netdev - Re: [PATCH V3 08/11] EDAC/altera: Skip the panic notifier if kdump is loaded

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Message-ID: <Y3zlghMzlc1kzVJx@zn.tnic>
Date:   Tue, 22 Nov 2022 16:06:42 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Tony Luck <tony.luck@...el.com>,
        Rabara Niravkumar L <niravkumar.l.rabara@...el.com>
Cc:     Dinh Nguyen <dinguyen@...nel.org>, linux-edac@...r.kernel.org,
        kexec@...ts.infradead.org, pmladek@...e.com,
        linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org, x86@...nel.org, kernel-dev@...lia.com,
        kernel@...ccoli.net
Subject: Re: [PATCH V3 08/11] EDAC/altera: Skip the panic notifier if kdump
 is loaded

On Tue, Nov 22, 2022 at 10:33:12AM -0300, Guilherme G. Piccoli wrote:

Leaving in the whole thing for newly added people.

> On 18/09/2022 11:10, Guilherme G. Piccoli wrote:
> > On 19/08/2022 19:17, Guilherme G. Piccoli wrote:
> >> The altera_edac panic notifier performs some data collection with
> >> regards errors detected; such code relies in the regmap layer to
> >> perform reads/writes, so the code is abstracted and there is some
> >> risk level to execute that, since the panic path runs in atomic
> >> context, with interrupts/preemption and secondary CPUs disabled.
> >>
> >> Users want the information collected in this panic notifier though,
> >> so in order to balance the risk/benefit, let's skip the altera panic
> >> notifier if kdump is loaded. While at it, remove a useless header
> >> and encompass a macro inside the sole ifdef block it is used.
> >>
> >> Cc: Borislav Petkov <bp@...en8.de>
> >> Cc: Petr Mladek <pmladek@...e.com>
> >> Cc: Tony Luck <tony.luck@...el.com>
> >> Acked-by: Dinh Nguyen <dinguyen@...nel.org>
> >> Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com>
> >>
> >> ---
> >>
> >> V3:
> >> - added the ack tag from Dinh - thanks!
> >> - had a good discussion with Boris about that in V2 [0],
> >> hopefully we can continue and reach a consensus in this V3.
> >> [0] https://lore.kernel.org/lkml/46137c67-25b4-6657-33b7-cffdc7afc0d7@igalia.com/
> >>
> >> V2:
> >> - new patch, based on the discussion in [1].
> >> [1] https://lore.kernel.org/lkml/62a63fc2-346f-f375-043a-fa21385279df@igalia.com/
> >>
> >> [...]
> > 
> > Hi Dinh, Tony, Boris - sorry for the ping.
> > 
> > Appreciate reviews on this one - Dinh already ACKed the patch but Boris
> > raised some points in the past version [0], so any opinions or
> > discussions are welcome!
> 
> 
> Hi folks, monthly ping heheh
> Apologies for the re-pings, please let me know if there is anything
> required to move on this patch.

Looking at this again, I really don't like the sprinkling of

	if (kexec_crash_loaded())

in unrelated code. And I still think that the real fix here is to kill
this

	edac->panic_notifier

thing. And replace it with simply logging the error from the double bit
error interrupt handle. That DBERR IRQ thing altr_edac_a10_irq_handler().
Because this is what this panic notifier does - dump double-bit errors.

Now, if Dinh doesn't move, I guess we can ask Tony and/or Rabara (he has
sent a patch for this driver recently and Altera belongs to Intel now)
to find someone who can test such a change and we (you could give it a
try first :)) can do that change.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette