From: Robin Murphy <robin.murphy@arm.com>
To: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Sebastian Frias <sf84@laposte.net>,
linux-pm <linux-pm@vger.kernel.org>,
Thibaud Cornic <thibaud_cornic@sigmadesigns.com>,
Mason <slash.tmp@free.fr>, arm-soc <arm@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3 1/2] ARM: tango: add HOTPLUG_CPU support
Date: Tue, 28 Jun 2016 16:16:50 +0100 [thread overview]
Message-ID: <577294E2.5030405@arm.com> (raw)
In-Reply-To: <577291F1.8060105@sigmadesigns.com>
On 28/06/16 16:04, Marc Gonzalez wrote:
> On 28/06/2016 14:30, Robin Murphy wrote:
>
>> On 28/06/16 12:59, Marc Gonzalez wrote:
>>
>>> +#ifdef CONFIG_HOTPLUG_CPU
>>> +/*
>>> + * cpu_kill() and cpu_die() run concurrently on different cores.
>>> + * Firmware will only "kill" a core once it has properly "died".
>>> + * Keep trying to kill a core until the operation succeeds, but
>>> + * sleep between tries to give the core time to die.
>>> + */
>>> +static int tango_cpu_kill(unsigned int cpu)
>>> +{
>>> + do {
>>> + msleep(10);
>>> + } while (tango_aux_core_kill(cpu) != 0);
>>
>> Does the firmware guarantee that this will succeed (or at least report
>> success) in finite time, regardless of how messed up the system might
>> be? I'd imagine this should probably have either a timeout or a comment
>> clarifying why it doesn't need a timeout.
>
> Good point.
>
> The FW allows only one thread at a time. If a thread is wedged inside
> the FW, no other thread can use the FW. In that situation, cpu0 would
> remain stuck inside tango_cpu_kill().
>
> Note, that if tango_cpu_kill() starts failing, then secondary cores
> will remain "zombies". So the system is mostly hosed anyway...
> Only cpu0 will be available.
Indeed; my thought was that if CPU1 somehow ends up wedged such that
tango_aux_core_die() never completes, then CPU0 eventually timing out
and being able to limp through a clean(ish) reboot is probably
preferable to spinning in cpu_kill() forever.
Robin.
>
> Regards.
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
next prev parent reply other threads:[~2016-06-28 15:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <57726597.8030501@sigmadesigns.com>
2016-06-28 11:59 ` [PATCH v3 1/2] ARM: tango: add HOTPLUG_CPU support Marc Gonzalez
2016-06-28 12:30 ` Robin Murphy
2016-06-28 15:04 ` Marc Gonzalez
2016-06-28 15:16 ` Robin Murphy [this message]
2016-06-29 12:28 ` Marc Gonzalez
2016-06-29 12:21 ` [PATCH v4 " Marc Gonzalez
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=577294E2.5030405@arm.com \
--to=robin.murphy@arm.com \
--cc=arm@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-pm@vger.kernel.org \
--cc=marc_gonzalez@sigmadesigns.com \
--cc=mark.rutland@arm.com \
--cc=sf84@laposte.net \
--cc=slash.tmp@free.fr \
--cc=thibaud_cornic@sigmadesigns.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