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| author | Oleg Nesterov <oleg@redhat.com> | 2015-10-08 16:51:31 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-10-20 10:23:53 +0200 |
| commit | 233e7f267e580fefdeb36628b7efe8bfe056d27c (patch) | |
| tree | 8a7f799358b3190f6165fb42592293b6590751ae /include/linux/stop_machine.h | |
| parent | 6af597de62a365dfec6021b9796aa302044e7cc3 (diff) | |
| download | linux-233e7f267e580fefdeb36628b7efe8bfe056d27c.tar.gz linux-233e7f267e580fefdeb36628b7efe8bfe056d27c.tar.xz | |
stop_machine: Ensure that a queued callback will be called before cpu_stop_park()
cpu_stop_queue_work() checks stopper->enabled before it queues the
work, but ->enabled == T can only guarantee cpu_stop_signal_done()
if we race with cpu_down().
This is not enough for stop_two_cpus() or stop_machine(), they will
deadlock if multi_cpu_stop() won't be called by one of the target
CPU's. stop_machine/stop_cpus are fine, they rely on stop_cpus_mutex.
But stop_two_cpus() has to check cpu_active() to avoid the same race
with hotplug, and this check is very unobvious and probably not even
correct if we race with cpu_up().
Change cpu_down() pass to clear ->enabled before cpu_stopper_thread()
flushes the pending ->works and returns with KTHREAD_SHOULD_PARK set.
Note also that smpboot_thread_call() calls cpu_stop_unpark() which
sets enabled == T at CPU_ONLINE stage, so this CPU can't go away until
cpu_stopper_thread() is called at least once. This all means that if
cpu_stop_queue_work() succeeds, we know that work->fn() will be called.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151008145131.GA18139@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/stop_machine.h')
| -rw-r--r-- | include/linux/stop_machine.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index 414d924318ce..7b76362b381c 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -33,6 +33,7 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, struct cpu_stop_work *work_buf); int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg); int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg); +void stop_machine_park(int cpu); #else /* CONFIG_SMP */ |