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authorFrederic Weisbecker <fweisbec@gmail.com>2011-10-07 16:25:18 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-12-11 10:31:30 -0800
commite6b80a3b0994ea6c3d876d72464f2debbfcfeb05 (patch)
tree207337c207fecf2e05e52ffb3003831d240529fd /kernel/rcupdate.c
parenta0f8eefb127f5be07628954f310a7fc8c82b2fc3 (diff)
downloadvexpress-lsk-e6b80a3b0994ea6c3d876d72464f2debbfcfeb05.tar.gz
rcu: Detect illegal rcu dereference in extended quiescent state
Report that none of the rcu read lock maps are held while in an RCU extended quiescent state (the section between rcu_idle_enter() and rcu_idle_exit()). This helps detect any use of rcu_dereference() and friends from within the section in idle where RCU is not allowed. This way we can guarantee an extended quiescent window where the CPU can be put in dyntick idle mode or can simply aoid to be part of any global grace period completion while in the idle loop. Uses of RCU from such mode are totally ignored by RCU, hence the importance of these checks. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcupdate.c')
-rw-r--r--kernel/rcupdate.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 92e771d7b44..2bc4e135ff2 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -93,6 +93,8 @@ int rcu_read_lock_bh_held(void)
{
if (!debug_lockdep_rcu_enabled())
return 1;
+ if (rcu_is_cpu_idle())
+ return 0;
return in_softirq() || irqs_disabled();
}
EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);