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From:   John Ogness <john.ogness@linutronix.de>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Jan Luebbe <jlu@pengutronix.de>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andy Lutomirski <luto@kernel.org>, kernel@pengutronix.de,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] proc: report eip and esp for all threads when coredumping
References: <20190522161614.628-1-jlu@pengutronix.de>
        <875zpzif8v.fsf@linutronix.de>
        <20190525143220.e771b7915d17f22dad1438fa@linux-foundation.org>
Date:   Sun, 26 May 2019 21:41:28 +0200
In-Reply-To: <20190525143220.e771b7915d17f22dad1438fa@linux-foundation.org>
        (Andrew Morton's message of "Sat, 25 May 2019 14:32:20 -0700")
Message-ID: <87d0k5f1g7.fsf@linutronix.de>
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Hi Andrew,

On 2019-05-25, Andrew Morton <akpm@linux-foundation.org> wrote:
> Please send along a signed-off-by: for this?

From my response:

On 2019-05-25, John Ogness <john.ogness@linutronix.de> wrote:
> AFAICT core_state does not need to be set before the other lines. But
> there may be some side effects that I overlooked!

The changes I showed were more of a suggestion for Jan than an actual
patch. For a signed-off-by I'll need to do some deeper looking to make
sure what I suggested was safe. Also, we probably need a barrier to make
sure the task flag is cleared before setting core_state. Or instead, we
probably should set core_state after releasing the siglock, setting it
where the PF_DUMPCORE flag is set.

It seems to me that checking for a non-NULL core_state and checking for
the PF_DUMPCORE flag are both used throughout the kernel to identify
core dumps in action. So I think it makes sense to set them "at the same
time". (Or perhaps eliminate PF_DUMPCORE altogether and just use a
non-NULL core_state to identify core dumping.)

I will take a closer look at this.

John Ogness