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-rw-r--r--src/backend/port/win32/signal.c344
1 files changed, 344 insertions, 0 deletions
diff --git a/src/backend/port/win32/signal.c b/src/backend/port/win32/signal.c
new file mode 100644
index 0000000..3218b38
--- /dev/null
+++ b/src/backend/port/win32/signal.c
@@ -0,0 +1,344 @@
+/*-------------------------------------------------------------------------
+ *
+ * signal.c
+ * Microsoft Windows Win32 Signal Emulation Functions
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * src/backend/port/win32/signal.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "libpq/pqsignal.h"
+
+/*
+ * These are exported for use by the UNBLOCKED_SIGNAL_QUEUE() macro.
+ * pg_signal_queue must be volatile since it is changed by the signal
+ * handling thread and inspected without any lock by the main thread.
+ * pg_signal_mask is only changed by main thread so shouldn't need it.
+ */
+volatile int pg_signal_queue;
+int pg_signal_mask;
+
+HANDLE pgwin32_signal_event;
+HANDLE pgwin32_initial_signal_pipe = INVALID_HANDLE_VALUE;
+
+/*
+ * 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;
+
+/* Note that array elements 0 are unused since they correspond to signal 0 */
+static pqsigfunc pg_signal_array[PG_SIGNAL_COUNT];
+static pqsigfunc pg_signal_defaults[PG_SIGNAL_COUNT];
+
+
+/* Signal handling thread functions */
+static DWORD WINAPI pg_signal_thread(LPVOID param);
+static BOOL WINAPI pg_console_handler(DWORD dwCtrlType);
+
+
+/*
+ * pg_usleep --- delay the specified number of microseconds, but
+ * stop waiting if a signal arrives.
+ *
+ * This replaces the non-signal-aware version provided by src/port/pgsleep.c.
+ */
+void
+pg_usleep(long microsec)
+{
+ Assert(pgwin32_signal_event != NULL);
+ 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("could not create signal event: error code %lu", 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("could not create signal handler thread")));
+
+ /* Create console control handle to pick up Ctrl-C etc */
+ if (!SetConsoleCtrlHandler(pg_console_handler, TRUE))
+ ereport(FATAL,
+ (errmsg_internal("could not 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 pqsigsetmask() call.
+ */
+void
+pgwin32_dispatch_queued_signals(void)
+{
+ int exec_mask;
+
+ Assert(pgwin32_signal_event != NULL);
+ EnterCriticalSection(&pg_signal_crit_sec);
+ while ((exec_mask = UNBLOCKED_SIGNAL_QUEUE()) != 0)
+ {
+ /* One or more unblocked signals queued for execution */
+ int i;
+
+ for (i = 1; 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;
+}
+
+
+/*
+ * Unix-like signal handler installation
+ *
+ * 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;
+}
+
+/* Create the signal listener pipe for specified PID */
+HANDLE
+pgwin32_create_signal_listener(pid_t pid)
+{
+ char pipename[128];
+ HANDLE pipe;
+
+ snprintf(pipename, sizeof(pipename), "\\\\.\\pipe\\pgsignal_%u", (int) pid);
+
+ 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)
+ ereport(ERROR,
+ (errmsg("could not create signal listener pipe for PID %d: error code %lu",
+ (int) pid, GetLastError())));
+
+ return pipe;
+}
+
+
+/*
+ * 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!
+ */
+
+
+/*
+ * Queue a signal for the main thread, by setting the flag bit and event.
+ */
+void
+pg_queue_signal(int signum)
+{
+ Assert(pgwin32_signal_event != NULL);
+ if (signum >= PG_SIGNAL_COUNT || signum <= 0)
+ return; /* ignore any bad signal number */
+
+ EnterCriticalSection(&pg_signal_crit_sec);
+ pg_signal_queue |= sigmask(signum);
+ LeaveCriticalSection(&pg_signal_crit_sec);
+
+ SetEvent(pgwin32_signal_event);
+}
+
+/* Signal handling thread */
+static DWORD WINAPI
+pg_signal_thread(LPVOID param)
+{
+ char pipename[128];
+ HANDLE pipe = pgwin32_initial_signal_pipe;
+
+ /* Set up pipe name, in case we have to re-create the pipe. */
+ snprintf(pipename, sizeof(pipename), "\\\\.\\pipe\\pgsignal_%lu", GetCurrentProcessId());
+
+ for (;;)
+ {
+ BOOL fConnected;
+
+ /* Create a new pipe instance if we don't have one. */
+ if (pipe == INVALID_HANDLE_VALUE)
+ {
+ 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)
+ {
+ write_stderr("could not create signal listener pipe: error code %lu; retrying\n", GetLastError());
+ SleepEx(500, FALSE);
+ continue;
+ }
+ }
+
+ /*
+ * Wait for a client to connect. If something connects before we
+ * reach here, we'll get back a "failure" with ERROR_PIPE_CONNECTED,
+ * which is actually a success (way to go, Microsoft).
+ */
+ fConnected = ConnectNamedPipe(pipe, NULL) ? TRUE : (GetLastError() == ERROR_PIPE_CONNECTED);
+ if (fConnected)
+ {
+ /*
+ * We have a connection from a would-be signal sender. Process it.
+ */
+ BYTE sigNum;
+ DWORD bytes;
+
+ if (ReadFile(pipe, &sigNum, 1, &bytes, NULL) &&
+ bytes == 1)
+ {
+ /*
+ * Queue the signal before responding to the client. In this
+ * way, it's guaranteed that once kill() has returned in the
+ * signal sender, the next CHECK_FOR_INTERRUPTS() in the
+ * signal recipient will see the signal. (This is a stronger
+ * guarantee than POSIX makes; maybe we don't need it? But
+ * without it, we've seen timing bugs on Windows that do not
+ * manifest on any known Unix.)
+ */
+ pg_queue_signal(sigNum);
+
+ /*
+ * Write something back to the client, allowing its
+ * CallNamedPipe() call to terminate.
+ */
+ WriteFile(pipe, &sigNum, 1, &bytes, NULL); /* Don't care if it
+ * works or not */
+
+ /*
+ * We must wait for the client to read the data before we can
+ * disconnect, else the data will be lost. (If the WriteFile
+ * call failed, there'll be nothing in the buffer, so this
+ * shouldn't block.)
+ */
+ FlushFileBuffers(pipe);
+ }
+ else
+ {
+ /*
+ * If we fail to read a byte from the client, assume it's the
+ * client's problem and do nothing. Perhaps it'd be better to
+ * force a pipe close and reopen?
+ */
+ }
+
+ /* Disconnect from client so that we can re-use the pipe. */
+ DisconnectNamedPipe(pipe);
+ }
+ else
+ {
+ /*
+ * Connection failed. Cleanup and try again.
+ *
+ * This should never happen. If it does, there's a window where
+ * we'll miss signals until we manage to re-create the pipe.
+ * However, just trying to use the same pipe again is probably not
+ * going to work, so we have little choice.
+ */
+ CloseHandle(pipe);
+ pipe = INVALID_HANDLE_VALUE;
+ }
+ }
+ 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;
+}
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