363 lines
9.3 KiB
C
363 lines
9.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* signal.c
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* Microsoft Windows Win32 Signal Emulation Functions
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/backend/port/win32/signal.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "libpq/pqsignal.h"
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/*
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* These are exported for use by the UNBLOCKED_SIGNAL_QUEUE() macro.
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* pg_signal_queue must be volatile since it is changed by the signal
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* handling thread and inspected without any lock by the main thread.
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* pg_signal_mask is only changed by main thread so shouldn't need it.
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*/
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volatile int pg_signal_queue;
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int pg_signal_mask;
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HANDLE pgwin32_signal_event;
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HANDLE pgwin32_initial_signal_pipe = INVALID_HANDLE_VALUE;
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/*
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* pg_signal_crit_sec is used to protect only pg_signal_queue. That is the only
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* variable that can be accessed from the signal sending threads!
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*/
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static CRITICAL_SECTION pg_signal_crit_sec;
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/* Note that array elements 0 are unused since they correspond to signal 0 */
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static pqsigfunc pg_signal_array[PG_SIGNAL_COUNT];
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static pqsigfunc pg_signal_defaults[PG_SIGNAL_COUNT];
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/* Signal handling thread function */
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static DWORD WINAPI pg_signal_thread(LPVOID param);
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static BOOL WINAPI pg_console_handler(DWORD dwCtrlType);
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/*
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* pg_usleep --- delay the specified number of microseconds, but
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* stop waiting if a signal arrives.
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*
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* This replaces the non-signal-aware version provided by src/port/pgsleep.c.
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*/
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void
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pg_usleep(long microsec)
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{
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Assert(pgwin32_signal_event != NULL);
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if (WaitForSingleObject(pgwin32_signal_event,
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(microsec < 500 ? 1 : (microsec + 500) / 1000))
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== WAIT_OBJECT_0)
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{
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pgwin32_dispatch_queued_signals();
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errno = EINTR;
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return;
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}
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}
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/* Initialization */
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void
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pgwin32_signal_initialize(void)
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{
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int i;
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HANDLE signal_thread_handle;
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InitializeCriticalSection(&pg_signal_crit_sec);
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for (i = 0; i < PG_SIGNAL_COUNT; i++)
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{
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pg_signal_array[i] = SIG_DFL;
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pg_signal_defaults[i] = SIG_IGN;
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}
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pg_signal_mask = 0;
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pg_signal_queue = 0;
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/* Create the global event handle used to flag signals */
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pgwin32_signal_event = CreateEvent(NULL, TRUE, FALSE, NULL);
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if (pgwin32_signal_event == NULL)
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ereport(FATAL,
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(errmsg_internal("could not create signal event: error code %lu", GetLastError())));
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/* Create thread for handling signals */
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signal_thread_handle = CreateThread(NULL, 0, pg_signal_thread, NULL, 0, NULL);
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if (signal_thread_handle == NULL)
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ereport(FATAL,
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(errmsg_internal("could not create signal handler thread")));
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/* Create console control handle to pick up Ctrl-C etc */
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if (!SetConsoleCtrlHandler(pg_console_handler, TRUE))
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ereport(FATAL,
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(errmsg_internal("could not set console control handler")));
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}
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/*
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* Dispatch all signals currently queued and not blocked
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* Blocked signals are ignored, and will be fired at the time of
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* the pqsigsetmask() call.
