From e6b80a3b0994ea6c3d876d72464f2debbfcfeb05 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 7 Oct 2011 16:25:18 -0700 Subject: 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 Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Lai Jiangshan Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcupdate.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel/rcupdate.c') diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 92e771d7b44b..2bc4e135ff23 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); -- cgit v1.2.1