Re: [PATCH v3 12/28] drm/i915: Convert mmio_flip::seqno to struct request

Daniel Vetter
2014-11-26T12:49:54Z

On Wed, Nov 26, 2014 at 1:12 PM, John Harrison
<John.C.Harrison@intel.com> wrote:
> The unref_irq is needed for the flip_queued_req as that is still
> dereferenced from interrupt time. Possibly this one could now be downgraded
> to a mutex lock but before the recent rebase, the mmio_flip request was also
> being dereferenced at interrupt time so definitely needed the irq friendly
> version. Is there a worry that waiting for the mutex lock could stall the
> flip handler so long that it misses the next flip?

Yup this is only possible very recently. I've simply dropped the _irq
and wrapped with struct_mutex locking, but a lockless unref (which
only grabs the lock on the final kput in the free function) like Chris
suggested would indeed be tidier.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch