// SPDX-License-Identifier: MIT /* * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst) * * Based on bo.c which bears the following copyright notice, * but is dual licensed: * * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA * All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the * "Software"), to deal in the Software without restriction, including * without limitation the rights to use, copy, modify, merge, publish, * distribute, sub license, and/or sell copies of the Software, and to * permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice (including the * next paragraph) shall be included in all copies or substantial portions * of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE * USE OR OTHER DEALINGS IN THE SOFTWARE. * **************************************************************************/ /* * Authors: Thomas Hellstrom */ #include #include #include #include #include #include /** * DOC: Reservation Object Overview * * The reservation object provides a mechanism to manage shared and * exclusive fences associated with a buffer. A reservation object * can have attached one exclusive fence (normally associated with * write operations) or N shared fences (read operations). The RCU * mechanism is used to protect read access to fences from locked * write-side updates. * * See struct dma_resv for more details. */ DEFINE_WD_CLASS(reservation_ww_class); EXPORT_SYMBOL(reservation_ww_class); /** * dma_resv_list_alloc - allocate fence list * @shared_max: number of fences we need space for * * Allocate a new dma_resv_list and make sure to correctly initialize * shared_max. */ static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max) { struct dma_resv_list *list; list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL); if (!list) return NULL; list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) / sizeof(*list->shared); return list; } /** * dma_resv_list_free - free fence list * @list: list to free * * Free a dma_resv_list and make sure to drop all references. */ static void dma_resv_list_free(struct dma_resv_list *list) { unsigned int i; if (!list) return; for (i = 0; i < list->shared_count; ++i) dma_fence_put(rcu_dereference_protected(list->shared[i], true)); kfree_rcu(list, rcu); } /** * dma_resv_init - initialize a reservation object * @obj: the reservation object */ void dma_resv_init(struct dma_resv *obj) { ww_mutex_init(&obj->lock, &reservation_ww_class); seqcount_ww_mutex_init(&obj->seq, &obj->lock); RCU_INIT_POINTER(obj->fence, NULL); RCU_INIT_POINTER(obj->fence_excl, NULL); } EXPORT_SYMBOL(dma_resv_init); /** * dma_resv_fini - destroys a reservation object * @obj: the reservation object */ void dma_resv_fini(struct dma_resv *obj) { struct dma_resv_list *fobj; struct dma_fence *excl; /* * This object should be dead and all references must have * been released to it, so no need to be protected with rcu. */ excl = rcu_dereference_protected(obj->fence_excl, 1); if (excl) dma_fence_put(excl); fobj = rcu_dereference_protected(obj->fence, 1); dma_resv_list_free(fobj); ww_mutex_destroy(&obj->lock); } EXPORT_SYMBOL(dma_resv_fini); /** * dma_resv_reserve_shared - Reserve space to add shared fences to * a dma_resv. * @obj: reservation object * @num_fences: number of fences we want to add * * Should be called before dma_resv_add_shared_fence(). Must * be called with @obj locked through dma_resv_lock(). * * Note that the preallocated slots need to be re-reserved if @obj is unlocked * at any time before calling dma_resv_add_shared_fence(). This is validated * when CONFIG_DEBUG_MUTEXES is enabled. * * RETURNS * Zero for success, or -errno */ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences) { struct dma_resv_list *old, *new; unsigned int i, j, k, max; dma_resv_assert_held(obj); old = dma_resv_shared_list(obj); if (old && old->shared_max) { if ((old->shared_count + num_fences) <= old->shared_max) return 0; max = max(old->shared_count + num_fences, old->shared_max * 2); } else { max = max(4ul, roundup_pow_of_two(num_fences)); } new = dma_resv_list_alloc(max); if (!new) return -ENOMEM; /* * no need to bump fence refcounts, rcu_read access * requires the use of kref_get_unless_zero, and the * references from the old struct are carried over to * the new. */ for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) { struct dma_fence *fence; fence = rcu_dereference_protected(old->shared[i], dma_resv_held(obj)); if (dma_fence_is_signaled(fence)) RCU_INIT_POINTER(new->shared[--k], fence); else RCU_INIT_POINTER(new->shared[j++], fence); } new->shared_count = j; /* * We are not changing the effective set of fences here so can * merely update the pointer to the new array; both existing * readers and new readers will see exactly the same set of * active (unsignaled) shared fences. Individual fences and the * old array are protected by RCU and so will not vanish under * the gaze of the rcu_read_lock() readers. */ rcu_assign_pointer(obj->fence, new); if (!old) return 0; /* Drop the references to the signaled fences */ for (i = k; i < max; ++i) { struct dma_fence *fence; fence = rcu_dereference_protected(new->shared[i], dma_resv_held(obj)); dma_fence_put(fence); } kfree_rcu(old, rcu); return 0; } EXPORT_SYMBOL(dma_resv_reserve_shared); #ifdef CONFIG_DEBUG_MUTEXES /** * dma_resv_reset_shared_max - reset shared fences for debugging * @obj: the dma_resv object to reset * * Reset the number of pre-reserved shared slots to test that drivers do * correct slot allocation using dma_resv_reserve_shared(). See also * &dma_resv_list.shared_max. */ void dma_resv_reset_shared_max(struct dma_resv *obj) { struct dma_resv_list *fences = dma_resv_shared_list(obj); dma_resv_assert_held(obj); /* Test shared fence slot reservation */ if (fences) fences->shared_max = fences->shared_count; } EXPORT_SYMBOL(dma_resv_reset_shared_max); #endif /** * dma_resv_add_shared_fence - Add a fence to a shared slot * @obj: the reservation object * @fence: the shared fence to add * * Add a fence to a shared slot, @obj must be locked with dma_resv_lock(), and * dma_resv_reserve_shared() has been called. * * See also &dma_resv.fence for a discussion of the semantics. */ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence) { struct dma_resv_list *fobj; struct dma_fence *old; unsigned int i, count; dma_fence_get(fence); dma_resv_assert_held(obj); fobj = dma_resv_shared_list(obj); count = fobj->shared_count; write_seqcount_begin(&obj->seq); for (i = 0; i < count; ++i) { old = rcu_dereference_protected(fobj->shared[i], dma_resv_held(obj)); if (old->context == fence->context || dma_fence_is_signaled(old)) goto replace; } BUG_ON(fobj->shared_count >= fobj->shared_max); old = NULL; count++; replace: RCU_INIT_POINTER(fobj->shared[i], fence); /* pointer update must be visible before we extend the shared_count */ smp_store_mb(fobj->shared_count, count); write_seqcount_end(&obj->seq); dma_fence_put(old); } EXPORT_SYMBOL(dma_resv_add_shared_fence); /** * dma_resv_add_excl_fence - Add an exclusive fence. * @obj: the reservation object * @fence: the exclusive fence to add * * Add a fence to the exclusive slot. @obj must be locked with dma_resv_lock(). * Note that this function replaces all fences attached to @obj, see also * &dma_resv.fence_excl for a discussion of the semantics. */ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence) { struct dma_fence *old_fence = dma_resv_excl_fence(obj); struct dma_resv_list *old; u32 i = 0; dma_resv_assert_held(obj); old = dma_resv_shared_list(obj); if (old) i = old->shared_count; dma_fence_get(fence); write_seqcount_begin(&obj->seq); /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(obj->fence_excl, fence); if (old) old->shared_count = 0; write_seqcount_end(&obj->seq); /* inplace update, no shared fences */ while (i--) dma_fence_put(rcu_dereference_protected(old->shared[i], dma_resv_held(obj))); dma_fence_put(old_fence); } EXPORT_SYMBOL(dma_resv_add_excl_fence); /* Restart the iterator by initializing all the necessary fields, but not the * relation to the dma_resv object. */ static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor) { cursor->seq = read_seqcount_begin(&cursor->obj->seq); cursor->index = -1; cursor->shared_count = 0; if (cursor->all_fences) { cursor->fences = dma_resv_shared_list(cursor->obj); if (cursor->fences) cursor->shared_count = cursor->fences->shared_count; } else { cursor->fences = NULL; } cursor->is_restarted = true; } /* Walk to the next not signaled fence and grab a reference to it */ static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor) { struct dma_resv *obj = cursor->obj; do { /* Drop the reference from the previous round */ dma_fence_put(cursor->fence); if (cursor->index == -1) { cursor->fence = dma_resv_excl_fence(obj); cursor->index++; if (!cursor->fence) continue; } else if (!cursor->fences || cursor->index >= cursor->shared_count) { cursor->fence = NULL; break; } else { struct dma_resv_list *fences = cursor->fences; unsigned int idx = cursor->index++; cursor->fence = rcu_dereference(fences->shared[idx]); } cursor->fence = dma_fence_get_rcu(cursor->fence); if (!cursor->fence || !dma_fence_is_signaled(cursor->fence)) break; } while (true); } /** * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj. * @cursor: the cursor with the current position * * Subsequent fences are iterated with dma_resv_iter_next_unlocked(). * * Beware that the iterator can be restarted. Code which accumulates statistics * or similar needs to check for this with dma_resv_iter_is_restarted(). For * this reason prefer the locked dma_resv_iter_first() whenver possible. * * Returns the first fence from an unlocked dma_resv obj. */ struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor) { rcu_read_lock(); do { dma_resv_iter_restart_unlocked(cursor); dma_resv_iter_walk_unlocked(cursor); } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); rcu_read_unlock(); return cursor->fence; } EXPORT_SYMBOL(dma_resv_iter_first_unlocked); /** * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj. * @cursor: the cursor with the current position * * Beware that the iterator can be restarted. Code which accumulates statistics * or similar needs to check for this with dma_resv_iter_is_restarted(). For * this reason prefer the locked dma_resv_iter_next() whenver possible. * * Returns the next fence from an unlocked dma_resv obj. */ struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor) { bool restart; rcu_read_lock(); cursor->is_restarted = false; restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq); do { if (restart) dma_resv_iter_restart_unlocked(cursor); dma_resv_iter_walk_unlocked(cursor); restart = true; } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); rcu_read_unlock(); return cursor->fence; } EXPORT_SYMBOL(dma_resv_iter_next_unlocked); /** * dma_resv_iter_first - first fence from a locked dma_resv object * @cursor: cursor to record the current position * * Subsequent fences are iterated with dma_resv_iter_next_unlocked(). * * Return the first fence in the dma_resv object while holding the * &dma_resv.lock. */ struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor) { struct dma_fence *fence; dma_resv_assert_held(cursor->obj); cursor->index = 0; if (cursor->all_fences) cursor->fences = dma_resv_shared_list(cursor->obj); else cursor->fences = NULL; fence = dma_resv_excl_fence(cursor->obj); if (!fence) fence = dma_resv_iter_next(cursor); cursor->is_restarted = true; return fence; } EXPORT_SYMBOL_GPL(dma_resv_iter_first); /** * dma_resv_iter_next - next fence from a locked dma_resv object * @cursor: cursor to record the current position * * Return the next fences from the dma_resv object while holding the * &dma_resv.lock. */ struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor) { unsigned int idx; dma_resv_assert_held(cursor->obj); cursor->is_restarted = false; if (!cursor->fences || cursor->index >= cursor->fences->shared_count) return NULL; idx = cursor->index++; return rcu_dereference_protected(cursor->fences->shared[idx], dma_resv_held(cursor->obj)); } EXPORT_SYMBOL_GPL(dma_resv_iter_next); /** * dma_resv_copy_fences - Copy all fences from src to dst. * @dst: the destination reservation object * @src: the source reservation object * * Copy all fences from src to dst. dst-lock must be held. */ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src) { struct dma_resv_iter cursor; struct dma_resv_list *list; struct dma_fence *f, *excl; dma_resv_assert_held(dst); list = NULL; excl = NULL; dma_resv_iter_begin(&cursor, src, true); dma_resv_for_each_fence_unlocked(&cursor, f) { if (dma_resv_iter_is_restarted(&cursor)) { dma_resv_list_free(list); dma_fence_put(excl); if (cursor.shared_count) { list = dma_resv_list_alloc(cursor.shared_count); if (!list) { dma_resv_iter_end(&cursor); return -ENOMEM; } list->shared_count = 0; } else { list = NULL; } excl = NULL; } dma_fence_get(f); if (dma_resv_iter_is_exclusive(&cursor)) excl = f; else RCU_INIT_POINTER(list->shared[list->shared_count++], f); } dma_resv_iter_end(&cursor); write_seqcount_begin(&dst->seq); excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst)); list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst)); write_seqcount_end(&dst->seq); dma_resv_list_free(list); dma_fence_put(excl); return 