Artifact 12cffa5d87341c7b6e08cf465c67df5b6d48368b:

• File win/tclWinSock.c — part of check-in [521b7229c4] at 2014-03-08 00:21:59 on branch win-sock-async-connect-race-fix — socket -async and gets/puts stall on windows (Ticket [336441ed59]) This is a change for a problem which is pretty much impossible to test for in the testsuite, as it is a race condition on a problem with Windows and as such cannot be reliably induced from the Tcl side, script nor C. The problem affects only sockets which are opened -async. At the time of the socket's creation the core will remember this fact in the SocketState flags (SOCKET_ASYNC_CONNECT <SAC>) and in the events to look for with select (FD_CONNECT). Then, to handle the possiblity that the script writes to or read from the socket before the connection has completed the driver functions Tcp(Input|Output)Proc check for the flag, and if it is still set enter WaitForSocketEvent (FD_CONNECT) <WFSE> to sync-wait for the connection before continuing to actually read/write. Unfortunately Windows sometimes deigns to not deliver FD_CONNECT, skipping directly to FD_READ|WRITE. When that happens the unmodified WFSE gets stuck in WFSO, and hangs the entire Tcl process. The core actually already has code to deal with that situation, in part. This code is found in the SOCKET_MESSAGE branch of the big switch in SocketProc(). When it finds <SAC> in the flags not reset by an FD_CONNECT event it unconditionally clears the flag and forces an FD_WRITE on other parts (My change adds a comment to the location in question, as marker). This code works for when Windows delivers the first event before the script manages to read/write from the new socket, because then the driver functions will see the cleared flag and not enter WFSE to wait for FD_CONNECT in the first place. However, if the script was fast enough to already be in the WFSE waiting for FD_CONNECT then the main thread is stuck and the change made by SocketProc() does not help. The commit here fixes that issue by extending WFSE to recognize the reset of SAC by SocketProc() as a valid break condition when it waits for FD_CONNECT, thus preventing it from getting stuck. (user: andreask size: 69326)

A hex dump of this file is not available. Please download the raw binary file and generate a hex dump yourself.