From: Beau Belgrave <beaub@linux.microsoft.com>
To: sunliming <sunliming@kylinos.cn>
Cc: mhiramat@kernel.org, rostedt@goodmis.org, shuah@kernel.org,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, kelulanainsley@gmail.com
Subject: Re: [PATCH 1/3] tracing/user_events: Fix incorrect return value for writing operation when events are disabled
Date: Thu, 8 Jun 2023 10:19:21 -0700 [thread overview]
Message-ID: <20230608171921.GA74@W11-BEAU-MD.localdomain> (raw)
In-Reply-To: <20230608011554.1181097-2-sunliming@kylinos.cn>
On Thu, Jun 08, 2023 at 09:15:52AM +0800, sunliming wrote:
> The writing operation return the count of writes whether events are
> enabled or disabled. This is incorrect when events are disabled. Fix
> this by just return -EFAULT when events are disabled.
>
> Signed-off-by: sunliming <sunliming@kylinos.cn>
> ---
> kernel/trace/trace_events_user.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 1ac5ba5685ed..970bac0503fd 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -1957,7 +1957,8 @@ static ssize_t user_events_write_core(struct file *file, struct iov_iter *i)
>
> if (unlikely(faulted))
> return -EFAULT;
> - }
> + } else
> + return -EFAULT;
>
I'm not sure this is a good idea. Imagine this scenario:
A user process writes out a user_event and it hits a fault that gets
returned as errno (EFAULT).
The user process is likely to either forget it and say, not worth
retrying, or it will retry (potentially in a loop).
If the process does retry and it's now disabled, it might try many
times.
I think that -ENOENT is a better error to use here. That way a user
process will know it got disabled mid-write vs a fault that might want
to be re-attempted.
Thanks,
-Beau
> return ret;
> }
> --
> 2.25.1
next prev parent reply other threads:[~2023-06-08 17:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-08 1:15 [PATCH 0/3] tracing/user_events: Fix incorrect return value for sunliming
2023-06-08 1:15 ` [PATCH 1/3] tracing/user_events: Fix incorrect return value for writing operation when events are disabled sunliming
2023-06-08 17:19 ` Beau Belgrave [this message]
2023-06-13 5:52 ` sunliming
2023-06-08 1:15 ` [PATCH 2/3] selftests/user_events: Enable the event before write_fault test in ftrace self-test sunliming
2023-06-08 1:15 ` [PATCH 3/3] selftests/user_events: Add test cases when event is disabled sunliming
2023-06-08 17:21 ` Beau Belgrave
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