On Wed, 14 Dec 2011 13:57:03 +0100, Daniel Vetter <daniel.vet...@ffwll.ch> wrote:
> The problem this patch solves is that the forcewake accounting > necessary for register reads is protected by dev->struct_mutex. But the > hangcheck and error_capture code need to access registers without > grabbing this mutex because we hold it while waiting for the gpu. > So a new lock is required. Because currently the error_state capture > is called from the error irq handler and the hangcheck code runs from > a timer, it needs to be an irqsafe spinlock (note that the registers > used by the irq handler (neglecting the error handling part) only uses > registers that don't need the forcewake dance). I think this description is wrong -- the only difference between using atomic objects and using a spinlock is that with the spinlock the call to ->force_wake_get is correctly serialized so that no register access can occur without the chip being awoken. Without a spinlock, a second thread can pass right through gen6_gt_force_wake_get and then go touch registers while the first thread is busy waking the chip up. -- keith.pack...@intel.com
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