Here's an attempt at new socket and signal code for win32.

It works on the principle of turning sockets into non-blocking, and then
emulate blocking behaviour on top of that, while allowing signals to
run. Signals are now implemented using an event instead of APCs, thus
getting rid of the issue of APCs not being compatible with "old style"
sockets functions.

It also moves the win32 specific code away from pqsignal.h/c into
port/win32, and also removes the "thread style workaround" of the APC
issue previously in place.

In order to make things work, a few things are also changed in pgstat.c:

1) There is now a separate pipe to the collector and the bufferer. This
is required because the pipe will otherwise only be signalled in one of
the processes when the postmaster goes down. The MS winsock code for
select() must have some kind of workaround for this behaviour, but I
have found no stable way of doing that. You really are not supposed to
use the same socket from more than one process (unless you use
WSADuplicateSocket(), in which case the docs specifically say that only
one will be flagged).

2) The check for "postmaster death" is moved into a separate select()
call after the main loop. The previous behaviour select():ed on the
postmaster pipe, while later explicitly saying "we do NOT check for
postmaster exit inside the loop".
The issue was that the code relies on the same select() call seeing both
the postmaster pipe *and* the pgstat pipe go away. This does not always
happen, and it appears that useing WSAEventSelect() makes it even more
common that it does not.
Since it's only called when the process exits, I don't think using a
separate select() call will have any significant impact on how the stats
collector works.

