Date: Mon, 18 Jan 2010 16:04:56 +0900 (JST) From: Kohji Okuno <okuno.kohji@jp.panasonic.com> To: attilio@freebsd.org Cc: jroberson@jroberson.net, freebsd-current@freebsd.org, okuno.kohji@jp.panasonic.com Subject: Re: Bug about sched_4bsd? Message-ID: <20100118.160456.519459540419521301.okuno.kohji@jp.panasonic.com> In-Reply-To: <20100118.155352.59640143160034670.okuno.kohji@jp.panasonic.com> References: <20100117.152835.119882392487126976.okuno.kohji@jp.panasonic.com> <3bbf2fe11001171858o4568fe38l9b2db54ec9856b50@mail.gmail.com> <20100118.155352.59640143160034670.okuno.kohji@jp.panasonic.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Hello,
I have a question.
The sleeping thread (on turnstile or on sleepque) can set sched_lock
to td_lock, kernel are allowed?
Best regards,
Kohji Okuno.
> Hello,
>
> Thank you, Attilio.
> I checked your patch. I think that your patch is better.
> I tested the patch quickly, and I think it's OK.
> # This probrem does not occur easily :-<
>
>
> What do you think about maybe_resched()?
> I have never experienced about maybe_resched(), but I think that the
> race condition may occur.
>
> <<Back Trace>>
> sched_4bsd.c: maybe_resched()
> sched_4bsd.c: resetpriority_thread()
> sched_4bsd.c: sched_nice() get thread_lock(td)
> kern_resource.c: donice()
> kern_resource.c: setpriority() get PROC_LOCK()
>
> static void
> maybe_resched(struct thread *td)
> {
> THREAD_LOCK_ASSERT(td, MA_OWNED);
> if (td->td_priority < curthread->td_priority)
> curthread->td_flags |= TDF_NEEDRESCHED;
> }
>
> I think, when td->td_lock is not &sched_lock, curthread->td_lock is
> not locked in maybe_resched().
>
> Best regards,
> Kohji Okuno.
>
> From: Attilio Rao <attilio@freebsd.org>
> Subject: Re: Bug about sched_4bsd?
> Date: Mon, 18 Jan 2010 03:58:41 +0100
> Message-ID: <3bbf2fe11001171858o4568fe38l9b2db54ec9856b50@mail.gmail.com>
>
>> 2010/1/17 Kohji Okuno <okuno.kohji@jp.panasonic.com>:
>>> Hello,
>>>
>>> Could you check sched_4bsd.patch, please?
>>
>> I think, instead, that what needs to happen is to have sched_switch()
>> to do a lock handover from sleepq/turnstile spinlock to schedlock.
>> That way, if threads are willing to contest on td_lock they will be
>> still inhibited.
>> I'm not sure if this patch breaks any invariant, if you may test I
>> would appreciate:
>> http://www.freebsd.org/~attilio/sched_4bsd_schedlock.diff
>>
>> Reviews and comments are appreciated.
>> BTW, nice catch.
>>
>> Attilio
>>
>>
>> --
>> Peace can only be achieved by understanding - A. Einstein
>> _______________________________________________
>> freebsd-current@freebsd.org mailing list
>> http://lists.freebsd.org/mailman/listinfo/freebsd-current
>> To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"
>
> _______________________________________________
> freebsd-current@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-current
> To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20100118.160456.519459540419521301.okuno.kohji>