linux-kernel - Re: [PATCH] ftrace: Properly unset FTRACE_HASH_FL

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Date:   Mon, 26 Sep 2022 10:32:42 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Zheng Yejian <zhengyejian1@...wei.com>
Cc:     <mingo@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace: Properly unset FTRACE_HASH_FL_MOD

On Mon, 26 Sep 2022 15:20:08 +0000
Zheng Yejian <zhengyejian1@...wei.com> wrote:

> When executing following commands like what document said, but the log
> "#### all functions enabled ####" was not shown as expect:
>   1. Set a 'mod' filter:
>     $ echo 'write*:mod:ext3' > /sys/kernel/tracing/set_ftrace_filter
>   2. Invert above filter:
>     $ echo '!write*:mod:ext3' >> /sys/kernel/tracing/set_ftrace_filter
>   3. Read the file:
>     $ cat /sys/kernel/tracing/set_ftrace_filter
> 
> By some debugging, I found that flag FTRACE_HASH_FL_MOD was not unset
> after inversion like above step 2 and then result of ftrace_hash_empty()
> is incorrect.
> 
> Cc: stable@...r.kernel.org
> Fixes: 8c08f0d5c6fb ("ftrace: Have cached module filters be an active filter")
> Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>

Thanks, this definitely looks like a bug.

I'll be reviewing these patches later this week.

-- Steve