diff options
author | Oleg Nesterov | 2015-10-08 19:01:41 +0200 |
---|---|---|
committer | Ingo Molnar | 2015-10-20 10:23:55 +0200 |
commit | d8bc853582bfd81a9c08ca6922aeb01570080ccc (patch) | |
tree | 20b0dd94f84060559063c561cd0599a565e1a39b /kernel | |
parent | 5caa1c089aebcb83ccd5b79a3b88b0aa58288d05 (diff) |
stop_machine: Change cpu_stop_queue_two_works() to rely on stopper->enabled
Change cpu_stop_queue_two_works() to ensure that both CPU's have
stopper->enabled == T or fail otherwise.
This way stop_two_cpus() no longer needs to check cpu_active() to
avoid the deadlock. This patch doesn't remove these checks, we will
do this later.
Note: we need to take both stopper->lock's at the same time, but this
will also help to remove lglock from stop_machine.c, so I hope this
is fine.
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/20151008170141.GA25537@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/stop_machine.c | 29 |
1 files changed, 20 insertions, 9 deletions
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 688d6b37bb59..91fbb109de6c 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -219,12 +219,27 @@ static int multi_cpu_stop(void *data) static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, int cpu2, struct cpu_stop_work *work2) { + struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1); + struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2); + int err; + lg_double_lock(&stop_cpus_lock, cpu1, cpu2); - cpu_stop_queue_work(cpu1, work1); - cpu_stop_queue_work(cpu2, work2); + spin_lock_irq(&stopper1->lock); + spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING); + + err = -ENOENT; + if (!stopper1->enabled || !stopper2->enabled) + goto unlock; + + err = 0; + __cpu_stop_queue_work(stopper1, work1); + __cpu_stop_queue_work(stopper2, work2); +unlock: + spin_unlock(&stopper2->lock); + spin_unlock_irq(&stopper1->lock); lg_double_unlock(&stop_cpus_lock, cpu1, cpu2); - return 0; + return err; } /** * stop_two_cpus - stops two cpus @@ -261,12 +276,8 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * set_state(&msdata, MULTI_STOP_PREPARE); /* - * If we observe both CPUs active we know _cpu_down() cannot yet have - * queued its stop_machine works and therefore ours will get executed - * first. Or its not either one of our CPUs that's getting unplugged, - * in which case we don't care. - * - * This relies on the stopper workqueues to be FIFO. + * We do not want to migrate to inactive CPU. FIXME: move this + * into migrate_swap_stop() callback. */ if (!cpu_active(cpu1) || !cpu_active(cpu2)) { preempt_enable(); |