a687a43a48
For reasons unknown Sandybridge GT1 (at least) will eventually hang when it encounters a ring wraparound at offset 0. The test case that reproduces the bug reliably forces a large number of interrupted context switches, thereby causing very frequent ring wraparounds, but there are similar bug reports in the wild with the same symptoms, seqno writes stop just before the wrap and the ringbuffer at address 0. It is also timing crucial, but adding various delays hasn't helped pinpoint where the window lies. Whether the fault is restricted to the ringbuffer itself or the GTT addressing is unclear, but moving the ringbuffer fixes all the hangs I have been able to reproduce. References: (e.g.) https://bugs.freedesktop.org/show_bug.cgi?id=93262 Testcase: igt/gem_exec_whisper/render-contexts-interruptible #snb-gt1 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: stable@vger.kernel.org Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1460565315-7748-12-git-send-email-chris@chris-wilson.co.uk |
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