From: "[email protected]" <[email protected]>
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/[email protected]
Cc: Mark Rutland <[email protected]>
Suggested-by: Steven Rostedt <[email protected]>
Acked-by: Paul E. McKenney <[email protected]> # from RCU CPU stall warning perspective
Signed-off-by: Guilherme G. Piccoli <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>
---
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);
--
2.35.1
On Wed, 14 Dec 2022 12:53:04 -0300
"Guilherme G. Piccoli" <[email protected]> wrote:
> On 14/12/2022 11:01, Steven Rostedt wrote:
> > From: "[email protected]" <[email protected]>
>
> Hi Steve, would be possible to use my full name here, like: Guilherme G.
> Piccoli <[email protected]> ?
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 <[email protected]> wrote:
> On Wed, 14 Dec 2022 12:53:04 -0300
> "Guilherme G. Piccoli" <[email protected]> wrote:
>
> > On 14/12/2022 11:01, Steven Rostedt wrote:
> > > From: "[email protected]" <[email protected]>
> >
> > Hi Steve, would be possible to use my full name here, like: Guilherme G.
> > Piccoli <[email protected]> ?
>
> 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" <[email protected]>
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/[email protected]
Cc: Mark Rutland <[email protected]>
Suggested-by: Steven Rostedt <[email protected]>
Acked-by: Paul E. McKenney <[email protected]> # from RCU CPU stall warning perspective
Signed-off-by: Guilherme G. Piccoli <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>
---
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);
--
2.35.1
On 14/12/2022 11:01, Steven Rostedt wrote:
> From: "[email protected]" <[email protected]>
Hi Steve, would be possible to use my full name here, like: Guilherme G.
Piccoli <[email protected]> ?
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/[email protected]
>
> Cc: Mark Rutland <[email protected]>
> Suggested-by: Steven Rostedt <[email protected]>
> Acked-by: Paul E. McKenney <[email protected]> # from RCU CPU stall warning perspective
> Signed-off-by: Guilherme G. Piccoli <[email protected]>
> Acked-by: Masami Hiramatsu (Google) <[email protected]>
> Signed-off-by: Steven Rostedt (Google) <[email protected]>
> ---
> 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" <[email protected]> wrote:
>
>> On 14/12/2022 11:01, Steven Rostedt wrote:
>>> From: "[email protected]" <[email protected]>
>>
>> Hi Steve, would be possible to use my full name here, like: Guilherme G.
>> Piccoli <[email protected]> ?
>
> 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!!