Magnus Hagander

1 files changed, 300 insertions, 0 deletions

diff --git a/src/backend/port/win32/signal.c b/src/backend/port/win32/signal.c
new file mode 100644
index 00000000000..280f10da23d
--- /dev/null
+++ b/src/backend/port/win32/signal.c
@@ -0,0 +1,300 @@
+/*-------------------------------------------------------------------------
+ *
+ * signal.c
+ *	  Microsoft Windows Win32 Signal Emulation Functions
+ *
+ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL: pgsql/src/backend/port/win32/signal.c,v 1.1 2004/04/12 16:19:18 momjian Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <libpq/pqsignal.h>
+
+
+/* pg_signal_crit_sec is used to protect only pg_signal_queue. That is the only
+ * variable that can be accessed from the signal sending threads! */
+static CRITICAL_SECTION pg_signal_crit_sec;
+static int	pg_signal_queue;
+
+#define PG_SIGNAL_COUNT 32
+static pqsigfunc pg_signal_array[PG_SIGNAL_COUNT];
+static pqsigfunc pg_signal_defaults[PG_SIGNAL_COUNT];
+static int	pg_signal_mask;
+
+DLLIMPORT HANDLE pgwin32_signal_event;
+
+
+/* Signal handling thread function */
+static DWORD WINAPI pg_signal_thread(LPVOID param);
+static BOOL WINAPI pg_console_handler(DWORD dwCtrlType);
+
+/* Sleep function that can be interrupted by signals */
+void pgwin32_backend_usleep(long microsec) {
+	if (WaitForSingleObject(pgwin32_signal_event, (microsec < 500 ? 1 : (microsec + 500) / 1000)) == WAIT_OBJECT_0) {
+		pgwin32_dispatch_queued_signals();
+		errno = EINTR;
+		return;
+	}
+}
+
+
+/* Initialization */
+void
+pgwin32_signal_initialize(void)
+{
+	int			i;
+	HANDLE		signal_thread_handle;
+
+	InitializeCriticalSection(&pg_signal_crit_sec);
+
+	for (i = 0; i < PG_SIGNAL_COUNT; i++)
+	{
+		pg_signal_array[i] = SIG_DFL;
+		pg_signal_defaults[i] = SIG_IGN;
+	}
+	pg_signal_mask = 0;
+	pg_signal_queue = 0;
+
+	/* Create the global event handle used to flag signals */
+	pgwin32_signal_event = CreateEvent(NULL, TRUE, FALSE, NULL);
+	if (pgwin32_signal_event == NULL) 
+		ereport(FATAL,
+				(errmsg_internal("Failed to create signal event: %i!",(int)GetLastError())));
+
+	/* Create thread for handling signals */
+	signal_thread_handle = CreateThread(NULL, 0, pg_signal_thread, NULL, 0, NULL);
+	if (signal_thread_handle == NULL)
+		ereport(FATAL,
+				(errmsg_internal("Failed to create signal handler thread!")));
+
+	/* Create console control handle to pick up Ctrl-C etc */
+	if (!SetConsoleCtrlHandler(pg_console_handler, TRUE)) 
+		ereport(FATAL,
+				(errmsg_internal("Failed to set console control handler!")));
+}
+
+
+/* Dispatch all signals currently queued and not blocked
+ * Blocked signals are ignored, and will be fired at the time of
+ * the sigsetmask() call. */
+void
+pgwin32_dispatch_queued_signals(void)
+{
+	int			i;
+
+	EnterCriticalSection(&pg_signal_crit_sec);
+	while (pg_signal_queue & ~pg_signal_mask)
+	{
+		/* One or more unblocked signals queued for execution */
+
+		int			exec_mask = pg_signal_queue & ~pg_signal_mask;
+
+		for (i = 0; i < PG_SIGNAL_COUNT; i++)
+		{
+			if (exec_mask & sigmask(i))
+			{
+				/* Execute this signal */
+				pqsigfunc	sig = pg_signal_array[i];
+
+				if (sig == SIG_DFL)
+					sig = pg_signal_defaults[i];
+				pg_signal_queue &= ~sigmask(i);
+				if (sig != SIG_ERR && sig != SIG_IGN && sig != SIG_DFL)
+				{
+					LeaveCriticalSection(&pg_signal_crit_sec);
+					sig(i);
+					EnterCriticalSection(&pg_signal_crit_sec);
+					break;		/* Restart outer loop, in case signal mask
+								 * or queue has been modified inside
+								 * signal handler */
+				}
+			}
+		}
+	}
+	ResetEvent(pgwin32_signal_event);
+	LeaveCriticalSection(&pg_signal_crit_sec);
+}
+
+/* signal masking. Only called on main thread, no sync required */
+int
+pqsigsetmask(int mask)
+{
+	int			prevmask;
+
+	prevmask = pg_signal_mask;
+	pg_signal_mask = mask;
+
+	/*
+	 * Dispatch any signals queued up right away, in case we have
+	 * unblocked one or more signals previously queued
+	 */
+	pgwin32_dispatch_queued_signals();
+
+	return prevmask;
+}
+
+
+/* signal manipulation. Only called on main thread, no sync required */
+pqsigfunc
+pqsignal(int signum, pqsigfunc handler)
+{
+	pqsigfunc	prevfunc;
+
+	if (signum >= PG_SIGNAL_COUNT || signum < 0)
+		return SIG_ERR;
+	prevfunc = pg_signal_array[signum];
+	pg_signal_array[signum] = handler;
+	return prevfunc;
+}
+
+/* signal sending */
+int
+pqkill(int pid, int sig)
+{
+	char		pipename[128];
+	BYTE		sigData = sig;
+	BYTE		sigRet = 0;
+	DWORD		bytes;
+
+	if (sig >= PG_SIGNAL_COUNT || sig <= 0)
+	{
+		errno = EINVAL;
+		return -1;
+	}
+	if (pid <= 0)
+	{
+		/* No support for process groups */
+		errno = EINVAL;
+		return -1;
+	}
+	wsprintf(pipename, "\\\\.\\pipe\\pgsignal_%i", 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)
+	{
+		errno = ESRCH;
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * All functions below execute on the signal handler thread
+ * and must be synchronized as such!
+ * NOTE! The only global variable that can be used is
+ * pg_signal_queue!
+ */
+
+
+void
+pg_queue_signal(int signum)
+{
+	if (signum >= PG_SIGNAL_COUNT || signum < 0)
+		return;
+
+	EnterCriticalSection(&pg_signal_crit_sec);
+	pg_signal_queue |= sigmask(signum);
+	LeaveCriticalSection(&pg_signal_crit_sec);
+
+	SetEvent(pgwin32_signal_event);
+}
+
+/* Signal dispatching thread */
+static DWORD WINAPI
+pg_signal_dispatch_thread(LPVOID param)
+{
+	HANDLE		pipe = (HANDLE) param;
+	BYTE		sigNum;
+	DWORD		bytes;
+
+	if (!ReadFile(pipe, &sigNum, 1, &bytes, NULL))
+	{
+		/* Client died before sending */
+		CloseHandle(pipe);
+		return 0;
+	}
+	if (bytes != 1)
+	{
+		/* Received <bytes> bytes over signal pipe (should be 1) */
+		CloseHandle(pipe);
+		return 0;
+	}
+	WriteFile(pipe, &sigNum, 1, &bytes, NULL);	/* Don't care if it works
+												 * or not.. */
+	FlushFileBuffers(pipe);
+	DisconnectNamedPipe(pipe);
+	CloseHandle(pipe);
+
+	pg_queue_signal(sigNum);
+	return 0;
+}
+
+/* Signal handling thread */
+static DWORD WINAPI
+pg_signal_thread(LPVOID param)
+{
+	char		pipename[128];
+	HANDLE		pipe = INVALID_HANDLE_VALUE;
+
+	wsprintf(pipename, "\\\\.\\pipe\\pgsignal_%i", GetCurrentProcessId());
+
+	for (;;)
+	{
+		BOOL		fConnected;
+		HANDLE		hThread;
+
+		pipe = CreateNamedPipe(pipename, PIPE_ACCESS_DUPLEX,
+				   PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
+						   PIPE_UNLIMITED_INSTANCES, 16, 16, 1000, NULL);
+		if (pipe == INVALID_HANDLE_VALUE)
+		{
+			fprintf(stderr, gettext("Failed to create signal listener pipe: %i. Retrying.\n"), (int) GetLastError());
+			SleepEx(500, FALSE);
+			continue;
+		}
+
+		fConnected = ConnectNamedPipe(pipe, NULL) ? TRUE : (GetLastError() == ERROR_PIPE_CONNECTED);
+		if (fConnected)
+		{
+			hThread = CreateThread(NULL, 0,
+					  (LPTHREAD_START_ROUTINE) pg_signal_dispatch_thread,
+								   (LPVOID) pipe, 0, NULL);
+			if (hThread == INVALID_HANDLE_VALUE)
+				fprintf(stderr, gettext("Failed to create signal dispatch thread: %i\n"), (int) GetLastError());
+			else
+				CloseHandle(hThread);
+		}
+		else
+			/* Connection failed. Cleanup and try again */
+			CloseHandle(pipe);
+	}
+	return 0;
+}
+
+
+/* Console control handler will execute on a thread created 
+   by the OS at the time of invocation */
+static BOOL WINAPI pg_console_handler(DWORD dwCtrlType) {
+	if (dwCtrlType == CTRL_C_EVENT ||
+		dwCtrlType == CTRL_BREAK_EVENT ||
+		dwCtrlType == CTRL_CLOSE_EVENT ||
+		dwCtrlType == CTRL_SHUTDOWN_EVENT) {
+		pg_queue_signal(SIGINT);
+		return TRUE;
+	}
+	return FALSE;
+}