Loop calling CallNamedPipe() several times in case it fails,

since it can be transient failures, causing kill() to not
properly send signals.

Original patch from Steve Marshall, modified by me.

diff --git a/src/port/kill.c b/src/port/kill.c
index ea71f75c3e93599f6af2e12e570f540e78e41ef8..1ec5ee5b78391611b6a41f14f9dc202e2c53d315 100644 (file)
--- a/src/port/kill.c
+++ b/src/port/kill.c
@@ -9,7 +9,7 @@
  * signals that the backend can recognize.
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/port/kill.c,v 1.11 2009/01/01 17:24:04 momjian Exp $
+ *   $PostgreSQL: pgsql/src/port/kill.c,v 1.12 2009/02/15 13:58:18 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -25,6 +25,7 @@ pgkill(int pid, int sig)
    BYTE        sigData = sig;
    BYTE        sigRet = 0;
    DWORD       bytes;
+   int         pipe_tries;
 
    /* we allow signal 0 here, but it will be ignored in pg_queue_signal */
    if (sig >= PG_SIGNAL_COUNT || sig < 0)
@@ -39,23 +40,33 @@ pgkill(int pid, int sig)
        return -1;
    }
    snprintf(pipename, sizeof(pipename), "\\\\.\\pipe\\pgsignal_%u", pid);
-   if (!CallNamedPipe(pipename, &sigData, 1, &sigRet, 1, &bytes, 1000))
-   {
-       if (GetLastError() == ERROR_FILE_NOT_FOUND)
-           errno = ESRCH;
-       else if (GetLastError() == ERROR_ACCESS_DENIED)
-           errno = EPERM;
-       else
-           errno = EINVAL;
-       return -1;
-   }
-   if (bytes != 1 || sigRet != sig)
+
+   /*
+    * Writing data to the named pipe can fail for transient reasons.
+    * Therefore, it is useful to retry if it fails.  The maximum number of
+    * calls to make was empirically determined from a 90-hour notification
+    * stress test.
+    */
+   for (pipe_tries = 0; pipe_tries < 3; pipe_tries++)
    {
-       errno = ESRCH;
-       return -1;
+       if (CallNamedPipe(pipename, &sigData, 1, &sigRet, 1, &bytes, 1000))
+       {
+           if (bytes != 1 || sigRet != sig)
+           {
+               errno = ESRCH;
+               return -1;
+           }
+           return 0;
+       }
    }
 
-   return 0;
+   if (GetLastError() == ERROR_FILE_NOT_FOUND)
+       errno = ESRCH;
+   else if (GetLastError() == ERROR_ACCESS_DENIED)
+       errno = EPERM;
+   else
+       errno = EINVAL;
+   return -1;
 }
 
 #endif