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Subject[PATCH] lockdep: Fix lock_is_held on recursion
From
Date
Subject: lockdep: Fix lock_is_held on recursion
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon Jun 06 12:32:43 CEST 2011

The main lock_is_held() user is lockdep_assert_held(), avoid false
assertions in lockdep_off() sections by unconditionally reporting the
lock is taken.

[ the reason this is important is a lockdep_assert_held() in ttwu()
which triggers a warning under lockdep_off() as in printk() which
can trigger another wakeup and lock up due to spinlock recursion ]

Reported-and-tested-by: Arne Jansen <lists@die-jansens.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
Index: linux-2.6/kernel/lockdep.c
===================================================================
--- linux-2.6.orig/kernel/lockdep.c
+++ linux-2.6/kernel/lockdep.c
@@ -3426,7 +3426,7 @@ int lock_is_held(struct lockdep_map *loc
int ret = 0;

if (unlikely(current->lockdep_recursion))
- return ret;
+ return 1; /* avoid false negative lockdep_assert_held */

raw_local_irq_save(flags);
check_flags(flags);



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