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Date: Mon, 16 Feb 2009 09:13:04 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Nick Piggin <npiggin@...e.de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [locking bug] inotify: inconsistent {RECLAIM_FS-ON-W} ->
{IN-RECLAIM_FS-W} usage.
Nick, Peter,
the new __GFP_NOFS tracking in -tip [cf40bd1: "lockdep: annotate reclaim
context (__GFP_NOFS)"] turned up this new lockdep assert on two (32-bit)
testboxes:
[ 1093.677775]
[ 1093.677781] =================================
[ 1093.680031] [ INFO: inconsistent lock state ]
[ 1093.680031] 2.6.29-rc5-tip-01504-gb49eca1-dirty #1
[ 1093.680031] ---------------------------------
[ 1093.680031] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
[ 1093.680031] kswapd0/308 [HC0[0]:SC0[0]:HE1:SE1] takes:
[ 1093.680031] (&inode->inotify_mutex){+.+.?.}, at: [<c0205942>] inotify_inode_is_dead+0x20/0x80
[ 1093.680031] {RECLAIM_FS-ON-W} state was registered at:
[ 1093.680031] [<c01696b9>] mark_held_locks+0x43/0x5b
[ 1093.680031] [<c016baa4>] lockdep_trace_alloc+0x6c/0x6e
[ 1093.680031] [<c01cf8b0>] kmem_cache_alloc+0x20/0x150
[ 1093.680031] [<c040d0ec>] idr_pre_get+0x27/0x6c
[ 1093.680031] [<c02056e3>] inotify_handle_get_wd+0x25/0xad
[ 1093.680031] [<c0205f43>] inotify_add_watch+0x7a/0x129
[ 1093.680031] [<c020679e>] sys_inotify_add_watch+0x20f/0x250
[ 1093.680031] [<c010389e>] sysenter_do_call+0x12/0x35
[ 1093.680031] [<ffffffff>] 0xffffffff
[ 1093.680031] irq event stamp: 60417
[ 1093.680031] hardirqs last enabled at (60417): [<c018d5f5>] call_rcu+0x53/0x59
[ 1093.680031] hardirqs last disabled at (60416): [<c018d5b9>] call_rcu+0x17/0x59
[ 1093.680031] softirqs last enabled at (59656): [<c0146229>] __do_softirq+0x157/0x16b
[ 1093.680031] softirqs last disabled at (59651): [<c0106293>] do_softirq+0x74/0x15d
[ 1093.680031]
[ 1093.680031] other info that might help us debug this:
[ 1093.680031] 2 locks held by kswapd0/308:
[ 1093.680031] #0: (shrinker_rwsem){++++..}, at: [<c01b0502>] shrink_slab+0x36/0x189
[ 1093.680031] #1: (&type->s_umount_key#4){+++++.}, at: [<c01e6d77>] shrink_dcache_memory+0x110/0x1fb
[ 1093.680031]
[ 1093.680031] stack backtrace:
[ 1093.680031] Pid: 308, comm: kswapd0 Not tainted 2.6.29-rc5-tip-01504-gb49eca1-dirty #1
[ 1093.680031] Call Trace:
[ 1093.680031] [<c016947a>] valid_state+0x12a/0x13d
[ 1093.680031] [<c016954e>] mark_lock+0xc1/0x1e9
[ 1093.680031] [<c016a5b4>] ? check_usage_forwards+0x0/0x3f
[ 1093.680031] [<c016ab74>] __lock_acquire+0x2c6/0xac8
[ 1093.680031] [<c01688d9>] ? register_lock_class+0x17/0x228
[ 1093.680031] [<c016b3d3>] lock_acquire+0x5d/0x7a
[ 1093.680031] [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c08824c4>] __mutex_lock_common+0x3a/0x4cb
[ 1093.680031] [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c08829ed>] mutex_lock_nested+0x2e/0x36
[ 1093.680031] [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c0205942>] inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c01e6672>] dentry_iput+0x90/0xc2
[ 1093.680031] [<c01e67a3>] d_kill+0x21/0x45
[ 1093.680031] [<c01e6a46>] __shrink_dcache_sb+0x27f/0x355
[ 1093.680031] [<c01e6dc5>] shrink_dcache_memory+0x15e/0x1fb
[ 1093.680031] [<c01b05ed>] shrink_slab+0x121/0x189
[ 1093.680031] [<c01b0d12>] kswapd+0x39f/0x561
[ 1093.680031] [<c01ae499>] ? isolate_pages_global+0x0/0x233
[ 1093.680031] [<c0157eae>] ? autoremove_wake_function+0x0/0x43
[ 1093.680031] [<c01b0973>] ? kswapd+0x0/0x561
[ 1093.680031] [<c0157daf>] kthread+0x41/0x82
[ 1093.680031] [<c0157d6e>] ? kthread+0x0/0x82
[ 1093.680031] [<c01043ab>] kernel_thread_helper+0x7/0x10
Looks like a genuine upstream bug to me: inotify_handle_get_wd() does
idr_pre_get() which does a kmem_cache_alloc() without GFP_FS - and is
hence deadlockable under extreme MM pressure.
Something like the patch below should be enough to fix it, right?
