From: Vasily Gorbik <gor@linux.ibm.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Heiko Carstens <hca@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
Sumanth Korikkar <sumanthk@linux.ibm.com>,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] livepatch: Fix idle cpu's tasks transition
Date: Thu, 9 Sep 2021 11:16:01 +0200 [thread overview]
Message-ID: <patch.git-a4aad6b1540d.your-ad-here.call-01631177886-ext-3083@work.hours> (raw)
On an idle system with large amount of cpus it might happen that
klp_update_patch_state() is not reached in do_idle() for a long periods
of time. With debug messages enabled log is filled with:
[ 499.442643] livepatch: klp_try_switch_task: swapper/63:0 is running
without any signs of progress. Ending up with "failed to complete
transition".
On s390 LPAR with 128 cpus not a single transition is able to complete
and livepatch kselftests fail. Tests on idling x86 kvm instance with 128
cpus demonstrate similar symptoms with and without CONFIG_NO_HZ.
To deal with that, since runqueue is already locked in
klp_try_switch_task() identify idling cpus and trigger rescheduling
potentially waking them up and making sure idle tasks break out of
do_idle() inner loop and reach klp_update_patch_state(). This helps to
speed up transition time while avoiding unnecessary extra system load.
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
Previous discussion and RFC PATCH:
lkml.kernel.org/r/patch.git-b76842ceb035.your-ad-here.call-01625661932-ext-1304@work.hours
kernel/livepatch/transition.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 3a4beb9395c4..c5832b2dd081 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -308,6 +308,8 @@ static bool klp_try_switch_task(struct task_struct *task)
rq = task_rq_lock(task, &flags);
if (task_running(rq, task) && task != current) {
+ if (is_idle_task(task))
+ resched_curr(rq);
snprintf(err_buf, STACK_ERR_BUF_SIZE,
"%s: %s:%d is running\n", __func__, task->comm,
task->pid);
--
2.25.4
next reply other threads:[~2021-09-09 9:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 9:16 Vasily Gorbik [this message]
2021-09-10 9:17 ` [PATCH] livepatch: Fix idle cpu's tasks transition Petr Mladek
2021-09-10 9:32 ` Miroslav Benes
2021-09-10 16:03 ` Josh Poimboeuf
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=patch.git-a4aad6b1540d.your-ad-here.call-01631177886-ext-3083@work.hours \
--to=gor@linux.ibm.com \
--cc=fweisbec@gmail.com \
--cc=hca@linux.ibm.com \
--cc=jikos@kernel.org \
--cc=joe.lawrence@redhat.com \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=live-patching@vger.kernel.org \
--cc=mbenes@suse.cz \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=sumanthk@linux.ibm.com \
--cc=svens@linux.ibm.com \
--cc=tglx@linutronix.de \
/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).