From: Peter Zijlstra <peterz@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Tony Luck <tony.luck@intel.com>, Robert Richter <rric@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Aaro Koskinen <aaro.koskinen@iki.fi>,
David Daney <david.daney@cavium.com>,
linux-kernel@vger.kernel.org
Subject: Re: smp_call_function_single with wait=0 considered harmful
Date: Fri, 28 Feb 2014 13:26:24 +0100 [thread overview]
Message-ID: <20140228122624.GF9987@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20131204164627.GA27677@infradead.org>
On Wed, Dec 04, 2013 at 08:46:27AM -0800, Christoph Hellwig wrote:
> While doing my recent work on the generic smp function calls I noticed
> that smp_call_function_single without the wait flag can't work, as
> it allocates struct call_single_data on stack, and without the wait
> flag will happily return before the IPI has been executed.
It doesn't actually; it uses a per-cpu one in the !wait case.
The subsequent csd_lock() ensures it will wait for any prior user to
complete, so only if you're doing multiple smp_call_function_single()
invocations back-to-back will they queue up.
> This affects the following callers:
<snip>
> kernel/stop_machine.c:stop_two_cpus()
That site should work with .wait=1 just fine, but given the above, the
.wait=0 doesn't appear problematic at all.
next prev parent reply other threads:[~2014-02-28 12:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-04 16:46 smp_call_function_single with wait=0 considered harmful Christoph Hellwig
2013-12-05 21:43 ` Bjorn Helgaas
2013-12-06 10:56 ` Christoph Hellwig
2014-02-28 12:26 ` Peter Zijlstra [this message]
2014-02-28 12:39 ` Peter Zijlstra
2014-02-28 17:06 ` Rik van Riel
2014-02-28 17:34 ` Prarit Bhargava
2014-03-11 12:36 ` [tip:sched/core] stop_machine: Fix^2 race between stop_two_cpus() and stop_cpus() tip-bot for Peter Zijlstra
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=20140228122624.GF9987@twins.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=aaro.koskinen@iki.fi \
--cc=akpm@linux-foundation.org \
--cc=bhelgaas@google.com \
--cc=david.daney@cavium.com \
--cc=hch@infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=rric@kernel.org \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.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.