From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Tue, 20 Sep 2011 04:51:45 +0000 (+1000)
Subject: Merge remote-tracking branch 'rcu/rcu/next'
X-Git-Tag: next-20110920~19
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=93e7d7829a91d2bc14cfaefd07285cef35bdf551;p=karo-tx-linux.git

Merge remote-tracking branch 'rcu/rcu/next'
---

93e7d7829a91d2bc14cfaefd07285cef35bdf551
diff --cc include/linux/rcupdate.h
index 8f4f881a0ad8,9d40e425d46c..ea9bc708ccef
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@@ -238,8 -313,18 +313,18 @@@ extern int rcu_read_lock_bh_held(void)
   *
   * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
   * and while lockdep is disabled.
+  *
+  * Note that if the CPU is in an extended quiescent state, for example,
+  * if the CPU is in dyntick-idle mode, then rcu_read_lock_held() returns
+  * false even if the CPU did an rcu_read_lock().  The reason for this is
+  * that RCU ignores CPUs that are in extended quiescent states, so such
+  * a CPU is effectively never in an RCU read-side critical section
+  * regardless of what RCU primitives it invokes.  This state of affairs
+  * is required -- RCU would otherwise need to periodically wake up
+  * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle
+  * mode.
   */
 -#ifdef CONFIG_PREEMPT
 +#ifdef CONFIG_PREEMPT_COUNT
  static inline int rcu_read_lock_sched_held(void)
  {
  	int lockdep_opinion = 0;
diff --cc kernel/sched.c
index 5895135f0f6f,313c0f63e29a..941360f57b1b
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@@ -8374,8 -8185,10 +8364,9 @@@ static inline int preempt_count_equals(
  
  void __might_sleep(const char *file, int line, int preempt_offset)
  {
 -#ifdef in_atomic
  	static unsigned long prev_jiffy;	/* ratelimiting */
  
+ 	rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
  	if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
  	    system_state != SYSTEM_RUNNING || oops_in_progress)
  		return;