---
drivers/dma-buf/Makefile | 2 +-
drivers/dma-buf/dma-resv-ctx.c | 108 +++++++++++++++++++++++++++++++++
include/linux/dma-resv-ctx.h | 68 +++++++++++++++++++++
include/linux/dma-resv.h | 1 +
4 files changed, 178 insertions(+), 1 deletion(-)
create mode 100644 drivers/dma-buf/dma-resv-ctx.c
create mode 100644 include/linux/dma-resv-ctx.h
diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
index 03479da06422..da7701c85de2 100644
--- a/drivers/dma-buf/Makefile
+++ b/drivers/dma-buf/Makefile
@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0-only
obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \
- dma-resv.o seqno-fence.o
+ dma-resv.o dma-resv-ctx.o seqno-fence.o
obj-$(CONFIG_SYNC_FILE) += sync_file.o
obj-$(CONFIG_SW_SYNC) += sw_sync.o sync_debug.o
obj-$(CONFIG_UDMABUF) += udmabuf.o
diff --git a/drivers/dma-buf/dma-resv-ctx.c b/drivers/dma-buf/dma-resv-ctx.c
new file mode 100644
index 000000000000..cad10fa6f80b
--- /dev/null
+++ b/drivers/dma-buf/dma-resv-ctx.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2019 Advanced Micro Devices, Inc.
+ *
+ * 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, sublicense,
+ * 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 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 NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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:
+ * Christian König <christian.koenig@xxxxxxx>
+ */
+
+#include <linux/dma-resv-ctx.h>
+
+/**
+ * dma_resv_ctx_init - initialize a reservation context
+ * @ctx: the context to initialize
+ *
+ * Start using this reservation context to lock reservation objects for update.
+ */
+void dma_resv_ctx_init(struct dma_resv_ctx *ctx)
+{
+ ww_acquire_init(&ctx->base, &reservation_ww_class);
+ init_llist_head(&ctx->locked);
+ ctx->contended = NULL;
+}
+EXPORT_SYMBOL(dma_resv_ctx_init);
+
+/**
+ * dma_resv_ctx_unlock_all - unlock all reservation objects
+ * @ctx: the context which holds the reservation objects
+ *
+ * Unlocks all reservation objects locked with this context.
+ */
+void dma_resv_ctx_unlock_all(struct dma_resv_ctx *ctx)
+{
+ struct dma_resv *obj, *next;
+
+ if (ctx->contended)
+ dma_resv_unlock(ctx->contended);
+ ctx->contended = NULL;
+
+ llist_for_each_entry_safe(obj, next, ctx->locked.first, locked)
+ ww_mutex_unlock(&obj->lock);
+ init_llist_head(&ctx->locked);
+}
+EXPORT_SYMBOL(dma_resv_ctx_unlock_all);
+
+/**
+ * dma_resv_ctx_lock - lock a reservation object with deadlock handling
+ * @ctx: the context which should be used to lock the object
+ * @obj: the object which needs to be locked
+ * @interruptible: if we should wait interruptible
+ *
+ * Use @ctx to lock the reservation object. If a deadlock is detected we backoff
+ * by releasing all locked objects and use the slow path to lock the reservation
+ * object. After successfully locking in the slow path -EDEADLK is returned to
+ * signal that all other locks must be re-taken as well.
+ */
+int dma_resv_ctx_lock(struct dma_resv_ctx *ctx, struct dma_resv *obj,
+ bool interruptible)
+{
+ int ret = 0;
+
+ if (unlikely(ctx->contended == obj))
+ ctx->contended = NULL;
+ else if (interruptible)
+ ret = dma_resv_lock_interruptible(obj, &ctx->base);
+ else
+ ret = dma_resv_lock(obj, &ctx->base);
+
+ if (likely(!ret)) {
+ /* don't use llist_add here, we have separate locking */
+ obj->locked.next = ctx->locked.first;
+ ctx->locked.first = &obj->locked;
+ return 0;
+ }
+ if (unlikely(ret != -EDEADLK))
+ return ret;
+
+ dma_resv_ctx_unlock_all(ctx);
+
+ if (interruptible) {
+ ret = dma_resv_lock_slow_interruptible(obj, &ctx->base);
+ if (unlikely(ret))
+ return ret;
+ } else {
+ dma_resv_lock_slow(obj, &ctx->base);
+ }
+
+ ctx->contended = obj;
+ return -EDEADLK;
+}
+EXPORT_SYMBOL(dma_resv_ctx_lock);
diff --git a/include/linux/dma-resv-ctx.h b/include/linux/dma-resv-ctx.h
new file mode 100644
index 000000000000..86473de65167
--- /dev/null
+++ b/include/linux/dma-resv-ctx.h
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2019 Advanced Micro Devices, Inc.
+ *
+ * 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, sublicense,
+ * 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 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 NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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:
+ * Christian König <christian.koenig@xxxxxxx>
+ */
+
+#ifndef _LINUX_DMA_RESV_CTX_H
+#define _LINUX_DMA_RESV_CTX_H
+
+#include <linux/llist.h>
+#include <linux/dma-resv.h>
+
+/**
+ * struct dma_resv_ctx - context to lock reservation objects
+ * @base: ww_acquire_ctx used for deadlock detection
+ * @locked: list of dma_resv objects locked in this context
+ * @contended: contended dma_resv object
+ */
+struct dma_resv_ctx {
+ struct ww_acquire_ctx base;
+ struct llist_head locked;
+ struct dma_resv *contended;
+};
+
+/**
+ * dma_resv_ctx_done - wrapper for ww_acquire_done
+ * @ctx: the reservation context which is done with locking
+ */
+static inline void dma_resv_ctx_done(struct dma_resv_ctx *ctx)
+{
+ ww_acquire_done(&ctx->base);
+}
+
+/**
+ * dma_resv_ctx_fini - wrapper for ww_acquire_fini
+ * @ctx: the reservation context which is finished
+ */
+static inline void dma_resv_ctx_fini(struct dma_resv_ctx *ctx)
+{
+ ww_acquire_fini(&ctx->base);
+}
+
+void dma_resv_ctx_init(struct dma_resv_ctx *ctx);
+void dma_resv_ctx_unlock_all(struct dma_resv_ctx *ctx);
+int dma_resv_ctx_lock(struct dma_resv_ctx *ctx, struct dma_resv *obj,
+ bool interruptible);
+
+#endif /* _LINUX_DMA_RESV_CTX_H */
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index ee50d10f052b..1267822c2669 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -71,6 +71,7 @@ struct dma_resv_list {
*/
struct dma_resv {
struct ww_mutex lock;
+ struct llist_node locked;
seqcount_t seq;
struct dma_fence __rcu *fence_excl;
--
2.17.1
