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SubjectRe: [PATCH] lockdep: fix deadlock in lockdep_trace_alloc
On Fri, 20 Mar 2009 11:26:38 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> Heiko pointed out that checking for irqs_disabled() after we disable
> them is quite pointless..
>
> New patch below.
>
> ---
> Subject: lockdep: fix deadlock in lockdep_trace_alloc
> From: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Date: Fri Mar 20 11:24:21 CET 2009
>
> Heiko reported that we grab the graph lock with irqs enabled.
>
> Fix this by providing the same wrapper as all other lockdep entry
> functions have.
>
> Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
> kernel/lockdep.c | 21 +++++++++++++++++++--
> 1 file changed, 19 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/kernel/lockdep.c
> ===================================================================
> --- linux-2.6.orig/kernel/lockdep.c
> +++ linux-2.6/kernel/lockdep.c
> @@ -2258,7 +2258,7 @@ void trace_softirqs_off(unsigned long ip
> debug_atomic_inc(&redundant_softirqs_off);
> }
>
> -void lockdep_trace_alloc(gfp_t gfp_mask)
> +static void __lockdep_trace_alloc(gfp_t gfp_mask)
> {
> struct task_struct *curr = current;
>
> @@ -2277,10 +2277,27 @@ void lockdep_trace_alloc(gfp_t gfp_mask)
> if (!(gfp_mask & __GFP_FS))
> return;
>
> + mark_held_locks(curr, RECLAIM_FS);
> +}
> +
> +static void check_flags(unsigned long flags);
> +
> +void lockdep_trace_alloc(gfp_t gfp_mask)
> +{
> + unsigned long flags;
> +
> + if (unlikely(current->lockdep_recursion))
> + return;
> +
> if (DEBUG_LOCKS_WARN_ON(irqs_disabled()))
> return;
>
> - mark_held_locks(curr, RECLAIM_FS);
> + raw_local_irq_save(flags);
> + check_flags(flags);
> + current->lockdep_recursion = 1;
> + __lockdep_trace_alloc(gfp_mask);
> + current->lockdep_recursion = 0;
> + raw_local_irq_restore(flags);

Hmm... still not working:

------------[ cut here ]------------
Badness at kernel/lockdep.c:2292
Modules linked in:
CPU: 0 Not tainted 2.6.29-rc8-next-20090320-dirty #19
Process swapper (pid: 0, task: 000000000061ddf0, ksp: 0000000000678000)
Krnl PSW : 0400000180000000 000000000007c784 (lockdep_trace_alloc+0xc0/0xf8)
R:0 T:1 IO:0 EX:0 Key:0 M:0 W:0 P:0 AS:0 CC:0 PM:0 EA:3
Krnl GPRS: 0000000000000003 0000000000fe0f18 0000000000000000 000000000000000f
0000000000667800 0000000000000000 0000000000000000 0000000000000000
000000003fe09f00 0000000000000020 000000003fe0fc00 0000000000677910
0000000000000020 0000000000432538 000000000007c76c 0000000000677910
Krnl Code: 000000000007c778: bf2f1000 icm %rr2,15,0(%rr1)
000000000007c77c: a774ffe8 brc 7,7c74c
000000000007c780: a7f40001 brc 15,7c782
>000000000007c784: a7f4ffe4 brc 15,7c74c
000000000007c788: a7c10010 tmll %rr12,16
000000000007c78c: a784ffd4 brc 8,7c734
000000000007c790: e32002e00004 lg %rr2,736
000000000007c796: 91082016 tm 22(%rr2),8
Call Trace:
([<0000000000677928>] init_thread_union+0x3928/0x4000)
[<00000000000aaa48>] __alloc_pages_internal+0x354/0x570
[<00000000000db184>] cache_alloc_refill+0x41c/0x7ac
[<00000000000db7fa>] kmem_cache_alloc+0x11a/0x150
[<00000000001fae3e>] idr_pre_get+0x92/0xcc
[<00000000001faeac>] ida_pre_get+0x34/0xb4
[<00000000000e399a>] set_anon_super+0x3e/0x108
[<00000000000e46a8>] sget+0x3a4/0x47c
[<00000000000e4fe8>] get_sb_single+0x48/0xec
[<0000000000151d4c>] sysfs_get_sb+0x30/0x44
[<00000000000e3764>] vfs_kern_mount+0x68/0xfc
[<00000000000e382c>] kern_mount_data+0x34/0x44
[<000000000068be74>] sysfs_init+0xb4/0xf4
[<000000000068aa82>] mnt_init+0xbe/0x264
[<000000000068a0f0>] vfs_caches_init+0xec/0x1a4
[<0000000000678dd4>] start_kernel+0x4dc/0x6dc
[<0000000000012020>] _ehead+0x20/0x80
INFO: lockdep is turned off.
Last Breaking-Event-Address:
[<000000000007c780>] lockdep_trace_alloc+0xbc/0xf8


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