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Message-ID: <20151117170523.GA13955@redhat.com>
Date: Tue, 17 Nov 2015 18:05:23 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Milos Vyletel <milos@...hat.com>,
Prarit Bhargava <prarit@...hat.com>, Tejun Heo <tj@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/8] stop_machine: make cpu_stop_queue_work() and
stop_one_cpu_nowait() return bool
On 11/15, Oleg Nesterov wrote:
>
> --- 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);
Peter, sorry!!!
I forgot to update the !CONFIG_SMP version of stop_one_cpu_nowait(). Please
see V2 below.
Or please tell me if I should send the incremental patch:
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -65,7 +65,7 @@ static void stop_one_cpu_nowait_workfn(struct work_struct *work)
preempt_enable();
}
-static inline void stop_one_cpu_nowait(unsigned int cpu,
+static inline bool stop_one_cpu_nowait(unsigned int cpu,
cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf)
{
@@ -74,7 +74,10 @@ static inline void stop_one_cpu_nowait(unsigned int cpu,
work_buf->fn = fn;
work_buf->arg = arg;
schedule_work(&work_buf->work);
+ return true;
}
+
+ return false;
}
-------------------------------------------------------------------------------
>From d5710e2dca493046257f97ed18699eed4c36a880 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@...hat.com>
Date: Sat, 14 Nov 2015 19:37:01 +0100
Subject: [PATCH v2 3/8] stop_machine: make cpu_stop_queue_work() and stop_one_cpu_nowait() return bool
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@...hat.com>
---
include/linux/stop_machine.h | 7 +++++--
kernel/stop_machine.c | 16 ++++++++++++----
2 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 0adedca..9ef42e1 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);
@@ -65,7 +65,7 @@ static void stop_one_cpu_nowait_workfn(struct work_struct *work)
preempt_enable();
}
-static inline void stop_one_cpu_nowait(unsigned int cpu,
+static inline bool stop_one_cpu_nowait(unsigned int cpu,
cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf)
{
@@ -74,7 +74,10 @@ static inline void stop_one_cpu_nowait(unsigned int cpu,
work_buf->fn = fn;
work_buf->arg = arg;
schedule_work(&work_buf->work);
+ return true;
}
+
+ return false;
}
static inline int stop_cpus(const struct cpumask *cpumask,
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
--
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