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https://gitee.com/bianbu-linux/linux-6.6
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d19d71fc2b
The request->timeline is only valid until the request is retired (i.e. before it is completed). Upon retiring the request, the context may be unpinned and freed, and along with it the timeline may be freed. We therefore need to be very careful when chasing rq->timeline that the pointer does not disappear beneath us. The vast majority of users are in a protected context, either during request construction or retirement, where the timeline->mutex is held and the timeline cannot disappear. It is those few off the beaten path (where we access a second timeline) that need extra scrutiny -- to be added in the next patch after first adding the warnings about dangerous access. One complication, where we cannot use the timeline->mutex itself, is during request submission onto hardware (under spinlocks). Here, we want to check on the timeline to finalize the breadcrumb, and so we need to impose a second rule to ensure that the request->timeline is indeed valid. As we are submitting the request, it's context and timeline must be pinned, as it will be used by the hardware. Since it is pinned, we know the request->timeline must still be valid, and we cannot submit the idle barrier until after we release the engine->active.lock, ergo while submitting and holding that spinlock, a second thread cannot release the timeline. v2: Don't be lazy inside selftests; hold the timeline->mutex for as long as we need it, and tidy up acquiring the timeline with a bit of refactoring (i915_active_add_request) Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190919111912.21631-1-chris@chris-wilson.co.uk |
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| .. | ||
| selftests | ||
| i915_gem_busy.c | ||
| i915_gem_clflush.c | ||
| i915_gem_clflush.h | ||
| i915_gem_client_blt.c | ||
| i915_gem_client_blt.h | ||
| i915_gem_context.c | ||
| i915_gem_context.h | ||
| i915_gem_context_types.h | ||
| i915_gem_dmabuf.c | ||
| i915_gem_domain.c | ||
| i915_gem_execbuffer.c | ||
| i915_gem_fence.c | ||
| i915_gem_internal.c | ||
| i915_gem_ioctls.h | ||
| i915_gem_mman.c | ||
| i915_gem_object.c | ||
| i915_gem_object.h | ||
| i915_gem_object_blt.c | ||
| i915_gem_object_blt.h | ||
| i915_gem_object_types.h | ||
| i915_gem_pages.c | ||
| i915_gem_phys.c | ||
| i915_gem_pm.c | ||
| i915_gem_pm.h | ||
| i915_gem_shmem.c | ||
| i915_gem_shrinker.c | ||
| i915_gem_shrinker.h | ||
| i915_gem_stolen.c | ||
| i915_gem_stolen.h | ||
| i915_gem_throttle.c | ||
| i915_gem_tiling.c | ||
| i915_gem_userptr.c | ||
| i915_gem_wait.c | ||
| i915_gemfs.c | ||
| i915_gemfs.h | ||
| Makefile | ||