linux-kernel - Re: [PATCH v4] binder: tell userspace to dump current backtrace when detected oneway spamming

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Message-ID: <YG/veiWKkaJtEZkq@kroah.com>
Date:   Fri, 9 Apr 2021 08:08:58 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Hang Lu <hangl@...eaurora.org>
Cc:     tkjos@...gle.com, tkjos@...roid.com, maco@...roid.com,
        arve@...roid.com, joel@...lfernandes.org, christian@...uner.io,
        hridya@...gle.com, surenb@...gle.com, rdunlap@...radead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] binder: tell userspace to dump current backtrace when
 detected oneway spamming

On Fri, Apr 09, 2021 at 11:40:57AM +0800, Hang Lu wrote:
> When async binder buffer got exhausted, some normal oneway transactions
> will also be discarded and may cause system or application failures. By
> that time, the binder debug information we dump may not be relevant to
> the root cause. And this issue is difficult to debug if without the
> backtrace of the thread sending spam.
> 
> This change will send BR_ONEWAY_SPAM_SUSPECT to userspace when oneway
> spamming is detected, request to dump current backtrace. Oneway spamming
> will be reported only once when exceeding the threshold (target process
> dips below 80% of its oneway space, and current process is responsible for
> either more than 50 transactions, or more than 50% of the oneway space).
> And the detection will restart when the async buffer has returned to a
> healthy state.
> 
> Signed-off-by: Hang Lu <hangl@...eaurora.org>
> ---
> v4: add missing BR_FROZEN_REPLY in binder_return_strings and change the size of binder_stats.br array

Should the BR_FROZEN_REPLY string be a separate patch as it's a fix for
the "binder frozen feature", not this new feature, right?  Or does this
patch require that change and the frozen patch did not?

thanks,

greg k-h