From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Michael Schanne <michael.schanne@gmail.com>
Cc: linux-rt-users@vger.kernel.org
Subject: Re: liveloock using PREEMPT_RT with i915 driver
Date: Fri, 20 Jun 2025 10:16:52 +0200 [thread overview]
Message-ID: <20250620081652.gUUPOkOh@linutronix.de> (raw)
In-Reply-To: <CAC_kJhTQ635vwtj6c7UpvM3BwNb+baMASbeo8t2zT5m5UfEYHw@mail.gmail.com>
On 2025-06-19 07:19:23 [-0400], Michael Schanne wrote:
> > So you are not using clock_nanosleep() but something like a POSIX timer?
>
> No, I was using timerfd_create() and then calling read() in a loop in
> my timer thread. Is it recommended to use clock_nanosleep() instead?
clock_nanosleep() based delays allow a "direct" wakeup. So yes.
Because of how it is implemented, timerfd based wakeup need to be
performed by a thread which is ktimersd. If you busy-poll the timer from
your application then ktimersd needs to have a higher priority than your
application so that it can preempt it.
ktimersd is also responsible the wakeups of non-RT applications. So if
multiple SCHED_OTHER applications ask for a wakeup then this wake up
will preempt your realtime task.
> -Mike
Sebastian
prev parent reply other threads:[~2025-06-20 8:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-16 2:06 liveloock using PREEMPT_RT with i915 driver Michael Schanne
2025-06-17 10:05 ` Sebastian Andrzej Siewior
[not found] ` <CAC_kJhQZpZoUjavRsSVHuXL5k3-3u6+wdL9=h8Pbv3qWvzeOiw@mail.gmail.com>
2025-06-18 12:16 ` Sebastian Andrzej Siewior
2025-06-19 11:19 ` Michael Schanne
2025-06-20 8:16 ` Sebastian Andrzej Siewior [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250620081652.gUUPOkOh@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=linux-rt-users@vger.kernel.org \
--cc=michael.schanne@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.