dumpstate: set backlog to zero

Set backlog to 0 to make sure that queue size will be minimum.
In Linux, because the minimum queue will be 1, connect() will be blocked
if the other clients already called connect() and the connection request
was not accepted.

Bug: 123306389
Bug: 135575100
Test: execute bugreport in parallel

Change-Id: Iee94de88deb82746818b729387ed9cd39e9b2f99
Signed-off-by: Kansho Nishida <kansho@google.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/cmds/dumpstate/utils.cpp b/cmds/dumpstate/utils.cpp
index 4cbf5776d3..e08c80627c 100644
--- a/cmds/dumpstate/utils.cpp
+++ b/cmds/dumpstate/utils.cpp
@@ -725,7 +725,11 @@ int open_socket(const char *service) {
         return -1;
     }
     fcntl(s, F_SETFD, FD_CLOEXEC);
-    if (listen(s, 4) < 0) {
+
+    // Set backlog to 0 to make sure that queue size will be minimum.
+    // In Linux, because the minimum queue will be 1, connect() will be blocked
+    // if the other clients already called connect() and the connection request was not accepted.
+    if (listen(s, 0) < 0) {
         MYLOGE("listen(control socket): %s\n", strerror(errno));
         return -1;
     }
@@ -736,6 +740,9 @@ int open_socket(const char *service) {
 
     // Close socket just after accept(), to make sure that connect() by client will get error
     // when the socket is used by the other services.
+    // There is still a race condition possibility between accept and close, but there is no way
+    // to close-on-accept atomically.
+    // See detail; b/123306389#comment25
     close(s);
 
     if (fd < 0) {