[Mesa-dev] [PATCH] glsl: fix disk cache eviction issue

[Emil Velikov]

On 9 January 2017 at 15:36, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> On 9 December 2016 at 05:58, Tapani Pälli <tapani.palli at intel.com> wrote:
>> When 'evict_random_item' attempts to remove cache content to make more
>> space, it may try to remove from new cache directory it just created
>> which only has '.tmp' content at this phase and not proper cache files,
>> this will cause eviction to fail and 'test_put_and_get' subtest
>> assumptions about cache size and item count won't hold.
>>
>> Patch fixes this issue by adding 'exception' argument for random file
>> matching so that algorithm won't pick the new directory.
>>
> Hi Tapani,
>
> I've mentioned this over at #android-ia, but adding it here for posterity.
>
>
> The issue itself is actually quite different - in my experiments with
> importing SHA1 implementation to mesa, I've noticed that there bug
> lies with a buggy (and/or undefined behaviour) SHA1 implementation
> given the input data.
>
> Namely:
> As one observes the output of _mesa_sha1_compute they will notice that
> it differs across implementations. This in itself combined with the
> (afaict) correct assumption in test_put_and_get() that the beginning
> for the SHA1blob_key_byte_zero
>
[Pressed enter to quickly]

...the SHA1 matches blob_key_byte_zero (as mentioned in the comment of
said function) makes things work ... sometimes.

So in a Tl;Dr; we want to drop the ~5 different codepaths, in favour
of a single one, used by everyone - devs, testers, and users.

-Emil