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From: Muni Sekhar <munisekharrms@gmail.com>
To: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
Cc: kernelnewbies <kernelnewbies@kernelnewbies.org>
Subject: Re: wait_event()\ wait_event_interruptible()\ wait_event_interruptible_timeout() and wake_up()
Date: Tue, 30 Jul 2019 07:29:36 +0530
Message-ID: <CAHhAz+ikK+WknFOY1qUTFU-yCEM1m--nbM3w8Xr_Xj0O-puMDA@mail.gmail.com> (raw)
In-Reply-To: <22208.1564424822@turing-police>

On Mon, Jul 29, 2019 at 11:57 PM Valdis Klētnieks
<valdis.kletnieks@vt.edu> wrote:
>
> On Mon, 29 Jul 2019 22:48:57 +0530, Muni Sekhar said:
> > Let us assume that multiple processes are waiting on wait_event()\
> > wait_event_interruptible()\ wait_event_interruptible_timeout(), which
> > process gets woken up on calling wake_up()??
> >
> > I presume wake_up() picks one process, but is there any algorithm to
> > pick which process?
>
> Hint:  If you have more than one process waiting, and they do the same thing
> (think multiple copies of the same kthread), it probably doesn't matter.
>
> If they do different things and which one gets picked matters for correctness,
> you're doing it wrong and probably need some locking.
>
> If they do different things and the results will be correct no matter which
> order they're picked, but you want one to go first for latency/througput
> considerations, you have a scheduling/priority issue and probably need to fix
> it using the vast plethora of knobs and tools available for that purpose.
What are those tools? Can you give some more details on how to fix
latency/throughput issues using those tools..
>


-- 
Thanks,
Sekhar

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Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-29 17:18 Muni Sekhar
2019-07-29 17:28 ` Greg KH
2019-07-29 18:01 ` Bharath Vedartham
2019-07-29 18:07   ` Muni Sekhar
2019-07-29 18:29     ` Valdis Klētnieks
2019-07-29 18:27 ` Valdis Klētnieks
2019-07-30  1:59   ` Muni Sekhar [this message]
2019-08-06  8:45   ` Muni Sekhar
2019-08-06 11:42     ` Valdis Klētnieks
2019-08-06 12:00       ` Muni Sekhar
2019-08-06 12:26         ` Greg KH

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