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Subject[PATCH] lockdep: fix deadlock in lockdep_trace_alloc -v2
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On Fri, 2009-03-20 at 10:26 +0000, Peter Zijlstra wrote:
> Commit-ID: b0992675bc7a5eca3c6a5eeea5ed680cec09c8e7
> Gitweb: http://git.kernel.org/tip/b0992675bc7a5eca3c6a5eeea5ed680cec09c8e7
> Author: Peter Zijlstra <peterz@infradead.org>
> AuthorDate: Fri, 20 Mar 2009 11:13:20 +0100
> Committer: Ingo Molnar <mingo@elte.hu>
> CommitDate: Fri, 20 Mar 2009 11:23:15 +0100
>
> lockdep: fix deadlock in lockdep_trace_alloc
>
> Heiko reported that we grab the graph lock with irqs enabled.
>
> Fix this by providng 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>
> Cc: Nick Piggin <npiggin@suse.de>
> LKML-Reference: <1237544000.24626.52.camel@twins>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>

The below delta fixes it up proper -- saw that I forgot to update the
subject yesterday for the new iterations.

---
Since we now disabled IRQs, checking for IRQs disabled is a bit
pointless, check for it in the saved flags.

Also, add the missing check_flags() check for completeness.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index a39cb6d..b0f0118 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2258,7 +2258,7 @@ void trace_softirqs_off(unsigned long ip)
debug_atomic_inc(&redundant_softirqs_off);
}

-static void __lockdep_trace_alloc(gfp_t gfp_mask)
+static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
{
struct task_struct *curr = current;

@@ -2277,12 +2277,14 @@ static void __lockdep_trace_alloc(gfp_t gfp_mask)
if (!(gfp_mask & __GFP_FS))
return;

- if (DEBUG_LOCKS_WARN_ON(irqs_disabled()))
+ if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
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;
@@ -2291,8 +2293,9 @@ void lockdep_trace_alloc(gfp_t gfp_mask)
return;

raw_local_irq_save(flags);
+ check_flags(flags);
current->lockdep_recursion = 1;
- __lockdep_trace_alloc(gfp_mask);
+ __lockdep_trace_alloc(gfp_mask, flags);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}



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