From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
To: linux-kernel@vger.kernel.org, rostedt@goodmis.org
Cc: rcu@vger.kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net,
"Guilherme G. Piccoli" <gpiccoli@igalia.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels
Date: Tue, 15 Nov 2022 17:48:47 -0300 [thread overview]
Message-ID: <20221115204847.593616-1-gpiccoli@igalia.com> (raw)
The function match_records() may take a while due to a large
number of string comparisons, so when in PREEMPT_VOLUNTARY
kernels we could face RCU stalls due to that.
Add a cond_resched() to prevent that.
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org> # from RCU CPU stall warning perspective
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
---
Hi Steve / Paul, thanks for the discussions on the first thread [0],
much appreciated! Here is the "official" version.
Steve: lemme know if it's good for you, and in case you prefer to
send it yourself (since you proposed it on IRC), fine by me!
Paul: kept your ACK (thanks for that BTW) even though I changed the
place of cond_resched() to align with Steve's preference. Lemme know
in case you want to drop this ACK.
Cheers,
Guilherme
[0] https://lore.kernel.org/lkml/1ef5fe19-a82f-835e-fda5-455e9c2b94b4@igalia.com/
kernel/trace/ftrace.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7dc023641bf1..80639bdb85f6 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4192,6 +4192,7 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod)
}
found = 1;
}
+ cond_resched();
} while_for_each_ftrace_rec();
out_unlock:
mutex_unlock(&ftrace_lock);
--
2.38.0
next reply other threads:[~2022-11-15 20:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-15 20:48 Guilherme G. Piccoli [this message]
2022-11-16 6:36 ` [PATCH] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels Masami Hiramatsu
2022-11-16 12:45 ` Guilherme G. Piccoli
2022-11-22 13:16 ` Guilherme G. Piccoli
2022-11-22 15:49 ` Steven Rostedt
2022-11-22 17:21 ` Guilherme G. Piccoli
2022-12-13 22:04 ` Guilherme G. Piccoli
2022-12-13 22:34 ` Steven Rostedt
2022-12-13 23:41 ` Guilherme G. Piccoli
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=20221115204847.593616-1-gpiccoli@igalia.com \
--to=gpiccoli@igalia.com \
--cc=kernel-dev@igalia.com \
--cc=kernel@gpiccoli.net \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mhiramat@kernel.org \
--cc=paulmck@kernel.org \
--cc=rcu@vger.kernel.org \
--cc=rostedt@goodmis.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).