[PATCH 3/8] stop_machine: make cpu_stop_queue_work() and stop_one_cpu_nowait() return bool

Oleg Nesterov
2015-11-15T18:38:41Z

Change cpu_stop_queue_work() to return true if the work was queued and
change stop_one_cpu_nowait() to return the result of cpu_stop_queue_work().
This makes it more useful, for example now you can alloc cpu_stop_work for
stop_one_cpu_nowait() and free it in the callback or if stop_one_cpu_nowait()
fails, currently this is impossible because you can't know if @fn will be
called or not.

Also, this allows to kill cpu_stop_done->executed, see the next changes.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
include/linux/stop_machine.h | 2 +-
kernel/stop_machine.c | 16 ++++++++++++----
2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 0adedca..40b239a 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -29,7 +29,7 @@ struct cpu_stop_work {

int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
-void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf);
int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 17f01a9..0ec1f16 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -81,17 +81,21 @@ static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
}

/* queue @work to @stopper. if offline, @work is completed immediately */
-static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
+static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
{
struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
unsigned long flags;
+ bool enabled;

spin_lock_irqsave(&stopper->lock, flags);
- if (stopper->enabled)
+ enabled = stopper->enabled;
+ if (enabled)
__cpu_stop_queue_work(stopper, work);
else
cpu_stop_signal_done(work->done, false);
spin_unlock_irqrestore(&stopper->lock, flags);
+
+ return enabled;
}

/**
@@ -297,12 +301,16 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
*
* CONTEXT:
* Don't care.
+ *
+ * RETURNS:
+ * true if cpu_stop_work was queued successfully and @fn will be called,
+ * false otherwise.
*/
-void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf)
{
*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
- cpu_stop_queue_work(cpu, work_buf);
+ return cpu_stop_queue_work(cpu, work_buf);
}

/* static data for stop_cpus */
--
1.5.5.1