Commit aea4869f authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull core fixes from Ingo Molnar:
 "The tree contains two RCU fixes and a compiler quirk comment fix"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Make rcu_barrier() understand about missing rcuo kthreads
  compiler/gcc4+: Remove inaccurate comment about 'asm goto' miscompiles
  rcu: More on deadlock between CPU hotplug and expedited grace periods
parents 0f4b0676 21ee24bf

include/linux/compiler-gcc4.h

+0 −1
Original line number Diff line number Diff line
@@ -71,7 +71,6 @@ 
 *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670

 *

 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.

 * Fixed in GCC 4.8.2 and later versions.

 *

 * (asm goto is automatically volatile - the naming reflects this.)

 */

include/linux/compiler-gcc5.h

+0 −1
Original line number Diff line number Diff line
@@ -53,7 +53,6 @@ 
 *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670

 *

 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.

 * Fixed in GCC 4.8.2 and later versions.

 *

 * (asm goto is automatically volatile - the naming reflects this.)

 */

include/trace/events/rcu.h

+9 −9
Original line number Diff line number Diff line
@@ -660,18 +660,18 @@ TRACE_EVENT(rcu_torture_read, 
/*

 * Tracepoint for _rcu_barrier() execution.  The string "s" describes

 * the _rcu_barrier phase:

 *	"Begin": rcu_barrier_callback() started.

 *	"Check": rcu_barrier_callback() checking for piggybacking.

 *	"EarlyExit": rcu_barrier_callback() piggybacked, thus early exit.

 *	"Inc1": rcu_barrier_callback() piggyback check counter incremented.

 *	"Offline": rcu_barrier_callback() found offline CPU

 *	"OnlineNoCB": rcu_barrier_callback() found online no-CBs CPU.

 *	"OnlineQ": rcu_barrier_callback() found online CPU with callbacks.

 *	"OnlineNQ": rcu_barrier_callback() found online CPU, no callbacks.

 *	"Begin": _rcu_barrier() started.

 *	"Check": _rcu_barrier() checking for piggybacking.

 *	"EarlyExit": _rcu_barrier() piggybacked, thus early exit.

 *	"Inc1": _rcu_barrier() piggyback check counter incremented.

 *	"OfflineNoCB": _rcu_barrier() found callback on never-online CPU

 *	"OnlineNoCB": _rcu_barrier() found online no-CBs CPU.

 *	"OnlineQ": _rcu_barrier() found online CPU with callbacks.

 *	"OnlineNQ": _rcu_barrier() found online CPU, no callbacks.

 *	"IRQ": An rcu_barrier_callback() callback posted on remote CPU.

 *	"CB": An rcu_barrier_callback() invoked a callback, not the last.

 *	"LastCB": An rcu_barrier_callback() invoked the last callback.

 *	"Inc2": rcu_barrier_callback() piggyback check counter incremented.

 *	"Inc2": _rcu_barrier() piggyback check counter incremented.

 * The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument

 * is the count of remaining callbacks, and "done" is the piggybacking count.

 */

kernel/cpu.c

+13 −1
Original line number Diff line number Diff line
@@ -64,6 +64,8 @@ static struct { 
	 * an ongoing cpu hotplug operation.

	 */

	int refcount;

	/* And allows lockless put_online_cpus(). */

	atomic_t puts_pending;



#ifdef CONFIG_DEBUG_LOCK_ALLOC

	struct lockdep_map dep_map;
@@ -113,7 +115,11 @@ void put_online_cpus(void) 
{

	if (cpu_hotplug.active_writer == current)

		return;

	mutex_lock(&cpu_hotplug.lock);

	if (!mutex_trylock(&cpu_hotplug.lock)) {

		atomic_inc(&cpu_hotplug.puts_pending);

		cpuhp_lock_release();

		return;

	}



	if (WARN_ON(!cpu_hotplug.refcount))

		cpu_hotplug.refcount++; /* try to fix things up */
@@ -155,6 +161,12 @@ void cpu_hotplug_begin(void) 
	cpuhp_lock_acquire();

	for (;;) {

		mutex_lock(&cpu_hotplug.lock);

		if (atomic_read(&cpu_hotplug.puts_pending)) {

			int delta;



			delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);

			cpu_hotplug.refcount -= delta;

		}

		if (likely(!cpu_hotplug.refcount))

			break;

		__set_current_state(TASK_UNINTERRUPTIBLE);

kernel/rcu/tree.c

+10 −5
Original line number Diff line number Diff line
@@ -3299,11 +3299,16 @@ static void _rcu_barrier(struct rcu_state *rsp) 
			continue;

		rdp = per_cpu_ptr(rsp->rda, cpu);

		if (rcu_is_nocb_cpu(cpu)) {

			if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) {

				_rcu_barrier_trace(rsp, "OfflineNoCB", cpu,

						   rsp->n_barrier_done);

			} else {

				_rcu_barrier_trace(rsp, "OnlineNoCB", cpu,

						   rsp->n_barrier_done);

				atomic_inc(&rsp->barrier_cpu_count);

			__call_rcu(&rdp->barrier_head, rcu_barrier_callback,

				   rsp, cpu, 0);

				__call_rcu(&rdp->barrier_head,

					   rcu_barrier_callback, rsp, cpu, 0);

			}

		} else if (ACCESS_ONCE(rdp->qlen)) {

			_rcu_barrier_trace(rsp, "OnlineQ", cpu,

					   rsp->n_barrier_done);