linux-kernel - [PATCH] lockdep: fix deadlock in lockdep_trace

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Date:	Sat, 21 Mar 2009 13:33:08 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	npiggin@...e.de, mingo@...hat.com, hpa@...or.com,
	linux-kernel@...r.kernel.org, heiko.carstens@...ibm.com,
	tglx@...utronix.de, mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: [PATCH] lockdep:  fix deadlock in lockdep_trace_alloc -v2

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@...radead.org>
> AuthorDate: Fri, 20 Mar 2009 11:13:20 +0100
> Committer:  Ingo Molnar <mingo@...e.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@...ibm.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Nick Piggin <npiggin@...e.de>
> LKML-Reference: <1237544000.24626.52.camel@...ns>
> Signed-off-by: Ingo Molnar <mingo@...e.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@...llo.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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