adb: win32: fix shutdown deadlock
adb can hang at shutdown due to a deadlock relating to WSACleanup().
This works around the issue by not calling WSACleanup() which shouldn't
be done anyway since threads aren't done using Winsock at shutdown.
A quick way to reproduce the original problem is to run many instances
of adb, many of which will call exit() soon:
for /l %i in (1,1,20) do @start adb nodaemon server
You may have to boost the 20 to 200, or set ADB_TRACE=1 or use Windows
10 instead of Windows 7, to affect the timing, but eventually there
should be hung adb processes with that repro.
A more complete fix to prevent problems like this from occuring in the
future, would be to additionally do the following:
- Investigate all static destructors that are called when exit() is
called.
- If they don't do anything important, switch all calls to exit() to
instead call _exit() and then ban exit() from being called.
Change-Id: Id1be3bf0053809a45f2eca4461e4c35b5ef9388d
Signed-off-by: Spencer Low <CompareAndSwap@gmail.com>
diff --git a/adb/sysdeps_win32.cpp b/adb/sysdeps_win32.cpp
index db552a2..f525713 100644
--- a/adb/sysdeps_win32.cpp
+++ b/adb/sysdeps_win32.cpp
@@ -652,20 +652,10 @@
static int _winsock_init;
static void
-_cleanup_winsock( void )
-{
- // TODO: WSAStartup() might be called multiple times and this won't properly
- // cleanup the right number of times. Plus, WSACleanup() probably doesn't
- // make sense since it might interrupt other threads using Winsock (since
- // our various threads are not explicitly cleanly shutdown at process exit).
- WSACleanup();
-}
-
-static void
_init_winsock( void )
{
// TODO: Multiple threads calling this may potentially cause multiple calls
- // to WSAStartup() and multiple atexit() calls.
+ // to WSAStartup() which offers no real benefit.
if (!_winsock_init) {
WSADATA wsaData;
int rc = WSAStartup( MAKEWORD(2,2), &wsaData);
@@ -673,8 +663,21 @@
fatal( "adb: could not initialize Winsock: %s",
SystemErrorCodeToString( rc ).c_str());
}
- atexit( _cleanup_winsock );
_winsock_init = 1;
+
+ // Note that we do not call atexit() to register WSACleanup to be called
+ // at normal process termination because:
+ // 1) When exit() is called, there are still threads actively using
+ // Winsock because we don't cleanly shutdown all threads, so it
+ // doesn't make sense to call WSACleanup() and may cause problems
+ // with those threads.
+ // 2) A deadlock can occur when exit() holds a C Runtime lock, then it
+ // calls WSACleanup() which tries to unload a DLL, which tries to
+ // grab the LoaderLock. This conflicts with the device_poll_thread
+ // which holds the LoaderLock because AdbWinApi.dll calls
+ // setupapi.dll which tries to load wintrust.dll which tries to load
+ // crypt32.dll which calls atexit() which tries to acquire the C
+ // Runtime lock that the other thread holds.
}
}
