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authorRichard Cochran <rcochran@linutronix.de>2016-07-27 11:08:18 +0200
committerIngo Molnar <mingo@kernel.org>2016-07-28 18:56:22 +0200
commit4fae16dffb812f0e0d98a0b2b0856ca48ca63e6c (patch)
treec661ae0eaa75eb0f4af66870bb0c34a5b1c4c273 /kernel
parentleds/trigger/cpu: Move from CPU_STARTING to ONLINE level (diff)
downloadlinux-4fae16dffb812f0e0d98a0b2b0856ca48ca63e6c.tar.xz
linux-4fae16dffb812f0e0d98a0b2b0856ca48ca63e6c.zip
timers/core: Correct callback order during CPU hot plug
On the tear-down path, the dead CPU callback for the timers was misplaced within the 'cpuhp_state' enumeration. There is a hidden dependency between the timers and block multiqueue. The timers callback must happen before the block multiqueue callback otherwise a RCU stall occurs. Move the timers callback to the proper place in the state machine. Reported-and-tested-by: Jon Hunter <jonathanh@nvidia.com> Reported-by: kbuild test robot <lkp@intel.com> Fixes: 24f73b99716a ("timers/core: Convert to hotplug state machine") Signed-off-by: Richard Cochran <rcochran@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: John Stultz <john.stultz@linaro.org> Cc: rt@linutronix.de Cc: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1469610498-25914-1-git-send-email-rcochran@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cpu.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f24f45915b54..341bf80f80bd 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1200,11 +1200,6 @@ static struct cpuhp_step cpuhp_bp_states[] = {
.startup = smpcfd_prepare_cpu,
.teardown = smpcfd_dead_cpu,
},
- [CPUHP_TIMERS_DEAD] = {
- .name = "timers dead",
- .startup = NULL,
- .teardown = timers_dead_cpu,
- },
[CPUHP_RCUTREE_PREP] = {
.name = "RCU-tree prepare",
.startup = rcutree_prepare_cpu,
@@ -1221,6 +1216,16 @@ static struct cpuhp_step cpuhp_bp_states[] = {
.skip_onerr = true,
.cant_stop = true,
},
+ /*
+ * On the tear-down path, timers_dead_cpu() must be invoked
+ * before blk_mq_queue_reinit_notify() from notify_dead(),
+ * otherwise a RCU stall occurs.
+ */
+ [CPUHP_TIMERS_DEAD] = {
+ .name = "timers dead",
+ .startup = NULL,
+ .teardown = timers_dead_cpu,
+ },
/* Kicks the plugged cpu into life */
[CPUHP_BRINGUP_CPU] = {
.name = "cpu:bringup",