From: Steven Rostedt <rostedt@goodmis.org>
To: Stefan Metzmacher <metze@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-trace-devel@vger.kernel.org,
io-uring <io-uring@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: sched_waking vs. set_event_pid crash (Re: Tracing busy processes/threads freezes/stalls the whole machine)
Date: Thu, 22 Jul 2021 21:41:34 -0400 [thread overview]
Message-ID: <20210722214134.11bc2a6d@rorschach.local.home> (raw)
In-Reply-To: <4ebea8f0-58c9-e571-fd30-0ce4f6f09c70@samba.org>
On Fri, 23 Jul 2021 00:43:13 +0200
Stefan Metzmacher <metze@samba.org> wrote:
> Hi Steve,
Hi Stefan,
>
> After some days of training:
> https://training.linuxfoundation.org/training/linux-kernel-debugging-and-security/
> I was able to get much closer to the problem :-)
>
> In order to reproduce it and get reliable kexec crash dumps,
> I needed to give the VM at least 3 cores.
>
> While running './io-uring_cp-forever link-cp.c file' (from:
> https://github.com/metze-samba/liburing/commits/io_uring-cp-forever )
> in one window, the following simple sequence triggered the problem in most cases:
>
> echo 1 > /sys/kernel/tracing/events/sched/sched_waking/enable
> echo 1 > /sys/kernel/tracing/set_event_pid
I was able to reproduce it with running hackbench in a while loop and
in another terminal, executing the above two lines.
I think I found the bug. Can you test this patch?
Thanks,
-- Steve
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 976bf8ce8039..fc32821f8240 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -299,8 +299,8 @@ static int tracepoint_add_func(struct tracepoint *tp,
* a pointer to it. This array is referenced by __DO_TRACE from
* include/linux/tracepoint.h using rcu_dereference_sched().
*/
- rcu_assign_pointer(tp->funcs, tp_funcs);
tracepoint_update_call(tp, tp_funcs, false);
+ rcu_assign_pointer(tp->funcs, tp_funcs);
static_key_enable(&tp->key);
release_probes(old);
next prev parent reply other threads:[~2021-07-23 1:41 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <293cfb1d-8a53-21e1-83c1-cdb6e2f32c65@samba.org>
2021-05-04 12:26 ` Tracing busy processes/threads freezes/stalls the whole machine Stefan Metzmacher
[not found] ` <20210504092404.6b12aba4@gandalf.local.home>
[not found] ` <f590b26d-c027-cc5a-bcbd-1dc734f72e7e@samba.org>
[not found] ` <20210504093550.5719d4bd@gandalf.local.home>
[not found] ` <f351bdfa-5223-e457-0396-a24ffa09d6b5@samba.org>
[not found] ` <8bb757fb-a83b-0ed5-5247-8273be3925c5@samba.org>
[not found] ` <90c806a0-8a2f-1257-7337-6761100217c9@samba.org>
2021-07-22 22:43 ` sched_waking vs. set_event_pid crash (Re: Tracing busy processes/threads freezes/stalls the whole machine) Stefan Metzmacher
2021-07-23 1:41 ` Steven Rostedt [this message]
2021-07-23 2:51 ` Steven Rostedt
2021-07-23 10:35 ` Stefan Metzmacher
2021-07-23 11:29 ` Steven Rostedt
2021-07-23 11:53 ` Stefan Metzmacher
2021-07-23 12:41 ` Steven Rostedt
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