[PATCH libdrm] atomic: fix atomic_add_unless() fallback's return value

[Emil Velikov]

[+ Lionel]

On 16 March 2017 at 16:46, Eric Engestrom <eric.engestrom at imgtec.com> wrote:
> On Thursday, 2017-03-16 00:08:59 +0000, Eric Engestrom wrote:
>> According to the kernel documentation:
>>   Returns non-zero if @v was not @u, and zero otherwise.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100077
>> Fixes: 63fc571863aa64683400 ("atomic: add atomic_add_unless()")
>> Signed-off-by: David Shao <davshao at gmail.com>
>> Reviewed-by: Eric Engestrom <eric at engestrom.ch>
>> Signed-off-by: Eric Engestrom <eric at engestrom.ch>
>
> That last s-o-b was added automatically, by mistake. I'll remove it when
> pushing this.
>
> This patch seems trivial to verify, can someone confirm this is right?
>
> /me is about ~94% sure, but doesn't know much about atomic ops and their
> return value convention.
>
> I checked the kernel and it does what libdrm does after this patch, so
> either one should be fixed; I'm assuming kernel is right and libdrm
> needs fixing, hence this patch.
>
Changing the function matches the documentation, yet it doesn't [seem
to] align with how it's used.
I'm fairly sure that this will break libdrm_intel.

Lionel, can you take a look at this patch please ?
https://patchwork.freedesktop.org/patch/144252/

Emil