On 1/24/20 2:01 PM, Chris Wilson wrote:
Since drm_global_mutex is a true global mutex across devices, we don't
want to acquire it unless absolutely necessary. For maintaining the
device local open_count, we can use atomic operations on the counter
itself, except when making the transition to/from 0. Here, we tackle the
easy portion of delaying acquiring the drm_global_mutex for the final
release by using atomic_dec_and_mutex_lock(), leaving the global
serialisation across the device opens.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Hellström (VMware) <thomas_os@xxxxxxxxxxxx>
For the series:
Reviewed-by: Thomas Hellström <thellstrom@xxxxxxxxxx>
Now the only remaining (though pre-existing) problem I can see is that
there is no corresponding mutex lock in drm_open() so that firstopen
might race with lastclose.. Or I might be missing something..
/Thomas
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