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rcu: optionally leave lockdep enabled after RCU lockdep splat

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There is no need to disable lockdep after an RCU lockdep splat,
so remove the debug_lockdeps_off() from lockdep_rcu_dereference().
To avoid repeated lockdep splats, use a static variable in the inlined
rcu_dereference_check() and rcu_dereference_protected() macros so that
a given instance splats only once, but so that multiple instances can
be detected per boot.

This is controlled by a new config variable CONFIG_PROVE_RCU_REPEATEDLY,
which is disabled by default.  This provides the normal lockdep behavior
by default, but permits people who want to find multiple RCU-lockdep
splats per boot to easily do so.

Requested-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Tested-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Lai Jiangshan
2010-04-20 16:23:07 +08:00
committed by Paul E. McKenney
parent b57f95a382
commit 2b3fc35f69
3 changed files with 26 additions and 4 deletions
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3
kernel/lockdep.c
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@@ -3801,8 +3801,11 @@ void lockdep_rcu_dereference(const char *file, const int line)
{
struct task_struct *curr = current;
#ifndef CONFIG_PROVE_RCU_REPEATEDLY
if (!debug_locks_off())
return;
#endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
/* Note: the following can be executed concurrently, so be careful. */
printk("\n===================================================\n");
printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
printk( "---------------------------------------------------\n");