: [<ffffffff811661fb>] compaction_alloc+0x21b/0x2f0
stack backtrace:
Pid: 31784, comm: trinity-child1 Not tainted 3.5.0-rc1+ #50
Call Trace:
[<ffffffff810b6584>] __lock_acquire+0x1584/0x1aa0
[<ffffffff810b19c8>] ? trace_hardirqs_off_caller+0x28/0xc0
[<ffffffff8108cd47>] ? local_clock+0x47/0x60
[<ffffffff810b7162>] lock_acquire+0x92/0x1f0
[<ffffffff81165c5d>] ? suitable_migration_target.isra.15+0x19d/0x1e0
[<ffffffff8164ce05>] ? _raw_spin_lock_irqsave+0x25/0x90
[<ffffffff8164ce32>] _raw_spin_lock_irqsave+0x52/0x90
[<ffffffff81165c5d>] ? suitable_migration_target.isra.15+0x19d/0x1e0
[<ffffffff81165c5d>] suitable_migration_target.isra.15+0x19d/0x1e0
[<ffffffff8116620e>] compaction_alloc+0x22e/0x2f0
[<ffffffff81198547>] migrate_pages+0xc7/0x540
[<ffffffff81165fe0>] ? isolate_freepages_block+0x260/0x260
[<ffffffff81166e86>] compact_zone+0x216/0x480
[<ffffffff810b19c8>] ? trace_hardirqs_off_caller+0x28/0xc0
[<ffffffff811673cd>] compact_zone_order+0x8d/0xd0
[<ffffffff811499e5>] ? get_page_from_freelist+0x565/0x970
[<ffffffff811674d9>] try_to_compact_pages+0xc9/0x140
[<ffffffff81642e01>] __alloc_pages_direct_compact+0xaa/0x1d0
Then a bunch of NMI backtraces, and a hard lockup.
Dave
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