On 17/04/2021 01:58, Luis Chamberlain wrote:
The VFS lacks support to do automatic freeze / thaw of filesystems
on the suspend / resume cycle. This can cause some issues, namely
stalls when we have reads/writes during the suspend / resume cycle.
Although for module loading / kexec the probability of this happening
is extremely low, maybe even impossible, its a known real issue with
the request_firmare() API which it does direct fs read. For this reason
only be chatty about the issue on the call used by the firmware API.
Lukas Middendorf has reported an easy situation to reproduce, which can
be caused by questionably buggy drivers which call the request_firmware()
API on resume.
[snip]
The VFS fs freeze work fixes this issue, however it requires a bit
more work, which may take a while to land upstream, and so for now
this provides a simple stop-gap solution.
We can remove this stop-gap solution once the kernel gets VFS
fs freeze / thaw support.
Reported-by: Lukas Middendorf <kernel@xxxxxxxxxxx>
Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Tested-by: Lukas Middendorf <kernel@xxxxxxxxxxx>
Works as advertised.
This prevents stalls on resume with buggy drivers (e.g. si2168) by
totally blocking uncached request_firmware() on resume. Uncached
request_firmware() will fail reliably (also in situations where it by
accident worked previously without stalling).
If firmware caching has been set up properly before suspend (either
through firmware_request_cache() or through request_firmware() outside
of a suspend/resume situation), the call to request_firmware() will
still work as expected on resume. This should not break properly
behaving drivers.
A failing firmware load is definitely preferable (and easier to debug
and fix in the respective drivers) compared to a stall on resume.
Lukas
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