Re: [PATCH] kthread: convert stop_machine into a kthread

From: Serge E. Hallyn
Date: Tue Jun 20 2006 - 20:51:05 EST


Quoting Andrew Morton (akpm@xxxxxxxx):
> "Serge E. Hallyn" <serue@xxxxxxxxxx> wrote:
> >
> > Quoting Andrew Morton (akpm@xxxxxxxx):
> > > On Tue, 20 Jun 2006 03:27:45 -0500
> > > "Serge E. Hallyn" <serue@xxxxxxxxxx> wrote:
> > >
> > > > Ah, like so?
> > >
> > > Nope. kthread_bind() is supposed to be called by the thread creator,
> > > before the thread is started.
> > >
> > > The documentation for kthread_bind() is irritatingly hidden in the header
> > > file.
> >
> > Oh, I see - then it makes more sense that it gets away with being so
> > much simpler than set_cpus_allowed().
> >
> > So here's another attempt. However I'm not sure now whether
> > the first round of synchronization around stopmachine_thread_ack
> > is necessary anymore. If any threads fail, we'll find out from the
> > kthread_create() return value, right?
> >
> > Still I'm not sure about that, so first things first:
> >
> > thanks,
> > -serge
> >
> > From: Serge E. Hallyn <serue@xxxxxxxxxx>
> > Date: Tue, 20 Jun 2006 11:01:08 -0500
> > Subject: [PATCH] kthread: update stop_machine to use kthread_bind
> >
> > Update stop_machine to use the more efficient kthread_bind()
> > before running task in place of set_cpus_allowed() after.
> >
> > Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>
> >
> > ---
> >
> > kernel/stop_machine.c | 7 +++++--
> > 1 files changed, 5 insertions(+), 2 deletions(-)
> >
> > e25a88e3d60f3f139f10cc8cd894d87622033a16
> > diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
> > index 2dd5a48..593d8e4 100644
> > --- a/kernel/stop_machine.c
> > +++ b/kernel/stop_machine.c
> > @@ -86,7 +86,8 @@ static void stopmachine_set_state(enum s
> >
> > static int stop_machine(void)
> > {
> > - int i, ret = 0;
> > + int ret = 0;
> > + unsigned int i;
> > struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
> >
> > /* One high-prio thread per cpu. We'll do this one. */
> > @@ -100,11 +101,13 @@ static int stop_machine(void)
> > struct task_struct *tsk;
> > if (i == raw_smp_processor_id())
> > continue;
> > - tsk = kthread_run(stopmachine, (void *)(long)i, "stopmachine");
> > + tsk = kthread_create(stopmachine, NULL, "stopmachine");
> > if (IS_ERR(tsk)) {
> > ret = PTR_ERR(tsk);
> > break;
> > }
> > + kthread_bind(tsk, i);
> > + wake_up_process(tsk);
> > stopmachine_num_threads++;
> > }
> >
>
> You forgot this rather important bit:

Confounded, the only thing I can figure is I must not have done a
git-format-patch to regenerate the patch before I pasted it.

I see it's all sorted out in -mm, but just for the record here's
the patch I meant to send.

thanks,
-serge