[tip:sched/core] stop_machine: Shift the 'done != NULL' check from cpu_stop_signal_done() to callers

tip-bot for Oleg Nesterov
2015-11-23T16:24:16Z

Commit-ID: dd2e3121e3cb16d03a6e3f2db48f260f046f39c2
Gitweb: http://git.kernel.org/tip/dd2e3121e3cb16d03a6e3f2db48f260f046f39c2
Author: Oleg Nesterov <oleg@redhat.com>
AuthorDate: Sun, 15 Nov 2015 20:33:29 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 23 Nov 2015 09:48:19 +0100

stop_machine: Shift the 'done != NULL' check from cpu_stop_signal_done() to callers

Change cpu_stop_queue_work() and cpu_stopper_thread() to check done != NULL
before cpu_stop_signal_done(done). This makes the code more clean imo, note
that cpu_stopper_thread() has to do this check anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Milos Vyletel <milos@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20151115193329.GA8274@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/stop_machine.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 09eb83f..7ff7ace 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -64,10 +64,8 @@ static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
/* signal completion unless @done is NULL */
static void cpu_stop_signal_done(struct cpu_stop_done *done)
{
- if (done) {
- if (atomic_dec_and_test(&done->nr_todo))
- complete(&done->completion);
- }
+ if (atomic_dec_and_test(&done->nr_todo))
+ complete(&done->completion);
}

static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
@@ -88,7 +86,7 @@ static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
enabled = stopper->enabled;
if (enabled)
__cpu_stop_queue_work(stopper, work);
- else
+ else if (work->done)
cpu_stop_signal_done(work->done);
spin_unlock_irqrestore(&stopper->lock, flags);

@@ -457,12 +455,12 @@ repeat:

/* cpu stop callbacks are not allowed to sleep */
preempt_disable();
-
ret = fn(arg);
- if (ret && done)
- done->ret = ret;
- cpu_stop_signal_done(done);
-
+ if (done) {
+ if (ret)
+ done->ret = ret;
+ cpu_stop_signal_done(done);
+ }
/* restore preemption and check it's still balanced */
preempt_enable();
WARN_ONCE(preempt_count(),