[tip:sched/core] stop_machine: Change __stop_cpus() to rely on cpu_stop_queue_work()

tip-bot for Oleg Nesterov
2015-11-23T16:23:33Z

Commit-ID: 4aff1ca6970afbf9cd916c34a9c442c8ccba905e
Gitweb: http://git.kernel.org/tip/4aff1ca6970afbf9cd916c34a9c442c8ccba905e
Author: Oleg Nesterov <oleg@redhat.com>
AuthorDate: Sun, 15 Nov 2015 20:33:23 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 23 Nov 2015 09:48:19 +0100

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>
---
kernel/stop_machine.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 68b73c4..ed2019a 100644
--- 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;
}

/**