[PATCH] Revert "drm/radeon: Try evicting from CPU accessible to inaccessible VRAM first"

[Julien Isorce]

On 28 March 2017 at 10:36, Michel Dänzer <michel at daenzer.net> wrote:

> On 28/03/17 05:24 PM, Julien Isorce wrote:
> > Hi Michel,
> >
> > About the hard lockup, I noticed that I cannot have it with the
> > following conditions:
> >
> > 1. soft lockup fix (the 0->i change which avoids infinite loop)
> > 2. Your suggestion: (!(rbo->flags & RADEON_GEM_CPU_ACCESS)
> > 3. radeon.gartsize=512 radeon.vramlimit=1024 (any other values above do
> > not help, for example (1024, 1024) or (1024, 2048))
> >
> > Without 1 and 2, but with 3, our test reproduces the soft lockup (just
> > discovered few days ago).
> > Without 3 (and with or without 1., 2.), our test reproduces the hard
> > lockup which one does not give any info in kern.log (sometimes some NUL
> > ^@ characters but not always).
>
> What exactly does "hard lockup" mean? What are the symptoms?
>
>
Screens are frozen, cannot ssh, no mouse/keyboard, no kernel panic.
Requires hard reboot.
After reboot, nothing in /var/crash, nothing in /sys/fs/pstore, nothing in
kern.log except sometimes some nul characters ^@.
Adding traces it looks like the test app was still in a ioctl(RADEON_CS)
but it is difficult to rely on that since this is called a lot.
Using a serial console did not show additional debug messages. kgdb was not
useful but probably worth another attempt.
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