Ingo
-------------------------->
>From 3023a3e27b909b3b309edac4bc9beb8103f127fa Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@...e.hu>
Date: Mon, 16 Feb 2009 09:10:32 +0100
Subject: [PATCH] inotify: fix GFP_KERNEL related deadlock
enhanced lockdep coverage of __GFP_NOFS turned up this new
lockdep assert:
[ 1093.677775]
[ 1093.677781] =================================
[ 1093.680031] [ INFO: inconsistent lock state ]
[ 1093.680031] 2.6.29-rc5-tip-01504-gb49eca1-dirty #1
[ 1093.680031] ---------------------------------
[ 1093.680031] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
[ 1093.680031] kswapd0/308 [HC0[0]:SC0[0]:HE1:SE1] takes:
[ 1093.680031] (&inode->inotify_mutex){+.+.?.}, at: [<c0205942>] inotify_inode_is_dead+0x20/0x80
[ 1093.680031] {RECLAIM_FS-ON-W} state was registered at:
[ 1093.680031] [<c01696b9>] mark_held_locks+0x43/0x5b
[ 1093.680031] [<c016baa4>] lockdep_trace_alloc+0x6c/0x6e
[ 1093.680031] [<c01cf8b0>] kmem_cache_alloc+0x20/0x150
[ 1093.680031] [<c040d0ec>] idr_pre_get+0x27/0x6c
[ 1093.680031] [<c02056e3>] inotify_handle_get_wd+0x25/0xad
[ 1093.680031] [<c0205f43>] inotify_add_watch+0x7a/0x129
[ 1093.680031] [<c020679e>] sys_inotify_add_watch+0x20f/0x250
[ 1093.680031] [<c010389e>] sysenter_do_call+0x12/0x35
[ 1093.680031] [<ffffffff>] 0xffffffff
[ 1093.680031] irq event stamp: 60417
[ 1093.680031] hardirqs last enabled at (60417): [<c018d5f5>] call_rcu+0x53/0x59
[ 1093.680031] hardirqs last disabled at (60416): [<c018d5b9>] call_rcu+0x17/0x59
[ 1093.680031] softirqs last enabled at (59656): [<c0146229>] __do_softirq+0x157/0x16b
[ 1093.680031] softirqs last disabled at (59651): [<c0106293>] do_softirq+0x74/0x15d
[ 1093.680031]
[ 1093.680031] other info that might help us debug this:
[ 1093.680031] 2 locks held by kswapd0/308:
[ 1093.680031] #0: (shrinker_rwsem){++++..}, at: [<c01b0502>] shrink_slab+0x36/0x189
[ 1093.680031] #1: (&type->s_umount_key#4){+++++.}, at: [<c01e6d77>] shrink_dcache_memory+0x110/0x1fb
[ 1093.680031]
[ 1093.680031] stack backtrace:
[ 1093.680031] Pid: 308, comm: kswapd0 Not tainted 2.6.29-rc5-tip-01504-gb49eca1-dirty #1
[ 1093.680031] Call Trace:
[ 1093.680031] [<c016947a>] valid_state+0x12a/0x13d
[ 1093.680031] [<c016954e>] mark_lock+0xc1/0x1e9
[ 1093.680031] [<c016a5b4>] ? check_usage_forwards+0x0/0x3f
[ 1093.680031] [<c016ab74>] __lock_acquire+0x2c6/0xac8
[ 1093.680031] [<c01688d9>] ? register_lock_class+0x17/0x228
[ 1093.680031] [<c016b3d3>] lock_acquire+0x5d/0x7a
[ 1093.680031] [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c08824c4>] __mutex_lock_common+0x3a/0x4cb
[ 1093.680031] [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c08829ed>] mutex_lock_nested+0x2e/0x36
[ 1093.680031] [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c0205942>] inotify_inode_is_dead+0x20/0x80
[ 1093.680031] [<c01e6672>] dentry_iput+0x90/0xc2
[ 1093.680031] [<c01e67a3>] d_kill+0x21/0x45
[ 1093.680031] [<c01e6a46>] __shrink_dcache_sb+0x27f/0x355
[ 1093.680031] [<c01e6dc5>] shrink_dcache_memory+0x15e/0x1fb
[ 1093.680031] [<c01b05ed>] shrink_slab+0x121/0x189
[ 1093.680031] [<c01b0d12>] kswapd+0x39f/0x561
[ 1093.680031] [<c01ae499>] ? isolate_pages_global+0x0/0x233
[ 1093.680031] [<c0157eae>] ? autoremove_wake_function+0x0/0x43
[ 1093.680031] [<c01b0973>] ? kswapd+0x0/0x561
[ 1093.680031] [<c0157daf>] kthread+0x41/0x82
[ 1093.680031] [<c0157d6e>] ? kthread+0x0/0x82
[ 1093.680031] [<c01043ab>] kernel_thread_helper+0x7/0x10
inotify_handle_get_wd() does idr_pre_get() which does a
kmem_cache_alloc() without __GFP_FS - and is hence deadlockable under
extreme MM pressure.
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
fs/notify/inotify/inotify.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/fs/notify/inotify/inotify.c b/fs/notify/inotify/inotify.c
index dae3f28..331f2e8 100644
--- a/fs/notify/inotify/inotify.c
+++ b/fs/notify/inotify/inotify.c
@@ -156,7 +156,7 @@ static int inotify_handle_get_wd(struct inotify_handle *ih,
int ret;
do {
- if (unlikely(!idr_pre_get(&ih->idr, GFP_KERNEL)))
+ if (unlikely(!idr_pre_get(&ih->idr, GFP_NOFS)))
return -ENOSPC;
ret = idr_get_new_above(&ih->idr, watch, ih->last_wd+1, &watch->wd);
} while (ret == -EAGAIN);
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