From 47e6d679cc4bab574bf32da863afafca4aad11b0 Mon Sep 17 00:00:00 2001 From: Matthew Auld Date: Thu, 1 Dec 2022 15:25:22 +0000 Subject: [PATCH 5/6] drm/i915: improve the catch-all evict to handle lock contention The catch-all evict can fail due to object lock contention, since it only goes as far as trylocking the object, due to us already holding the vm->mutex. Doing a full object lock can deadlock the system, since the vm->mutex is always our inner lock. Add another execbuf pass which drops the vm->mutex and then tries to grab the object will the full lock, before then retrying the eviction. Testcase: igt@igem_ppgtt@shrink-vs-evict-* References: https://gitlab.freedesktop.org/drm/intel/-/issues/7570 Signed-off-by: Matthew Auld Revision 4 of https://patchwork.freedesktop.org/series/111271/ --- .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 25 +++++++++++-- drivers/gpu/drm/i915/gem/i915_gem_mman.c | 2 +- drivers/gpu/drm/i915/i915_gem_evict.c | 37 ++++++++++++++----- drivers/gpu/drm/i915/i915_gem_evict.h | 4 +- drivers/gpu/drm/i915/i915_vma.c | 2 +- .../gpu/drm/i915/selftests/i915_gem_evict.c | 4 +- 6 files changed, 56 insertions(+), 18 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index cd75b0ca2555..885fe8855718 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -741,25 +741,44 @@ static int eb_reserve(struct i915_execbuffer *eb) * * Defragmenting is skipped if all objects are pinned at a fixed location. */ - for (pass = 0; pass <= 2; pass++) { + for (pass = 0; pass <= 3; pass++) { int pin_flags = PIN_USER | PIN_VALIDATE; if (pass == 0) pin_flags |= PIN_NONBLOCK; if (pass >= 1) - unpinned = eb_unbind(eb, pass == 2); + unpinned = eb_unbind(eb, pass >= 2); if (pass == 2) { err = mutex_lock_interruptible(&eb->context->vm->mutex); if (!err) { - err = i915_gem_evict_vm(eb->context->vm, &eb->ww); + err = i915_gem_evict_vm(eb->context->vm, &eb->ww, NULL); mutex_unlock(&eb->context->vm->mutex); } if (err) return err; } + if (pass == 3) { +retry: + err = mutex_lock_interruptible(&eb->context->vm->mutex); + if (!err) { + struct drm_i915_gem_object *busy_bo = NULL; + + err = i915_gem_evict_vm(eb->context->vm, &eb->ww, &busy_bo); + mutex_unlock(&eb->context->vm->mutex); + if (err && busy_bo) { + err = i915_gem_object_lock(busy_bo, &eb->ww); + i915_gem_object_put(busy_bo); + if (!err) + goto retry; + } + } + if (err) + return err; + } + list_for_each_entry(ev, &eb->unbound, bind_link) { err = eb_reserve_vma(eb, ev, pin_flags); if (err) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c index 0c5c43852e24..6f579cb8f2ff 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c @@ -369,7 +369,7 @@ static vm_fault_t vm_fault_gtt(struct vm_fault *vmf) if (vma == ERR_PTR(-ENOSPC)) { ret = mutex_lock_interruptible(&ggtt->vm.mutex); if (!ret) { - ret = i915_gem_evict_vm(&ggtt->vm, &ww); + ret = i915_gem_evict_vm(&ggtt->vm, &ww, NULL); mutex_unlock(&ggtt->vm.mutex); } if (ret) diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c index f025ee4fa526..a4b4d9b7d26c 100644 --- a/drivers/gpu/drm/i915/i915_gem_evict.c +++ b/drivers/gpu/drm/i915/i915_gem_evict.c @@ -416,6 +416,11 @@ int i915_gem_evict_for_node(struct i915_address_space *vm, * @vm: Address space to cleanse * @ww: An optional struct i915_gem_ww_ctx. If not NULL, i915_gem_evict_vm * will be able to evict vma's locked by the ww as well. + * @busy_bo: Optional pointer to struct drm_i915_gem_object. If not NULL, then + * in the event i915_gem_evict_vm() is unable to trylock an object for eviction, + * then @busy_bo will point to it. -EBUSY is also returned. The caller must drop + * the vm->mutex, before trying again to acquire the contended lock. The caller + * also owns a reference to the object. * * This function evicts all vmas from a vm. * @@ -425,7 +430,8 @@ int i915_gem_evict_for_node(struct i915_address_space *vm, * To clarify: This is for freeing up virtual address space, not for freeing * memory in e.g. the