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

Change queue_stop_cpus_work() to return true if it queues at least one
work, this means that the caller should wait.

__stop_cpus() can check the value returned by queue_stop_cpus_work() and
avoid done.executed, just like stop_one_cpu() does.

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/20151115193323.GA8262@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 68b73c40040835cc5a3ab97f876416548800fa67..ed2019ac192dd34c92622850bfed44301f06f899 100644 (file)
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -318,12 +318,13 @@ bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
 /* static data for stop_cpus */
 static DEFINE_MUTEX(stop_cpus_mutex);
 
-static void queue_stop_cpus_work(const struct cpumask *cpumask,
+static bool queue_stop_cpus_work(const struct cpumask *cpumask,
                                 cpu_stop_fn_t fn, void *arg,
                                 struct cpu_stop_done *done)
 {
        struct cpu_stop_work *work;
        unsigned int cpu;
+       bool queued = false;
 
        /*
         * Disable preemption while queueing to avoid getting
@@ -336,9 +337,12 @@ static void queue_stop_cpus_work(const struct cpumask *cpumask,
                work->fn = fn;
                work->arg = arg;
                work->done = done;
-               cpu_stop_queue_work(cpu, work);
+               if (cpu_stop_queue_work(cpu, work))
+                       queued = true;
        }
        lg_global_unlock(&stop_cpus_lock);
+
+       return queued;
 }
 
 static int __stop_cpus(const struct cpumask *cpumask,
@@ -347,9 +351,11 @@ static int __stop_cpus(const struct cpumask *cpumask,
        struct cpu_stop_done done;
 
        cpu_stop_init_done(&done, cpumask_weight(cpumask));
-       queue_stop_cpus_work(cpumask, fn, arg, &done);
+       if (!queue_stop_cpus_work(cpumask, fn, arg, &done))
+               return -ENOENT;
        wait_for_completion(&done.completion);
-       return done.executed ? done.ret : -ENOENT;
+       WARN_ON(!done.executed);
+       return done.ret;
 }
 
 /**