linux-kernel - Re: [PATCH 5.10] tracing: Add tracing_reset_all_online_cpus

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Date:   Mon, 19 Jun 2023 10:26:51 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Zheng Yejian <zhengyejian1@...wei.com>
Cc:     rostedt@...dmis.org, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 5.10] tracing: Add
 tracing_reset_all_online_cpus_unlocked() function

On Fri, Jun 16, 2023 at 04:49:31AM +0800, Zheng Yejian wrote:
> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> commit e18eb8783ec4949adebc7d7b0fdb65f65bfeefd9 upstream.
> 
> Currently the tracing_reset_all_online_cpus() requires the
> trace_types_lock held. But only one caller of this function actually has
> that lock held before calling it, and the other just takes the lock so
> that it can call it. More users of this function is needed where the lock
> is not held.
> 
> Add a tracing_reset_all_online_cpus_unlocked() function for the one use
> case that calls it without being held, and also add a lockdep_assert to
> make sure it is held when called.
> 
> Then have tracing_reset_all_online_cpus() take the lock internally, such
> that callers do not need to worry about taking it.
> 
> Link: https://lkml.kernel.org/r/20221123192741.658273220@goodmis.org
> 
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Zheng Yejian <zhengyejian1@...wei.com>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> [this patch is pre-depended by be111ebd8868d4b7c041cb3c6102e1ae27d6dc1d
> due to tracing_reset_all_online_cpus() should be called after taking lock]
> Fixes: be111ebd8868 ("tracing: Free buffers when a used dynamic event is removed")
> Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
> ---


What about for 5.15.y?  You can't apply a fix to just an older tree as
you will then have a regression when you update.

I'll drop this one from my queue, please resend a backport for all
relevent stable releases.

thanks,

greg k-h