libgui: disallow NULL Fence pointers
This change eliminates the uses of a NULL sp<Fence> indicating that no waiting
is required. Instead we use a non-NULL but invalid Fence object for which the
wait methods will return immediately.
Bug: 7892871
Change-Id: I5360aebe3090422ef6920d56c99fc4eedc642e48
diff --git a/libs/ui/Fence.cpp b/libs/ui/Fence.cpp
index a01ac29..b9e0f00 100644
--- a/libs/ui/Fence.cpp
+++ b/libs/ui/Fence.cpp
@@ -29,7 +29,7 @@
namespace android {
-const sp<Fence> Fence::NO_FENCE = sp<Fence>();
+const sp<Fence> Fence::NO_FENCE = sp<Fence>(new Fence);
Fence::Fence() :
mFenceFd(-1) {
@@ -71,7 +71,19 @@
sp<Fence> Fence::merge(const String8& name, const sp<Fence>& f1,
const sp<Fence>& f2) {
ATRACE_CALL();
- int result = sync_merge(name.string(), f1->mFenceFd, f2->mFenceFd);
+ int result;
+ // Merge the two fences. In the case where one of the fences is not a
+ // valid fence (e.g. NO_FENCE) we merge the one valid fence with itself so
+ // that a new fence with the given name is created.
+ if (f1->isValid() && f2->isValid()) {
+ result = sync_merge(name.string(), f1->mFenceFd, f2->mFenceFd);
+ } else if (f1->isValid()) {
+ result = sync_merge(name.string(), f1->mFenceFd, f1->mFenceFd);
+ } else if (f2->isValid()) {
+ result = sync_merge(name.string(), f2->mFenceFd, f2->mFenceFd);
+ } else {
+ return NO_FENCE;
+ }
if (result == -1) {
status_t err = -errno;
ALOGE("merge: sync_merge(\"%s\", %d, %d) returned an error: %s (%d)",
@@ -83,9 +95,6 @@
}
int Fence::dup() const {
- if (mFenceFd == -1) {
- return -1;
- }
return ::dup(mFenceFd);
}
@@ -121,22 +130,24 @@
}
size_t Fence::getFdCount() const {
- return 1;
+ return isValid() ? 1 : 0;
}
status_t Fence::flatten(void* buffer, size_t size, int fds[],
size_t count) const {
- if (size != 0 || count != 1) {
+ if (size != getFlattenedSize() || count != getFdCount()) {
return BAD_VALUE;
}
- fds[0] = mFenceFd;
+ if (isValid()) {
+ fds[0] = mFenceFd;
+ }
return NO_ERROR;
}
status_t Fence::unflatten(void const* buffer, size_t size, int fds[],
size_t count) {
- if (size != 0 || count != 1) {
+ if (size != 0 || (count != 0 && count != 1)) {
return BAD_VALUE;
}
if (mFenceFd != -1) {
@@ -144,7 +155,10 @@
return INVALID_OPERATION;
}
- mFenceFd = fds[0];
+ if (count == 1) {
+ mFenceFd = fds[0];
+ }
+
return NO_ERROR;
}