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Message-ID: <20221214140209.346584113@goodmis.org>
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Date: Wed, 14 Dec 2022 09:01:39 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mark Rutland <mark.rutland@arm.com>,
"Guilherme G. Piccoli" <gpiccoli@igalia.com>
Subject: [for-next][PATCH 6/8] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY
kernels
References: <20221214140133.608431204@goodmis.org>
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| Series |
tracing: Last minute fixes for 6.2
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Commit Message
Steven Rostedt
Dec. 14, 2022, 2:01 p.m. UTC
From: "gpiccoli@igalia.com" <gpiccoli@igalia.com> 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. Link: https://lkml.kernel.org/r/20221115204847.593616-1-gpiccoli@igalia.com Cc: Mark Rutland <mark.rutland@arm.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Paul E. McKenney <paulmck@kernel.org> # from RCU CPU stall warning perspective Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- kernel/trace/ftrace.c | 1 + 1 file changed, 1 insertion(+)
Comments
On 14/12/2022 11:01, Steven Rostedt wrote: > From: "gpiccoli@igalia.com" <gpiccoli@igalia.com> Hi Steve, would be possible to use my full name here, like: Guilherme G. Piccoli <gpiccoli@igalia.com> ? Thanks, Guilherme > > 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. > > Link: https://lkml.kernel.org/r/20221115204847.593616-1-gpiccoli@igalia.com > > Cc: Mark Rutland <mark.rutland@arm.com> > Suggested-by: Steven Rostedt <rostedt@goodmis.org> > Acked-by: Paul E. McKenney <paulmck@kernel.org> # from RCU CPU stall warning perspective > Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > kernel/trace/ftrace.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index d04552c0c275..b8e374a372e5 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -4204,6 +4204,7 @@ 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);
On Wed, 14 Dec 2022 12:53:04 -0300 "Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote: > On 14/12/2022 11:01, Steven Rostedt wrote: > > From: "gpiccoli@igalia.com" <gpiccoli@igalia.com> > > Hi Steve, would be possible to use my full name here, like: Guilherme G. > Piccoli <gpiccoli@igalia.com> ? Sure, I haven't pushed to the next repo yet. I found the reason it didn't go into my patchwork, and did a resend via a "redirect", and that must have changed the from address :-/ -- Steve
On Wed, 14 Dec 2022 11:15:44 -0500 Steven Rostedt <rostedt@goodmis.org> wrote: > On Wed, 14 Dec 2022 12:53:04 -0300 > "Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote: > > > On 14/12/2022 11:01, Steven Rostedt wrote: > > > From: "gpiccoli@igalia.com" <gpiccoli@igalia.com> > > > > Hi Steve, would be possible to use my full name here, like: Guilherme G. > > Piccoli <gpiccoli@igalia.com> ? > > Sure, I haven't pushed to the next repo yet. > > I found the reason it didn't go into my patchwork, and did a resend via a > "redirect", and that must have changed the from address :-/ > Here's the new update: -- Steve From d0b24b4e91fcb8408c4979888547f86be514e337 Mon Sep 17 00:00:00 2001 From: "Guilherme G. Piccoli" <gpiccoli@igalia.com> Date: Tue, 15 Nov 2022 17:48:47 -0300 Subject: [PATCH] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels 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. Link: https://lkml.kernel.org/r/20221115204847.593616-1-gpiccoli@igalia.com Cc: Mark Rutland <mark.rutland@arm.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Paul E. McKenney <paulmck@kernel.org> # from RCU CPU stall warning perspective Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- kernel/trace/ftrace.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index d04552c0c275..b8e374a372e5 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4204,6 +4204,7 @@ 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);
On 14/12/2022 13:15, Steven Rostedt wrote: > On Wed, 14 Dec 2022 12:53:04 -0300 > "Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote: > >> On 14/12/2022 11:01, Steven Rostedt wrote: >>> From: "gpiccoli@igalia.com" <gpiccoli@igalia.com> >> >> Hi Steve, would be possible to use my full name here, like: Guilherme G. >> Piccoli <gpiccoli@igalia.com> ? > > Sure, I haven't pushed to the next repo yet. > > I found the reason it didn't go into my patchwork, and did a resend via a > "redirect", and that must have changed the from address :-/ > > -- Steve Perfect, thanks a lot for your prompt response!!
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index d04552c0c275..b8e374a372e5 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4204,6 +4204,7 @@ 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);