0; } EXPORT_SYMBOL(dma_resv_copy_fences); /** * dma_resv_get_fences - Get an object's shared and exclusive * fences without update side lock held * @obj: the reservation object * @write: true if we should return all fences * @num_fences: the number of fences returned * @fences: the array of fence ptrs returned (array is krealloc'd to the * required size, and must be freed by caller) * * Retrieve all fences from the reservation object. * Returns either zero or -ENOMEM. */ int dma_resv_get_fences(struct dma_resv *obj, bool write, unsigned int *num_fences, struct dma_fence ***fences) { struct dma_resv_iter cursor; struct dma_fence *fence; *num_fences = 0; *fences = NULL; dma_resv_iter_begin(&cursor, obj, write); dma_resv_for_each_fence_unlocked(&cursor, fence) { if (dma_resv_iter_is_restarted(&cursor)) { unsigned int count; while (*num_fences) dma_fence_put((*fences)[--(*num_fences)]); count = cursor.shared_count + 1; /* Eventually re-allocate the array */ *fences = krealloc_array(*fences, count, sizeof(void *), GFP_KERNEL); if (count && !*fences) { dma_resv_iter_end(&cursor); return -ENOMEM; } } (*fences)[(*num_fences)++] = dma_fence_get(fence); } dma_resv_iter_end(&cursor); return 0; } EXPORT_SYMBOL_GPL(dma_resv_get_fences); /** * dma_resv_wait_timeout - Wait on reservation's objects * shared and/or exclusive fences. * @obj: the reservation object * @wait_all: if true, wait on all fences, else wait on just exclusive fence * @intr: if true, do interruptible wait * @timeout: timeout value in jiffies or zero to return immediately * * Callers are not required to hold specific locks, but maybe hold * dma_resv_lock() already * RETURNS * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or * greater than zer on success. */ long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr, unsigned long timeout) { long ret = timeout ? timeout : 1; struct dma_resv_iter cursor; struct dma_fence *fence; dma_resv_iter_begin(&cursor, obj, wait_all); dma_resv_for_each_fence_unlocked(&cursor, fence) { ret = dma_fence_wait_timeout(fence, intr, ret); if (ret <= 0) { dma_resv_iter_end(&cursor); return ret; } } dma_resv_iter_end(&cursor); return ret; } EXPORT_SYMBOL_GPL(dma_resv_wait_timeout); /** * dma_resv_test_signaled - Test if a reservation object's fences have been * signaled. * @obj: the reservation object * @test_all: if true, test all fences, otherwise only test the exclusive * fence * * Callers are not required to hold specific locks, but maybe hold * dma_resv_lock() already. * * RETURNS * * True if all fences signaled, else false. */ bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all) { struct dma_resv_iter cursor; struct dma_fence *fence; dma_resv_iter_begin(&cursor, obj, test_all); dma_resv_for_each_fence_unlocked(&cursor, fence) { dma_resv_iter_end(&cursor); return false; } dma_resv_iter_end(&cursor); return true; } EXPORT_SYMBOL_GPL(dma_resv_test_signaled); /** * dma_resv_describe - Dump description of the resv object into seq_file * @obj: the reservation object * @seq: the seq_file to dump the description into * * Dump a textual description of the fences inside an dma_resv object into the * seq_file. */ void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq) { struct dma_resv_iter cursor; struct dma_fence *fence; dma_resv_for_each_fence(&cursor, obj, true, fence) { seq_printf(seq, "\t%s fence:", dma_resv_iter_is_exclusive(&cursor) ? "Exclusive" : "Shared"); dma_fence_describe(fence, seq); } } EXPORT_SYMBOL_GPL(dma_resv_describe); #if IS_ENABLED(CONFIG_LOCKDEP) static int __init dma_resv_lockdep(void) { struct mm_struct *mm = mm_alloc(); struct ww_acquire_ctx ctx; struct dma_resv obj; struct address_space mapping; int ret; if (!mm) return -ENOMEM; dma_resv_init(&obj); address_space_init_once(&mapping); mmap_read_lock(mm); ww_acquire_init(&ctx, &reservation_ww_class); ret = dma_resv_lock(&obj, &ctx); if (ret == -EDEADLK) dma_resv_lock_slow(&obj, &ctx); fs_reclaim_acquire(GFP_KERNEL); /* for unmap_mapping_range on trylocked buffer objects in shrinkers */ i_mmap_lock_write(&mapping); i_mmap_unlock_write(&mapping); #ifdef CONFIG_MMU_NOTIFIER lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); __dma_fence_might_wait(); lock_map_release(&__mmu_notifier_invalidate_range_start_map); #else __dma_fence_might_wait(); #endif fs_reclaim_release(GFP_KERNEL); ww_mutex_unlock(&obj.lock); ww_acquire_fini(&ctx); mmap_read_unlock(mm); mmput(mm); return 0; } subsys_initcall(dma_resv_lockdep); #endif