From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Fri, 16 Nov 2012 17:59:58 +0000 (-0800)
Subject: Merge branches 'urgent.2012.10.27a', 'doc.2012.11.16a', 'fixes.2012.11.13a', 'srcu... 
X-Git-Tag: firefly_0821_release~3680^2~1514^2^2~4
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=aac1cda34b84a9411d6b8d18c3658f094c834911;p=firefly-linux-kernel-4.4.55.git

Merge branches 'urgent.2012.10.27a', 'doc.2012.11.16a', 'fixes.2012.11.13a', 'srcu.2012.10.27a', 'stall.2012.11.13a', 'tracing.2012.11.08a' and 'idle.2012.10.24a' into HEAD

urgent.2012.10.27a: Fix for RCU user-mode transition (already in -tip).

doc.2012.11.08a: Documentation updates, most notably codifying the
	memory-barrier guarantees inherent to grace periods.

fixes.2012.11.13a: Miscellaneous fixes.

srcu.2012.10.27a: Allow statically allocated and initialized srcu_struct
	structures (courtesy of Lai Jiangshan).

stall.2012.11.13a: Add more diagnostic information to RCU CPU stall
	warnings, also decrease from 60 seconds to 21 seconds.

hotplug.2012.11.08a: Minor updates to CPU hotplug handling.

tracing.2012.11.08a: Improved debugfs tracing, courtesy of Michael Wang.

idle.2012.10.24a: Updates to RCU idle/adaptive-idle handling, including
	a boot parameter that maps normal grace periods to expedited.

Resolved conflict in kernel/rcutree.c due to side-by-side change.
---

aac1cda34b84a9411d6b8d18c3658f094c834911
diff --cc kernel/rcutree.c
index 74df86bd9204,74df86bd9204,15a2beec320f,74df86bd9204,24b21cba2cc8,8ed9c481db03,effd47a54b36..5ffadcc3bb26
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@@@@@@@ -2308,10 -2308,10 -2352,10 -2308,10 -2340,10 -2305,32 -2314,10 +2387,32 @@@@@@@@ static int synchronize_sched_expedited_
        */
       void synchronize_sched_expedited(void)
       {
----- -	int firstsnap, s, snap, trycount = 0;
+++++ +	long firstsnap, s, snap;
+++++ +	int trycount = 0;
+++++ +	struct rcu_state *rsp = &rcu_sched_state;
++++   
    - -	/* Note that atomic_inc_return() implies full memory barrier. */
    - -	firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
+++++ +	/*
+++++ +	 * If we are in danger of counter wrap, just do synchronize_sched().
+++++ +	 * By allowing sync_sched_expedited_started to advance no more than
+++++ +	 * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring
+++++ +	 * that more than 3.5 billion CPUs would be required to force a
+++++ +	 * counter wrap on a 32-bit system.  Quite a few more CPUs would of
+++++ +	 * course be required on a 64-bit system.
+++++ +	 */
+++++ +	if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start),
+++++ +			 (ulong)atomic_long_read(&rsp->expedited_done) +
+++++ +			 ULONG_MAX / 8)) {
+++++ +		synchronize_sched();
+++++ +		atomic_long_inc(&rsp->expedited_wrap);
+++++ +		return;
+++++ +	}
    + +
----   	/* Note that atomic_inc_return() implies full memory barrier. */
----   	firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
+++++ +	/*
+++++ +	 * Take a ticket.  Note that atomic_inc_return() implies a
+++++ +	 * full memory barrier.
+++++ +	 */
+++++ +	snap = atomic_long_inc_return(&rsp->expedited_start);
+++++ +	firstsnap = snap;
       	get_online_cpus();
       	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
       
@@@@@@@@ -2328,7 -2328,7 -2372,7 -2328,7 -2360,7 -2357,8 -2334,7 +2439,8 @@@@@@@@
       		if (trycount++ < 10) {
       			udelay(trycount * num_online_cpus());
       		} else {
------ 			synchronize_sched();
++++++ 			wait_rcu_gp(call_rcu_sched);
+++++ +			atomic_long_inc(&rsp->expedited_normal);
       			return;
       		}