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Date:   Mon, 18 May 2020 16:51:54 +0000
From:   Luis Chamberlain <mcgrof@kernel.org>
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     jeyu@kernel.org, akpm@linux-foundation.org, arnd@arndb.de,
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        linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
        ath10k@lists.infradead.org
Subject: Re: [PATCH v2 12/15] ath10k: use new module_firmware_crashed()
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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