From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
David Howells <dhowells@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel@vger.kernel.org,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: Problem with WARN_ON in mutex_trylock() and rxrpc
Date: Tue, 10 Dec 2019 22:53:56 +0100 [thread overview]
Message-ID: <20191210215356.GC11457@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20191210203225.2kvykwn35gnethjn@linutronix.de>
On Tue, Dec 10, 2019 at 09:32:25PM +0100, Sebastian Andrzej Siewior wrote:
> On 2019-12-10 20:25:38 [+0100], Peter Zijlstra wrote:
> > AFAICT the only assumption it relies on are:
> >
> > - that the softirq will cleanly preempt a task. That is, the task
> > context must not change under the softirq execution.
> >
> > - that the softirq runs non-preemptible.
> >
> > Now, both these properties are rather fundamental to how our softirqs
> > work. And can, therefore, be relied upon, irrespective of the mutex
> > implementation.
>
> softirq is preemptible on -RT (I think you know that already but just in
> case).
Indeed, but there it also runs in task context and then it all works
naturally. The !preempt thing is required for when it runs on top of a
task; then it functions as a priority ceiling like construct.
prev parent reply other threads:[~2019-12-10 21:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-05 12:02 Problem with WARN_ON in mutex_trylock() and rxrpc David Howells
2019-12-05 13:22 ` Peter Zijlstra
2019-12-06 12:32 ` Peter Zijlstra
2019-12-10 18:33 ` Thomas Gleixner
2019-12-10 19:25 ` Peter Zijlstra
2019-12-10 20:32 ` Sebastian Andrzej Siewior
2019-12-10 21:53 ` Peter Zijlstra [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=20191210215356.GC11457@worktop.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=bigeasy@linutronix.de \
--cc=dave@stgolabs.net \
--cc=dhowells@redhat.com \
--cc=fweisbec@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=tglx@linutronix.de \
/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.