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>,
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: [RFC PATCH] livepatch: Kick idle cpu's tasks to perform transition
Date: Wed, 7 Jul 2021 14:49:38 +0200 [thread overview]
Message-ID: <patch.git-b76842ceb035.your-ad-here.call-01625661932-ext-1304@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.
To deal with that, make sure we break out of do_idle() inner loop to
reach klp_update_patch_state() by marking idle tasks as NEED_RESCHED
as well as kick cpus out of idle state.
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
kernel/livepatch/transition.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 3a4beb9395c4..793eba46e970 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -415,8 +415,11 @@ void klp_try_complete_transition(void)
for_each_possible_cpu(cpu) {
task = idle_task(cpu);
if (cpu_online(cpu)) {
- if (!klp_try_switch_task(task))
+ if (!klp_try_switch_task(task)) {
complete = false;
+ set_tsk_need_resched(task);
+ kick_process(task);
+ }
} else if (task->patch_state != klp_target_state) {
/* offline idle tasks can be switched immediately */
clear_tsk_thread_flag(task, TIF_PATCH_PENDING);
--
2.25.4
next reply other threads:[~2021-07-07 12:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 12:49 Vasily Gorbik [this message]
2021-07-08 10:12 ` [RFC PATCH] livepatch: Kick idle cpu's tasks to perform transition Petr Mladek
2021-08-06 23:59 ` Suraj Jitindar Singh
2021-08-27 12:54 ` Petr Mladek
2021-09-09 8:54 ` Vasily Gorbik
2021-09-10 8:08 ` Petr Mladek
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