From: Steven Rostedt <rostedt@goodmis.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Bharata B Rao <bharata@linux.vnet.ibm.com>,
Phil Auld <pauld@redhat.com>,
Daniel Thompson <daniel.thompson@linaro.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] sched/debug: Use sched_debug_lock to serialize use of cgroup_path[] only
Date: Fri, 2 Apr 2021 16:40:14 -0400 [thread overview]
Message-ID: <20210402164014.53c84f05@gandalf.local.home> (raw)
In-Reply-To: <20210401181030.7689-1-longman@redhat.com>
On Thu, 1 Apr 2021 14:10:30 -0400
Waiman Long <longman@redhat.com> wrote:
> The handling of sysrq key can be activated by echoing the key to
> /proc/sysrq-trigger or via the magic key sequence typed into a terminal
> that is connected to the system in some way (serial, USB or other mean).
> In the former case, the handling is done in a user context. In the
> latter case, it is likely to be in an interrupt context.
>
> There should be no more than one instance of sysrq key processing via
> a terminal, but multiple instances of /proc/sysrq-trigger is possible.
>
> Currently in print_cpu() of kernel/sched/debug.c, sched_debug_lock is
> taken with interrupt disabled for the whole duration of the calls to
> print_*_stats() and print_rq() which could last for the quite some time
> if the information dump happens on the serial console.
>
> If the system has many cpus and the sched_debug_lock is somehow busy
> (e.g. parallel sysrq-t), the system may hit a hard lockup panic
> depending on the actually serial console implementation of the
> system. For instance,
Wouldn't placing strategically located "touch_nmi_watchdog()"s around fix
this?
-- Steve
next prev parent reply other threads:[~2021-04-02 20:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 18:10 [PATCH v3] sched/debug: Use sched_debug_lock to serialize use of cgroup_path[] only Waiman Long
2021-04-02 20:40 ` Steven Rostedt [this message]
2021-04-03 3:09 ` Waiman Long
2021-04-04 16:02 ` Steven Rostedt
2021-04-05 1:27 ` Waiman Long
2021-04-05 1:29 ` Waiman Long
2021-04-05 15:59 ` Steven Rostedt
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=20210402164014.53c84f05@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=bharata@linux.vnet.ibm.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=daniel.thompson@linaro.org \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=longman@redhat.com \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=pauld@redhat.com \
--cc=peterz@infradead.org \
--cc=vincent.guittot@linaro.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).