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Date:   Mon, 18 May 2020 16:51:54 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     jeyu@...nel.org, akpm@...ux-foundation.org, arnd@...db.de,
        rostedt@...dmis.org, mingo@...hat.com, aquini@...hat.com,
        cai@....pw, dyoung@...hat.com, bhe@...hat.com,
        peterz@...radead.org, tglx@...utronix.de, gpiccoli@...onical.com,
        pmladek@...e.com, tiwai@...e.de, schlad@...e.de,
        andriy.shevchenko@...ux.intel.com, keescook@...omium.org,
        daniel.vetter@...ll.ch, will@...nel.org,
        mchehab+samsung@...nel.org, kvalo@...eaurora.org,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        ath10k@...ts.infradead.org
Subject: Re: [PATCH v2 12/15] ath10k: use new module_firmware_crashed()

On Sat, May 16, 2020 at 03:24:01PM +0200, Johannes Berg wrote:
> On Fri, 2020-05-15 at 21:28 +0000, Luis Chamberlain wrote:> module_firmware_crashed
> 
> You didn't CC me or the wireless list on the rest of the patches, so I'm
> replying to a random one, but ...
> 
> What is the point here?
> 
> This should in no way affect the integrity of the system/kernel, for
> most devices anyway.

Keyword you used here is "most device". And in the worst case, *who*
knows what other odd things may happen afterwards.

> So what if ath10k's firmware crashes? If there's a driver bug it will
> not handle it right (and probably crash, WARN_ON, or something else),
> but if the driver is working right then that will not affect the kernel
> at all.

Sometimes the device can go into a state which requires driver removal
and addition to get things back up.

> So maybe I can understand that maybe you want an easy way to discover -
> per device - that the firmware crashed, but that still doesn't warrant a
> complete kernel taint.

That is one reason, another is that a taint helps support cases *fast*
easily detect if the issue was a firmware crash, instead of scraping
logs for driver specific ways to say the firmware has crashed.

> Instead of the kernel taint, IMHO you should provide an annotation in
> sysfs (or somewhere else) for the *struct device* that had its firmware
> crash.

It would seem the way some folks are thinking about getting more details
would be through devlink.

> Or maybe, if it's too complex to walk the entire hierarchy
> checking for that, have a uevent,  or add the ability for the kernel to
> print out elsewhere in debugfs the list of devices that crashed at some
> point... All of that is fine, but a kernel taint?

debugfs is optional, a taint is simple, and device agnostic. From a
support perspective it is very easy to see if a possible issue may
be device firmware specific.

  Luis

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