Module Name: src
Committed By: riastradh
Date: Sun Dec 19 01:15:28 UTC 2021
Modified Files:
src/sys/external/bsd/drm2/include/linux: dma-fence.h
src/sys/external/bsd/drm2/linux: linux_dma_fence.c
Log Message:
Add dma_fence_get_rcu_safe.
To generate a diff of this commit:
cvs rdiff -u -r1.2 -r1.3 src/sys/external/bsd/drm2/include/linux/dma-fence.h
cvs rdiff -u -r1.2 -r1.3 src/sys/external/bsd/drm2/linux/linux_dma_fence.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/external/bsd/drm2/include/linux/dma-fence.h
diff -u src/sys/external/bsd/drm2/include/linux/dma-fence.h:1.2 src/sys/external/bsd/drm2/include/linux/dma-fence.h:1.3
--- src/sys/external/bsd/drm2/include/linux/dma-fence.h:1.2 Sun Dec 19 00:27:17 2021
+++ src/sys/external/bsd/drm2/include/linux/dma-fence.h Sun Dec 19 01:15:28 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: dma-fence.h,v 1.2 2021/12/19 00:27:17 riastradh Exp $ */
+/* $NetBSD: dma-fence.h,v 1.3 2021/12/19 01:15:28 riastradh Exp $ */
/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -112,6 +112,8 @@ struct dma_fence *
dma_fence_get(struct dma_fence *);
struct dma_fence *
dma_fence_get_rcu(struct dma_fence *);
+struct dma_fence *
+ dma_fence_get_rcu_safe(struct dma_fence **);
void dma_fence_put(struct dma_fence *);
int dma_fence_add_callback(struct dma_fence *, struct dma_fence_cb *,
Index: src/sys/external/bsd/drm2/linux/linux_dma_fence.c
diff -u src/sys/external/bsd/drm2/linux/linux_dma_fence.c:1.2 src/sys/external/bsd/drm2/linux/linux_dma_fence.c:1.3
--- src/sys/external/bsd/drm2/linux/linux_dma_fence.c:1.2 Sun Dec 19 00:27:17 2021
+++ src/sys/external/bsd/drm2/linux/linux_dma_fence.c Sun Dec 19 01:15:28 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: linux_dma_fence.c,v 1.2 2021/12/19 00:27:17 riastradh Exp $ */
+/* $NetBSD: linux_dma_fence.c,v 1.3 2021/12/19 01:15:28 riastradh Exp $ */
/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_dma_fence.c,v 1.2 2021/12/19 00:27:17 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_dma_fence.c,v 1.3 2021/12/19 01:15:28 riastradh Exp $");
#include <sys/atomic.h>
#include <sys/condvar.h>
@@ -201,6 +201,52 @@ dma_fence_get_rcu(struct dma_fence *fenc
return fence;
}
+/*
+ * dma_fence_get_rcu_safe(fencep)
+ *
+ * Attempt to acquire a reference to the fence *fencep, which may
+ * be about to be destroyed, during a read section. If the value
+ * of *fencep changes after we read *fencep but before we
+ * increment its reference count, retry. Return *fencep on
+ * success, or NULL on failure.
+ */
+struct dma_fence *
+dma_fence_get_rcu_safe(struct dma_fence **fencep)
+{
+ struct dma_fence *fence, *fence0;
+
+retry:
+ fence = *fencep;
+
+ /* Load fence only once. */
+ __insn_barrier();
+
+ /* If there's nothing there, give up. */
+ if (fence == NULL)
+ return NULL;
+
+ /* Make sure we don't load stale fence guts. */
+ membar_datadep_consumer();
+
+ /* Try to acquire a reference. If we can't, try again. */
+ if (!dma_fence_get_rcu(fence))
+ goto retry;
+
+ /*
+ * Confirm that it's still the same fence. If not, release it
+ * and retry.
+ */
+ fence0 = *fencep;
+ __insn_barrier();
+ if (fence != fence0) {
+ dma_fence_put(fence);
+ goto retry;
+ }
+
+ /* Success! */
+ return fence;
+}
+
static void
dma_fence_release(struct kref *refcount)
{
