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Groups > linux.kernel > #1479728
| From | Cheng Chao <chengchao@kedacom.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v2] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE |
| Date | 2016-09-09 10:20 +0200 |
| Message-ID | <sfpct-qw-1@gated-at.bofh.it> (permalink) |
| References | <sfpct-qw-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
For CONFIG_PREEMPT_NONE=y, when sched_exec() needs migration, sched_exec() calls stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg). If the migration_cpu_stop() can not migrate,why do we call stop_one_cpu()? It just makes the task TASK_UNINTERRUPTIBLE, wakes up the stopper thread, executes migration_cpu_stop(), and the stopper thread wakes up the task. But in fact, all above works are almost useless(wasteful),the reason is migration_cpu_stop() can not migrate. why? migration_cpu_stop() needs the task is TASK_ON_RQ_QUEUED before it calls __migrate_task(). This patch keeps the task TASK_RUNNING instead of TASK_UNINTERRUPTIBLE, so the migration_cpu_stop() can do useful works. Signed-off-by: Cheng Chao <chengchao@kedacom.com> --- kernel/stop_machine.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 4a1ca5f..41aea5e 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -126,6 +126,17 @@ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) cpu_stop_init_done(&done, 1); if (!cpu_stop_queue_work(cpu, &work)) return -ENOENT; + +#if defined(CONFIG_PREEMPT_NONE) + /* + * Makes the stopper thread run as soon as possible. + * And if the caller is TASK_RUNNING, keeps the caller TASK_RUNNING. + * It's special useful for some callers which are expected to be + * TASK_ON_RQ_QUEUED. + * sched_exec does benefit from this improvement. + */ + schedule(); +#endif wait_for_completion(&done.completion); return done.ret; } -- 2.4.11
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[PATCH v2] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao <chengchao@kedacom.com> - 2016-09-09 10:20 +0200
Re: [PATCH v2] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE chengchao <chengchao@kedacom.com> - 2016-09-09 10:20 +0200
Re: [PATCH v2] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Oleg Nesterov <oleg@redhat.com> - 2016-09-09 15:20 +0200
Re: [PATCH v2] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-09 18:30 +0200
[PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao <cs.os.kernel@gmail.com> - 2016-09-10 11:00 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao <cs.os.kernel@gmail.com> - 2016-09-10 12:00 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-10 18:40 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Oleg Nesterov <oleg@redhat.com> - 2016-09-12 13:10 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao <cs.os.kernel@gmail.com> - 2016-09-13 04:50 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-12 13:40 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-12 13:50 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Oleg Nesterov <oleg@redhat.com> - 2016-09-12 15:10 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-12 17:10 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Oleg Nesterov <oleg@redhat.com> - 2016-09-13 18:20 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-13 18:40 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao <cs.os.kernel@gmail.com> - 2016-09-14 04:10 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-14 10:00 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Oleg Nesterov <oleg@redhat.com> - 2016-09-14 17:50 +0200
[tip:sched/core] sched/core: Optimize __schedule() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2016-09-22 16:10 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Cheng Chao <cs.os.kernel@gmail.com> - 2016-09-13 06:10 +0200
Re: [PATCH v3] stop_machine: Make migration_cpu_stop() does useful works for CONFIG_PREEMPT_NONE Peter Zijlstra <peterz@infradead.org> - 2016-09-13 10:50 +0200
[PATCH v4] stop_machine: Avoid a sleep and wakeup in the stop_one_cpu() Cheng Chao <cs.os.kernel@gmail.com> - 2016-09-14 04:10 +0200
Re: [PATCH v4] stop_machine: Avoid a sleep and wakeup in the stop_one_cpu() Oleg Nesterov <oleg@redhat.com> - 2016-09-14 18:00 +0200
Re: [PATCH v4] stop_machine: Avoid a sleep and wakeup in the stop_one_cpu() Cheng Chao <cs.os.kernel@gmail.com> - 2016-09-18 04:10 +0200
[tip:sched/core] stop_machine: Avoid a sleep and wakeup in stop_one_cpu() tip-bot for Cheng Chao <tipbot@zytor.com> - 2016-09-22 16:10 +0200
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