linux-kernel - Re: [PATCH v2] tg3: driver sleeps indefinitely when EEH errors exceed eeh_max

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Message-ID: <CACKFLimJTiRx1L+FFOZfR3-yrR9u+TY_Fdy3OSgH49v9QLKGwg@mail.gmail.com>
Date:   Mon, 27 Jul 2020 00:26:22 -0700
From:   Michael Chan <michael.chan@...adcom.com>
To:     David Christensen <drc@...ux.vnet.ibm.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        Siva Reddy Kallam <siva.kallam@...adcom.com>,
        Prashant Sreedharan <prashant@...adcom.com>,
        Michael Chan <mchan@...adcom.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tg3: driver sleeps indefinitely when EEH errors exceed eeh_max_freezes

On Fri, Jul 24, 2020 at 5:19 PM David Christensen
<drc@...ux.vnet.ibm.com> wrote:

> In the working case, tg3_init_hw() returns successfully, resulting in
> every instance of napi_disable() being followed by an instance of
> napi_enable().
>
> In the failing case, tg3_hw_init() returns an error. (This is not
> surprising since the system is now preventing the adapter from accessing
> its MMIO registers.  I'm curious why it doesn't always fail.)  When
> tg3_hw_init() fails, tg3_netif_start() is not called, and we end up with
> two sequential calls to napi_disable(), resulting in multiple hung task
> messages.
>

If the driver fails to initialize the chip completely, the tg3_flags
should indicate we are in this failed state.  We already have
TG3_FLAG_INIT_COMPLETE.  Perhaps, we can expand the use of this flag
to cover the scenario that you described above.  We can clear
TG3_FLAG_INIT_COMPLETE before calling tg3_halt() and only set it back
when tg3_hw_init() completes successfully.  This is the rough idea,
but a more detailed analysis on how this flag is used needs to be done
first.

Assuming this works, the EEH handler can check TG3_FLAG_INIT_COMPLETE
to see if we should call tg3_netif_stop().

Another way to fix it is to call dev_close() if tg3_reset_task() fails
to re-initialize the device.