From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
paulmck@linux.vnet.ibm.com, linux-rt-users@vger.kernel.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
Clark Williams <williams@redhat.com>
Subject: Re: [PATCH 2/2] timer: really raise softirq if there is irq_work to do
Date: Fri, 31 Jan 2014 20:54:07 +0100 [thread overview]
Message-ID: <20140131195407.GQ5002@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <20140131143441.478f79ee@gandalf.local.home>
On Fri, Jan 31, 2014 at 02:34:41PM -0500, Steven Rostedt wrote:
> On Fri, 31 Jan 2014 20:26:54 +0100
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
>
> > On 01/31/2014 06:57 PM, Steven Rostedt wrote:
> >
> > > In vanilla Linux, irq_work_run() is called from update_process_times()
> > > when it is called from the timer interrupt. In -rt, there's reasons we
> >
> > and in vanilla Linux some architectures (like x86 or sparc to name just
> > a few) overwrite arch_irq_work_raise() which means they provide
> > their "own" interrupt like callback. That means on those architectures
> > irq_work_run() gets invoked twice: once via update_process_times() and
> > via and once the custom interface.
> > So my question to the original inventor of this code: Peter, do we
> > really need that arch specific callback? Wouldn't one be enough? Is it
> > that critical that it can't wait to the next timer tick?
>
> There's flags that determine when the next call should be invoked. The
> irq_work_run() should return immediately if it was already done by the
> arch specific call. The work wont be called twice.
>
> As I have worked on code that uses irq_work() I can say that we want
> the arch specific interrupts. For those architectures that don't have
> it will experience larger latencies for the work required. It's
> basically, a "too bad" for them.
>
> But to answer your question, no we want the immediate response.
Yah, what Steve said. That fallback is really a you suck to have to use
this.
next prev parent reply other threads:[~2014-01-31 19:54 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-31 14:34 [PATCH 1/2] irq_work: allow certain work in hard irq context Sebastian Andrzej Siewior
2014-01-31 14:34 ` [PATCH 2/2] timer: really raise softirq if there is irq_work to do Sebastian Andrzej Siewior
2014-01-31 17:07 ` Steven Rostedt
2014-01-31 17:11 ` Steven Rostedt
2014-01-31 17:42 ` Paul E. McKenney
2014-01-31 17:57 ` Steven Rostedt
2014-01-31 19:03 ` Paul E. McKenney
2014-01-31 19:26 ` Sebastian Andrzej Siewior
2014-01-31 19:34 ` Steven Rostedt
2014-01-31 19:48 ` Sebastian Andrzej Siewior
2014-01-31 19:56 ` Steven Rostedt
2014-01-31 20:05 ` Peter Zijlstra
2014-01-31 20:23 ` Sebastian Andrzej Siewior
2014-01-31 20:29 ` Peter Zijlstra
2014-01-31 19:54 ` Peter Zijlstra [this message]
2014-01-31 19:06 ` Sebastian Andrzej Siewior
2014-02-02 4:22 ` [PATCH 1/2] irq_work: allow certain work in hard irq context Mike Galbraith
2014-02-02 20:10 ` Sebastian Andrzej Siewior
2014-02-03 2:43 ` Mike Galbraith
2014-02-03 4:00 ` Mike Galbraith
2014-02-03 8:31 ` Sebastian Andrzej Siewior
2014-02-03 9:26 ` Mike Galbraith
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=20140131195407.GQ5002@laptop.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=bigeasy@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rt-users@vger.kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=williams@redhat.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).