From: Thomas Gleixner <tglx@linutronix.de>
To: Valdis.Kletnieks@vt.edu
Cc: Steven Rostedt <rostedt@goodmis.org>,
Christoph Lameter <cl@gentwo.org>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write()
Date: Tue, 20 Sep 2011 15:51:32 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.2.02.1109201549520.2723@ionos> (raw)
In-Reply-To: <27409.1316522696@turing-police.cc.vt.edu>
On Tue, 20 Sep 2011, Valdis.Kletnieks@vt.edu wrote:
> On Mon, 19 Sep 2011 23:06:17 EDT, Steven Rostedt said:
>
> > It is really confusing to know which version to use. I'm confused by the
> > this_cpu_*() compared with __this_cpu_*(). I'm guessing that most places
> > should use __this_cpu*(). But really this_cpu() should be the default,
> > and the places that can have it outside of preemption should have
> > another name. Maybe use the raw_this_cpu() or safe_this_cpu(), as there
> > is an irqsafe_this_cpu(). Maybe make a preemptsafe_cpu_*(). There should
> > only be a very few locations that are OK to have preemption enabled when
> > calling the this_cpu() code. Lets have those have the funny names and
> > not be the default "this_cpu_*()".
>
> What's the latency hit on those very few locations if we simply put our
> collective foot down and not support a preemptable version of this_cpu_*()?
> "Yes, you *could* preempt here, but for our collective sanity that's not
> supported"...
Full ack.
> > All this_cpu*() code, except the funny named ones, should make sure
> > preemption is disabled, otherwise give a nasty warning. As that is
> > usually a bug if you are using a per cpu variable and can migrate away.
> > The next reference to that value may be incorrect.
>
> You get a much prettier diffstat if you just nuke the funny named ones. ;)
Along with the maze of completely unused incarnations.
> But of course it's early morning and I'm still caffeine-deficient and probably
> overlooking some crucial use case. ;)
I doubt that.
Thanks,
tglx
next prev parent reply other threads:[~2011-09-20 13:51 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-19 21:20 [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write() Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 1/5] x86: Remove const_udelay() caring about which cpu var it uses Steven Rostedt
2011-09-19 21:51 ` Christoph Lameter
2011-09-19 23:31 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 2/5] mm: Switch mod_state() to __this_cpu_read() Steven Rostedt
2011-09-19 22:02 ` Christoph Lameter
2011-09-19 23:48 ` Steven Rostedt
2011-09-20 14:46 ` Christoph Lameter
2011-09-20 15:16 ` Steven Rostedt
2011-09-20 15:54 ` Christoph Lameter
2011-09-20 16:07 ` Steven Rostedt
2011-09-20 22:19 ` Valdis.Kletnieks
2011-09-20 13:49 ` Thomas Gleixner
2011-09-20 14:01 ` Steven Rostedt
2011-09-20 14:51 ` Christoph Lameter
2011-09-20 15:11 ` Steven Rostedt
2011-09-20 15:59 ` Christoph Lameter
2011-09-20 16:03 ` Steven Rostedt
2011-09-20 16:07 ` Christoph Lameter
2011-09-20 15:27 ` Thomas Gleixner
2011-09-20 16:02 ` Christoph Lameter
2011-09-20 16:51 ` Thomas Gleixner
2011-09-20 17:08 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 3/5] memcg: Disable preemption in memcg_check_events() Steven Rostedt
2011-09-20 14:20 ` Johannes Weiner
2011-09-20 14:24 ` Johannes Weiner
2011-09-20 14:33 ` Steven Rostedt
2011-09-24 0:46 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 4/5] printk: Have wake_up_klogd() use __this_cpu_write() Steven Rostedt
2011-09-19 21:54 ` Christoph Lameter
2011-09-19 23:33 ` Steven Rostedt
2011-09-20 14:54 ` Christoph Lameter
2011-09-20 14:55 ` Peter Zijlstra
2011-09-19 21:20 ` [RFC][PATCH 5/5] percpu: Add preempt checks back into this_cpu_read/write() Steven Rostedt
2011-09-19 21:49 ` [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write() Christoph Lameter
2011-09-20 3:06 ` Steven Rostedt
2011-09-20 12:44 ` Valdis.Kletnieks
2011-09-20 13:51 ` Thomas Gleixner [this message]
2011-09-20 14:58 ` Christoph Lameter
2011-09-20 15:17 ` Steven Rostedt
2011-09-20 14:57 ` Christoph Lameter
2011-09-20 15:19 ` Steven Rostedt
2011-09-20 16:08 ` Christoph Lameter
2011-09-20 16:31 ` Steven Rostedt
2011-09-20 16:56 ` Steven Rostedt
2011-09-20 17:09 ` Peter Zijlstra
2011-09-20 17:15 ` Steven Rostedt
2011-09-20 17:25 ` Mathieu Desnoyers
2011-09-20 18:03 ` Steven Rostedt
2011-09-20 18:12 ` Mathieu Desnoyers
2011-09-20 18:27 ` Steven Rostedt
2011-09-20 18:34 ` Mathieu Desnoyers
2011-09-20 22:32 ` Valdis.Kletnieks
2011-09-20 22:17 ` Valdis.Kletnieks
2011-09-21 1:33 ` Steven Rostedt
2011-09-20 15:46 ` Mathieu Desnoyers
2011-09-20 16:00 ` Steven Rostedt
2011-09-20 16:10 ` Christoph Lameter
2011-09-20 16:50 ` Peter Zijlstra
2011-09-20 18:54 ` Steven Rostedt
2011-09-21 15:16 ` Christoph Lameter
2011-09-21 15:31 ` Steven Rostedt
2011-09-21 15:59 ` Christoph Lameter
2011-09-21 16:12 ` Steven Rostedt
2011-09-21 16:32 ` Thomas Gleixner
2011-09-20 2:20 ` Andi Kleen
2011-09-20 3:12 ` Steven Rostedt
2011-09-20 3:17 ` Steven Rostedt
2011-09-20 8:32 ` Thomas Gleixner
2011-09-20 12:10 ` Steven Rostedt
2011-09-20 15:03 ` Christoph Lameter
2011-09-20 15:07 ` Peter Zijlstra
2011-09-20 16:05 ` Christoph Lameter
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=alpine.LFD.2.02.1109201549520.2723@ionos \
--to=tglx@linutronix.de \
--cc=Valdis.Kletnieks@vt.edu \
--cc=akpm@linux-foundation.org \
--cc=cl@gentwo.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
/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.