Module Name: src
Committed By: riastradh
Date: Sun Dec 19 01:50:25 UTC 2021
Modified Files:
src/sys/external/bsd/drm2/linux: linux_reservation.c
Log Message:
Judiciously insert __insn_barrier into reservation logic.
Nothing is volatile here, so we must handle the barriers ourselves.
Also note where membar_producer is implied.
To generate a diff of this commit:
cvs rdiff -u -r1.22 -r1.23 \
src/sys/external/bsd/drm2/linux/linux_reservation.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/linux/linux_reservation.c
diff -u src/sys/external/bsd/drm2/linux/linux_reservation.c:1.22 src/sys/external/bsd/drm2/linux/linux_reservation.c:1.23
--- src/sys/external/bsd/drm2/linux/linux_reservation.c:1.22 Sun Dec 19 01:50:18 2021
+++ src/sys/external/bsd/drm2/linux/linux_reservation.c Sun Dec 19 01:50:25 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: linux_reservation.c,v 1.22 2021/12/19 01:50:18 riastradh Exp $ */
+/* $NetBSD: linux_reservation.c,v 1.23 2021/12/19 01:50:25 riastradh Exp $ */
/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_reservation.c,v 1.22 2021/12/19 01:50:18 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_reservation.c,v 1.23 2021/12/19 01:50:25 riastradh Exp $");
#include <sys/param.h>
#include <sys/poll.h>
@@ -256,7 +256,7 @@ reservation_object_reserve_shared(struct
prealloc = robj->robj_prealloc;
/* If there's an existing list, check it for space. */
- if (list != NULL) {
+ if (list) {
/* If there's too many already, give up. */
if (list->shared_count == UINT32_MAX)
return -ENOMEM;
@@ -312,6 +312,9 @@ struct reservation_object_write_ticket {
* reservation_object_write_commit to commit the writes.
*
* Caller must have robj locked.
+ *
+ * Implies membar_producer, i.e. store-before-store barrier. Does
+ * NOT serve as an acquire operation, however.
*/
static void
reservation_object_write_begin(struct reservation_object *robj,
@@ -330,6 +333,9 @@ reservation_object_write_begin(struct re
* reservation_object_write_begin that returned ticket.
*
* Caller must have robj locked.
+ *
+ * Implies membar_producer, i.e. store-before-store barrier. Does
+ * NOT serve as a release operation, however.
*/
static void
reservation_object_write_commit(struct reservation_object *robj,
@@ -464,7 +470,7 @@ reservation_object_add_shared_fence(stru
KASSERT(list != NULL);
KASSERT(list->shared_count < list->shared_max);
- /* Begin an update. */
+ /* Begin an update. Implies membar_producer for fence. */
reservation_object_write_begin(robj, &ticket);
/* Find a fence with the same context number. */
@@ -512,7 +518,10 @@ reservation_object_add_shared_fence(stru
if (replace == NULL)
prealloc->shared[prealloc->shared_count++] = fence;
- /* Now ready to replace the list. Begin an update. */
+ /*
+ * Now ready to replace the list. Begin an update.
+ * Implies membar_producer for fence and prealloc.
+ */
reservation_object_write_begin(robj, &ticket);
/* Replace the list. */
@@ -527,7 +536,7 @@ reservation_object_add_shared_fence(stru
* (We are not in a position at this point to sleep
* waiting for activity on all CPUs.)
*/
- if (list != NULL)
+ if (list)
objlist_defer_free(list);
}
@@ -572,7 +581,9 @@ top:
reservation_object_read_begin(robj, &ticket);
/* If there is a shared list, grab it. */
- if ((list = robj->fence) != NULL) {
+ list = robj->fence;
+ __insn_barrier();
+ if (list) {
/* Make sure the content of the list has been published. */
membar_datadep_consumer();
@@ -627,7 +638,9 @@ top:
}
/* If there is an exclusive fence, grab it. */
- if ((fence = robj->fence_excl) != NULL) {
+ fence = robj->fence_excl;
+ __insn_barrier();
+ if (fence) {
/* Make sure the content of the fence has been published. */
membar_datadep_consumer();
}
@@ -707,7 +720,11 @@ top:
reservation_object_read_begin(robj, &ticket);
/* If shared is requested and there is a shared list, test it. */
- if (shared && (list = robj->fence) != NULL) {
+ if (!shared)
+ goto excl;
+ list = robj->fence;
+ __insn_barrier();
+ if (list) {
/* Make sure the content of the list has been published. */
membar_datadep_consumer();
@@ -738,8 +755,11 @@ top:
}
}
+excl:
/* If there is an exclusive fence, test it. */
- if ((fence = robj->fence_excl) != NULL) {
+ fence = robj->fence_excl;
+ __insn_barrier();
+ if (fence) {
/* Make sure the content of the fence has been published. */
membar_datadep_consumer();
@@ -804,7 +824,11 @@ top:
reservation_object_read_begin(robj, &ticket);
/* If shared is requested and there is a shared list, wait on it. */
- if (shared && (list = robj->fence) != NULL) {
+ if (!shared)
+ goto excl;
+ list = robj->fence;
+ __insn_barrier();
+ if (list) {
/* Make sure the content of the list has been published. */
membar_datadep_consumer();
@@ -834,8 +858,11 @@ top:
}
}
+excl:
/* If there is an exclusive fence, test it. */
- if ((fence = robj->fence_excl) != NULL) {
+ fence = robj->fence_excl;
+ __insn_barrier();
+ if (fence) {
/* Make sure the content of the fence has been published. */
membar_datadep_consumer();
@@ -976,7 +1003,11 @@ top:
reservation_object_read_begin(robj, &ticket);
/* If we want to wait for all fences, get the shared list. */
- if ((events & POLLOUT) && (list = robj->fence) != NULL) do {
+ if (!(events & POLLOUT))
+ goto excl;
+ list = robj->fence;
+ __insn_barrier();
+ if (list) do {
/* Make sure the content of the list has been published. */
membar_datadep_consumer();
@@ -1047,8 +1078,11 @@ top:
}
} while (0);
+excl:
/* We always wait for at least the exclusive fence, so get it. */
- if ((fence = robj->fence_excl) != NULL) do {
+ fence = robj->fence_excl;
+ __insn_barrier();
+ if (fence) do {
/* Make sure the content of the fence has been published. */
membar_datadep_consumer();
