From: tglx@linutronix.de (Thomas Gleixner)
To: linux-arm-kernel@lists.infradead.org
Subject: [patch] ARM: smpboot: Enable interrupts after marking CPU online/active
Date: Tue, 15 Nov 2011 23:00:59 +0100 (CET) [thread overview]
Message-ID: <alpine.LFD.2.02.1111152259430.4902@ionos> (raw)
In-Reply-To: <4EC2DF93.2050904@codeaurora.org>
On Tue, 15 Nov 2011, Stepan Moskovchenko wrote:
> I am seeing a deadlock when executing hotplug operations with this patch
> applied. When the secondary CPU gets brought up in _cpu_up, the cpu is turned
> on
> and then the online notifier gets called, which is what marks the secondary
> CPU
> as active. If _cpu_up on the primary CPU is preempted before the secondary CPU
> is marked active, it is possible that the primary CPU will want to call
> smp_call_function (or send an IPI) to the secondary CPU because it is marked
> online. However, with this patch, the secondary CPU is still spinning on
> !cpu_active(cpu)
> with interrupts disabled. So, the primary CPU is now stuck in csd_lock_wait(),
> waiting for the secondary CPU to respond, while the secondary CPU spins with
> interrupts disabled, waiting for the primary CPU to mark it as active. So,
> while
> your approach to not call smp_function_single may work for you in your
> specific
> case, I believe there is still a problem in the general case.
>
> One suggestion for resolving this might be making smp_call_function look at
> the
> active CPUs rather than online CPUs, or to just let the secondary CPU mark
> itself as active rather than having the primary CPU do this, though this might
> defeat the original intended purpose of the active mask.
What a mess. I'll have a look tomorrow.
next prev parent reply other threads:[~2011-11-15 22:00 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-08 21:57 [patch] ARM: smpboot: Enable interrupts after marking CPU online/active Thomas Gleixner
2011-09-09 4:17 ` Santosh
2011-09-13 13:30 ` amit kachhap
2011-09-13 13:32 ` Russell King - ARM Linux
2011-09-13 17:22 ` Vincent Guittot
2011-09-13 17:53 ` Russell King - ARM Linux
2011-09-13 20:48 ` Thomas Gleixner
2011-09-13 22:37 ` Russell King - ARM Linux
2011-09-14 1:10 ` Frank Rowand
2011-09-14 6:55 ` Vincent Guittot
2011-09-23 8:40 ` Russell King - ARM Linux
2011-09-26 7:26 ` Amit Kachhap
2011-09-29 7:40 ` Kukjin Kim
2011-09-29 20:12 ` Thomas Gleixner
2011-09-30 6:42 ` Kukjin Kim
2011-10-07 9:49 ` Kukjin Kim
2011-10-07 12:17 ` Thomas Gleixner
2011-10-07 14:09 ` Amit Kachhap
2011-10-10 4:28 ` Kukjin Kim
2011-10-19 21:16 ` Dima Zavin
2011-10-20 0:32 ` Dima Zavin
2011-11-15 21:54 ` Stepan Moskovchenko
2011-11-15 22:00 ` Thomas Gleixner [this message]
2011-12-14 0:13 ` Dima Zavin
2011-12-14 0:26 ` Thomas Gleixner
2011-12-15 16:09 ` Peter Zijlstra
2011-11-15 23:27 ` Dima Zavin
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.2.02.1111152259430.4902@ionos \
--to=tglx@linutronix.de \
--cc=linux-arm-kernel@lists.infradead.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 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).