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From:   Michael Chan <michael.chan@broadcom.com>
Date:   Wed, 14 Mar 2018 10:22:51 -0700
Message-ID: <CACKFLi=R2q71JH2Jbqbpy8HrzNpg1UmnoNWKhEs7ooWLWoQOqQ@mail.gmail.com>
Subject: Re: [PATCH net] tg3: prevent scheduling while atomic splat
To:     Jonathan Toppins <jtoppins@redhat.com>
Cc:     Netdev <netdev@vger.kernel.org>,
        Andy Gospodarek <andy@greyhouse.net>,
        Siva Reddy Kallam <siva.kallam@broadcom.com>,
        Prashant Sreedharan <prashant@broadcom.com>,
        Michael Chan <mchan@broadcom.com>,
        open list <linux-kernel@vger.kernel.org>
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On Wed, Mar 14, 2018 at 9:36 AM, Jonathan Toppins <jtoppins@redhat.com> wrote:
> The problem was introduced in commit
> 506b0a395f26 ("[netdrv] tg3: APE heartbeat changes"). The bug occurs
> because tp->lock spinlock is held which is obtained in tg3_start
> by way of tg3_full_lock(), line 11571. The documentation for usleep_range()
> specifically states it cannot be used inside a spinlock.
>
> Fixes: 506b0a395f26 ("[netdrv] tg3: APE heartbeat changes")
> Signed-off-by: Jonathan Toppins <jtoppins@redhat.com>
> ---
>
> Notes:
>     The thing I need reviewed from Broadcom is if the udelay should be 20
>     instead of 10, due to any timing changes introduced by the offending
>     patch.

Thanks.  10 us is correct.

As a future improvement, we might want to see if we can release the
spinlock and go back to usleep_range().  The wait time is potentially
up to 20 msec which is quite long.

Acked-by: Michael Chan <michael.chan@broadcom.com>