Merge "liblog: don't retry opening /dev/pmsg0 if open() fails"
diff --git a/liblog/pmsg_writer.cpp b/liblog/pmsg_writer.cpp
index 8e676bd..037a72c 100644
--- a/liblog/pmsg_writer.cpp
+++ b/liblog/pmsg_writer.cpp
@@ -31,24 +31,32 @@
static atomic_int pmsg_fd;
-// pmsg_fd should only beopened once. If we see that pmsg_fd is uninitialized, we open "/dev/pmsg0"
-// then attempt to compare/exchange it into pmsg_fd. If the compare/exchange was successful, then
-// that will be the fd used for the duration of the program, otherwise a different thread has
-// already opened and written the fd to the atomic, so close the new fd and return.
static void GetPmsgFd() {
+ // Note if open() fails and returns -1, that value is stored into pmsg_fd as an indication that
+ // pmsg is not available and open() should not be retried.
if (pmsg_fd != 0) {
return;
}
int new_fd = TEMP_FAILURE_RETRY(open("/dev/pmsg0", O_WRONLY | O_CLOEXEC));
- if (new_fd <= 0) {
- return;
+
+ // Unlikely that new_fd is 0, but that is synonymous with our uninitialized value, and we'd prefer
+ // STDIN_FILENO != stdin, so we call open() to get a new fd value in this case.
+ if (new_fd == 0) {
+ new_fd = TEMP_FAILURE_RETRY(open("/dev/pmsg0", O_WRONLY | O_CLOEXEC));
+ close(0);
}
+ // pmsg_fd should only be opened once. If we see that pmsg_fd is uninitialized, we open
+ // "/dev/pmsg0" then attempt to compare/exchange it into pmsg_fd. If the compare/exchange was
+ // successful, then that will be the fd used for the duration of the program, otherwise a
+ // different thread has already opened and written the fd to the atomic, so close the new fd and
+ // return.
int uninitialized_value = 0;
if (!pmsg_fd.compare_exchange_strong(uninitialized_value, new_fd)) {
- close(new_fd);
- return;
+ if (new_fd != -1) {
+ close(new_fd);
+ }
}
}
