linux-kernel - Re: [PATCH 1/2] ixgbe: release lock for the duration of ixgbe_suspend

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Message-ID: <CAGM2rea3XXJ7OqGeAdexyOUb1_7W_84t5HAb_hp7Rb=TkTM86Q@mail.gmail.com>
Date:   Thu, 03 May 2018 13:30:30 +0000
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     alexander.duyck@...il.com
Cc:     Steven Sistare <steven.sistare@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>, jeffrey.t.kirsher@...el.com,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH 1/2] ixgbe: release lock for the duration of ixgbe_suspend_close()

Hi Alex,

> I'm not a fan of dropping the mutex while we go through
> ixgbe_close_suspend. I'm concerned it will result in us having a
> number of races on shutdown.

I would agree, but ixgbe_close_suspend() is already called without this
mutex from ixgbe_close(). This path is executed also during machine
shutdown but when kexec'ed. So, it is either an existing bug or there are
no races. But, because ixgbe_close() is called from the userland, and a
little earlier than ixgbe_shutdown() I think this means there are no races.

> If anything, I think we would need to find a replacement for the mutex
> that can operate at the per-netdev level if you are wanting to
> parallelize this.

Yes, if lock is necessary, it can be replaced in this place (and added to
ixgbe_close())  with something scalable.

Thank you,
Pavel