mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-03 17:04:50 -04:00
cbb60b4b98
When we retire the last request on the ring, before we ever access that ring again we know it will be completely idle and so we can advance the ring->head fully to the end (i.e. ring->tail) and not just to the start of the breadcrumb. This allows us to skip re-emitting the breadcrumb after resetting the GPU if the ring was entirely idle. This prevents us from overwriting a seqno wraparound by re-executing a stale breadcrumb, i.e. submit_request(1) intel_engine_init_global_seqno(0) i915_reset() would then leave 1 in the HWS, but the next request to execute would also be with seqno 1. The sanity checks upon submission detect this as a timewarp and explode. By setting the ring as empty, upon reset the HWS is left as 0, leaving it consistent with the timeline. v2: Fix check for deleting last element of list. We know that this request is always the first element of the ring, so only if next points back to the start will this be the only request in flight. v3: Remove opencoding of list_is_last() v4: Move the block to its own function for some clarity. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100144 Testcase: igt/gem_exec_whisper/hang-* Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170406170028.26871-1-chris@chris-wilson.co.uk Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.