// 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 <thellstrom-at-vmware-dot-com> */ #include <linux/dma-resv.h> #include <linux/export.h> #include <linux/mm.h> #include <linux/sched/mm.h> #include <linux/mmu_notifier.h> /** * 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. */ 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->lock held. * * 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->lock must be held, and * dma_resv_reserve_shared() has been called. */ 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 shared fence to add * * Add a fence to the exclusive slot. The obj->lock must be held. */ 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; if (fence) 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); /** * 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_list *src_list, *dst_list; struct dma_fence *old, *new; unsigned int i; dma_resv_assert_held(dst); rcu_read_lock(); src_list = dma_resv_shared_list(src); retry: if (src_list) { unsigned int shared_count = src_list->shared_count; rcu_read_unlock(); dst_list = dma_resv_list_alloc(shared_count); if (!dst_list) return -ENOMEM; rcu_read_lock(); src_list = dma_resv_shared_list(src); if (!src_list || src_list->shared_count > shared_count) { kfree(dst_list); goto retry; } dst_list->shared_count = 0; for (i = 0; i < src_list->shared_count; ++i) { struct dma_fence __rcu **dst; struct dma_fence *fence; fence = rcu_dereference(src_list->shared[i]); if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) continue; if (!dma_fence_get_rcu(fence)) { dma_resv_list_free(dst_list); src_list = dma_resv_shared_list(src); goto retry; } if (dma_fence_is_signaled(fence)) { dma_fence_put(fence); continue; } dst = &dst_list->shared[dst_list->shared_count++]; rcu_assign_pointer(*dst, fence); } } else { dst_list = NULL; } new = dma_fence_get_rcu_safe(&src->fence_excl); rcu_read_unlock(); src_list = dma_resv_shared_list(dst); old = dma_resv_excl_fence(dst); write_seqcount_begin(&dst->seq); /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(dst->fence_excl, new); RCU_INIT_POINTER(dst->fence, dst_list); write_seqcount_end(&dst->seq); dma_resv_list_free(src_list); dma_fence_put(old); 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 * @pfence_excl: the returned exclusive fence (or NULL) * @pshared_count: the number of shared fences returned * @pshared: the array of shared fence ptrs returned (array is krealloc'd to * the required size, and must be freed by caller) * * Retrieve all fences from the reservation object. If the pointer for the * exclusive fence is not specified the fence is put into the array of the * shared fences as well. Returns either zero or -ENOMEM. */ int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **pfence_excl, unsigned int *pshared_count, struct dma_fence ***pshared) { struct dma_fence **shared = NULL; struct dma_fence *fence_excl; unsigned int shared_count; int ret = 1; do { struct dma_resv_list *fobj; unsigned int i, seq; size_t sz = 0; shared_count = i = 0; rcu_read_lock(); seq = read_seqcount_begin(&obj->seq); fence_excl = dma_resv_excl_fence(obj); if (fence_excl && !dma_fence_get_rcu(fence_excl)) goto unlock; fobj = dma_resv_shared_list(obj); if (fobj) sz += sizeof(*shared) * fobj->shared_max; if (!pfence_excl && fence_excl) sz += sizeof(*shared); if (sz) { struct dma_fence **nshared; nshared = krealloc(shared, sz, GFP_NOWAIT | __GFP_NOWARN); if (!nshared) { rcu_read_unlock(); dma_fence_put(fence_excl); fence_excl = NULL; nshared = krealloc(shared, sz, GFP_KERNEL); if (nshared) { shared = nshared; continue; } ret = -ENOMEM; break; } shared = nshared; shared_count = fobj ? fobj->shared_count : 0; for (i = 0; i < shared_count; ++i) { shared[i] = rcu_dereference(fobj->shared[i]); if (!dma_fence_get_rcu(shared[i])) break; } } if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) { while (i--) dma_fence_put(shared[i]); dma_fence_put(fence_excl); goto unlock; } ret = 0; unlock: rcu_read_unlock(); } while (ret); if (pfence_excl) *pfence_excl = fence_excl; else if (fence_excl) shared[shared_count++] = fence_excl; if (!shared_count) { kfree(shared); shared = NULL; } *pshared_count = shared_count; *pshared = shared; return ret; } 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; unsigned int seq, shared_count; struct dma_fence *fence; int i; retry: shared_count = 0; seq = read_seqcount_begin(&obj->seq); rcu_read_lock(); i = -1; fence = dma_resv_excl_fence(obj); if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) { if (!dma_fence_get_rcu(fence)) goto unlock_retry; if (dma_fence_is_signaled(fence)) { dma_fence_put(fence); fence = NULL; } } else { fence = NULL; } if (wait_all) { struct dma_resv_list *fobj = dma_resv_shared_list(obj); if (fobj) shared_count = fobj->shared_count; for (i = 0; !fence && i < shared_count; ++i) { struct dma_fence *lfence; lfence = rcu_dereference(fobj->shared[i]); if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) continue; if (!dma_fence_get_rcu(lfence)) goto unlock_retry; if (dma_fence_is_signaled(lfence)) { dma_fence_put(lfence); continue; } fence = lfence; break; } } rcu_read_unlock(); if (fence) { if (read_seqcount_retry(&obj->seq, seq)) { dma_fence_put(fence); goto retry; } ret = dma_fence_wait_timeout(fence, intr, ret); dma_fence_put(fence); if (ret > 0 && wait_all && (i + 1 < shared_count)) goto retry; } return ret; unlock_retry: rcu_read_unlock(); goto retry; } EXPORT_SYMBOL_GPL(dma_resv_wait_timeout); static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence) { struct dma_fence *fence, *lfence = passed_fence; int ret = 1; if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) { fence = dma_fence_get_rcu(lfence); if (!fence) return -1; ret = !!dma_fence_is_signaled(fence); dma_fence_put(fence); } return ret; } /** * 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) { unsigned int seq, shared_count; int ret; rcu_read_lock(); retry: ret = true; shared_count = 0; seq = read_seqcount_begin(&obj->seq); if (test_all) { struct dma_resv_list *fobj = dma_resv_shared_list(obj); unsigned int i; if (fobj) shared_count = fobj->shared_count; for (i = 0; i < shared_count; ++i) { struct dma_fence *fence; fence = rcu_dereference(fobj->shared[i]); ret = dma_resv_test_signaled_single(fence); if (ret < 0) goto retry; else if (!ret) break; } if (read_seqcount_retry(&obj->seq, seq)) goto retry; } if (!shared_count) { struct dma_fence *fence_excl = dma_resv_excl_fence(obj); if (fence_excl) { ret = dma_resv_test_signaled_single(fence_excl); if (ret < 0) goto retry; if (read_seqcount_retry(&obj->seq, seq)) goto retry; } } rcu_read_unlock(); return ret; } EXPORT_SYMBOL_GPL(dma_resv_test_signaled); #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