stop_machine: Change stop_one_cpu() to rely on cpu_stop_queue_work()

Change stop_one_cpu() to return -ENOENT if cpu_stop_queue_work() fails.
Otherwise we know that ->executed must be true after wait_for_completion()
so we can just return done.ret.

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/20151115193320.GA8259@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 0ec1f16..68b73c4 100644 (file)
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -128,9 +128,11 @@ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
        struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };
 
        cpu_stop_init_done(&done, 1);
-       cpu_stop_queue_work(cpu, &work);
+       if (!cpu_stop_queue_work(cpu, &work))
+               return -ENOENT;
        wait_for_completion(&done.completion);
-       return done.executed ? done.ret : -ENOENT;
+       WARN_ON(!done.executed);
+       return done.ret;
 }
 
 /* This controls the threads on each CPU. */