From: Tony Lindgren <tony@atomide.com>
To: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Rajendra Nayak <rnayak@codeaurora.org>,
Paul Walmsley <paul@pwsan.com>,
linux-omap@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2] ARM: avoid Cortex-A9 livelock on tight dmb loops
Date: Fri, 25 Jan 2019 15:20:20 -0800 [thread overview]
Message-ID: <20190125232020.GX5720@atomide.com> (raw)
In-Reply-To: <E1gn8dp-0004Ai-AW@rmk-PC.armlinux.org.uk>
* Russell King <rmk+kernel@armlinux.org.uk> [190125 21:04]:
> Executing loops such as:
>
> while (1)
> cpu_relax();
>
> with interrupts disabled results in a livelock of the entire system,
> as other CPUs are prevented making progress. This is most noticable
> as a failure of crashdump kexec, which stops just after issuing:
>
> Loading crashdump kernel...
>
> to the system console. A workaround for this is to use 10 nops in
> cpu_relax().
>
> We also use wfe() in while (1) loops to avoid burning cycles in a
> tight loop, giving the CPU a hint that we're not doing anything
> useful.
>
> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
> ---
> It's been a while since this was posted, Will's suggestion was to use
> 10 nops in cpu_relax() last time around. I still prefer wfe() in
> these infinite-not-doing-anything-ever loops.
Works for me:
Tested-by: Tony Lindgren <tony@atomide.com>
_______________________________________________
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:[~2019-01-25 23:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-25 21:03 [PATCH v2] ARM: avoid Cortex-A9 livelock on tight dmb loops Russell King
2019-01-25 23:20 ` Tony Lindgren [this message]
2019-01-26 21:00 ` Paul Walmsley
2019-01-26 23:51 ` Russell King - ARM Linux admin
2019-01-27 1:15 ` Paul Walmsley
2019-01-27 15:28 ` Russell King - ARM Linux admin
2019-01-31 13:58 ` Will Deacon
2019-01-31 22:58 ` Russell King - ARM Linux admin
2019-02-01 10:19 ` Will Deacon
2019-02-01 21:20 ` Russell King - ARM Linux admin
-- strict thread matches above, loose matches on Subject: below --
2018-06-01 11:00 Russell King
2018-06-01 15:35 ` Tony Lindgren
2018-06-01 15:55 ` Russell King - ARM Linux
2018-06-01 16:12 ` Tony Lindgren
2018-06-04 9:42 ` Will Deacon
2018-06-04 18:08 ` Russell King - ARM Linux
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=20190125232020.GX5720@atomide.com \
--to=tony@atomide.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-omap@vger.kernel.org \
--cc=paul@pwsan.com \
--cc=rmk+kernel@armlinux.org.uk \
--cc=rnayak@codeaurora.org \
--cc=will.deacon@arm.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).