shrinker. */ -int i915_gem_evict_vm(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww) +int i915_gem_evict_vm(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww, + struct drm_i915_gem_object **busy_bo) { int ret = 0; @@ -457,15 +463,22 @@ int i915_gem_evict_vm(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww) * the resv is shared among multiple objects, we still * need the object ref. */ - if (dying_vma(vma) || + if (!i915_gem_object_get_rcu(vma->obj) || (ww && (dma_resv_locking_ctx(vma->obj->base.resv) == &ww->ctx))) { __i915_vma_pin(vma); list_add(&vma->evict_link, &locked_eviction_list); continue; } - if (!i915_gem_object_trylock(vma->obj, ww)) + if (!i915_gem_object_trylock(vma->obj, ww)) { + if (busy_bo) { + *busy_bo = vma->obj; /* holds ref */ + ret = -EBUSY; + break; + } + i915_gem_object_put(vma->obj); continue; + } __i915_vma_pin(vma); list_add(&vma->evict_link, &eviction_list); @@ -473,25 +486,29 @@ int i915_gem_evict_vm(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww) if (list_empty(&eviction_list) && list_empty(&locked_eviction_list)) break; - ret = 0; /* Unbind locked objects first, before unlocking the eviction_list */ list_for_each_entry_safe(vma, vn, &locked_eviction_list, evict_link) { __i915_vma_unpin(vma); - if (ret == 0) + if (ret == 0) { ret = __i915_vma_unbind(vma); - if (ret != -EINTR) /* "Get me out of here!" */ - ret = 0; + if (ret != -EINTR) /* "Get me out of here!" */ + ret = 0; + } + if (!dying_vma(vma)) + i915_gem_object_put(vma->obj); } list_for_each_entry_safe(vma, vn, &eviction_list, evict_link) { __i915_vma_unpin(vma); - if (ret == 0) + if (ret == 0) { ret = __i915_vma_unbind(vma); - if (ret != -EINTR) /* "Get me out of here!" */ - ret = 0; + if (ret != -EINTR) /* "Get me out of here!" */ + ret = 0; + } i915_gem_object_unlock(vma->obj); + i915_gem_object_put(vma->obj); } } while (ret == 0); diff --git a/drivers/gpu/drm/i915/i915_gem_evict.h b/drivers/gpu/drm/i915/i915_gem_evict.h index e593c530f9bd..bf0ee0e4fe60 100644 --- a/drivers/gpu/drm/i915/i915_gem_evict.h +++ b/drivers/gpu/drm/i915/i915_gem_evict.h @@ -11,6 +11,7 @@ struct drm_mm_node; struct i915_address_space; struct i915_gem_ww_ctx; +struct drm_i915_gem_object; int __must_check i915_gem_evict_something(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww, @@ -23,6 +24,7 @@ int __must_check i915_gem_evict_for_node(struct i915_address_space *vm, struct drm_mm_node *node, unsigned int flags); int i915_gem_evict_vm(struct i915_address_space *vm, - struct i915_gem_ww_ctx *ww); + struct i915_gem_ww_ctx *ww, + struct drm_i915_gem_object **busy_bo); #endif /* __I915_GEM_EVICT_H__ */ diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c index 373582cfd8f3..240b7b8ed281 100644 --- a/drivers/gpu/drm/i915/i915_vma.c +++ b/drivers/gpu/drm/i915/i915_vma.c @@ -1569,7 +1569,7 @@ static int __i915_ggtt_pin(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, * locked objects when called from execbuf when pinning * is removed. This would probably regress badly. */ - i915_gem_evict_vm(vm, NULL); + i915_gem_evict_vm(vm, NULL, NULL); mutex_unlock(&vm->mutex); } } while (1); diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c index 8c6517d29b8e..37068542aafe 100644 --- a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c +++ b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c @@ -344,7 +344,7 @@ static int igt_evict_vm(void *arg) /* Everything is pinned, nothing should happen */ mutex_lock(&ggtt->vm.mutex); - err = i915_gem_evict_vm(&ggtt->vm, NULL); + err = i915_gem_evict_vm(&ggtt->vm, NULL, NULL); mutex_unlock(&ggtt->vm.mutex); if (err) { pr_err("i915_gem_evict_vm on a full GGTT returned err=%d]\n", @@ -356,7 +356,7 @@ static int igt_evict_vm(void *arg) for_i915_gem_ww(&ww, err, false) { mutex_lock(&ggtt->vm.mutex); - err = i915_gem_evict_vm(&ggtt->vm, &ww); + err = i915_gem_evict_vm(&ggtt->vm, &ww, NULL); mutex_unlock(&ggtt->vm.mutex); } -- 2.38.1