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*/
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void
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pgwin32_dispatch_queued_signals(void)
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{
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int exec_mask;
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Assert(pgwin32_signal_event != NULL);
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EnterCriticalSection(&pg_signal_crit_sec);
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while ((exec_mask = UNBLOCKED_SIGNAL_QUEUE()) != 0)
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{
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/* One or more unblocked signals queued for execution */
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int i;
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for (i = 1; i < PG_SIGNAL_COUNT; i++)
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{
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if (exec_mask & sigmask(i))
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{
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/* Execute this signal */
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pqsigfunc sig = pg_signal_array[i];
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if (sig == SIG_DFL)
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sig = pg_signal_defaults[i];
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pg_signal_queue &= ~sigmask(i);
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if (sig != SIG_ERR && sig != SIG_IGN && sig != SIG_DFL)
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{
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LeaveCriticalSection(&pg_signal_crit_sec);
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sig(i);
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EnterCriticalSection(&pg_signal_crit_sec);
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break; /* Restart outer loop, in case signal mask or
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* queue has been modified inside signal
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* handler */
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}
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}
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}
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}
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ResetEvent(pgwin32_signal_event);
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LeaveCriticalSection(&pg_signal_crit_sec);
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}
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/* signal masking. Only called on main thread, no sync required */
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int
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pqsigsetmask(int mask)
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{
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int prevmask;
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prevmask = pg_signal_mask;
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pg_signal_mask = mask;
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/*
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* Dispatch any signals queued up right away, in case we have unblocked
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* one or more signals previously queued
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*/
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pgwin32_dispatch_queued_signals();
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return prevmask;
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}
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/*
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* Unix-like signal handler installation
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*
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* Only called on main thread, no sync required
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*/
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pqsigfunc
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pqsignal(int signum, pqsigfunc handler)
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{
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pqsigfunc prevfunc;
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if (signum >= PG_SIGNAL_COUNT || signum < 0)
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return SIG_ERR;
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prevfunc = pg_signal_array[signum];
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pg_signal_array[signum] = handler;
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return prevfunc;
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}
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/* Create the signal listener pipe for specified PID */
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HANDLE
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pgwin32_create_signal_listener(pid_t pid)
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{
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char pipename[128];
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HANDLE pipe;
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snprintf(pipename, sizeof(pipename), "\\\\.\\pipe\\pgsignal_%u", (int) pid);
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pipe = CreateNamedPipe(pipename, PIPE_ACCESS_DUPLEX,
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PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
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PIPE_UNLIMITED_INSTANCES, 16, 16, 1000, NULL);
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if (pipe == INVALID_HANDLE_VALUE)
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ereport(ERROR,
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(errmsg("could not create signal listener pipe for PID %d: error code %lu",
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(int) pid, GetLastError())));
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return pipe;
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}
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/*
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* All functions below execute on the signal handler thread
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* and must be synchronized as such!
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* NOTE! The only global variable that can be used is
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* pg_signal_queue!
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*/
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void
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pg_queue_signal(int signum)
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{
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Assert(pgwin32_signal_event != NULL);
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if (signum >= PG_SIGNAL_COUNT || signum <= 0)
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return;
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EnterCriticalSection(&pg_signal_crit_sec);
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pg_signal_queue |= sigmask(signum);
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LeaveCriticalSection(&pg_signal_crit_sec);
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SetEvent(pgwin32_signal_event);
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}
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/* Signal dispatching thread */
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static DWORD WINAPI
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pg_signal_dispatch_thread(LPVOID param)
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{
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HANDLE pipe = (HANDLE) param;
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BYTE sigNum;
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DWORD bytes;
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if (!ReadFile(pipe, &sigNum, 1, &bytes, NULL))
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{
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/* Client died before sending */
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CloseHandle(pipe);
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return 0;
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}
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if (bytes != 1)
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{
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/* Received <bytes> bytes over signal pipe (should be 1) */
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CloseHandle(pipe);
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return 0;
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}
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WriteFile(pipe, &sigNum, 1, &bytes, NULL); /* Don't care if it works or
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* not.. */
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FlushFileBuffers(pipe);
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DisconnectNamedPipe(pipe);
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CloseHandle(pipe);
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pg_queue_signal(sigNum);
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return 0;
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}
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/* Signal handling thread */
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static DWORD WINAPI
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pg_signal_thread(LPVOID param)
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{
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char pipename[128];
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HANDLE pipe = pgwin32_initial_signal_pipe;
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snprintf(pipename, sizeof(pipename), "\\\\.\\pipe\\pgsignal_%lu", GetCurrentProcessId());
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for (;;)
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{
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BOOL fConnected;
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HANDLE hThread;
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if (pipe == INVALID_HANDLE_VALUE)
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{
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pipe = CreateNamedPipe(pipename, PIPE_ACCESS_DUPLEX,
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PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
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PIPE_UNLIMITED_INSTANCES, 16, 16, 1000, NULL);
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if (pipe == INVALID_HANDLE_VALUE)
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{
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write_stderr("could not create signal listener pipe: error code %lu; retrying\n", GetLastError());
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SleepEx(500, FALSE);
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continue;
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}
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}
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fConnected = ConnectNamedPipe(pipe, NULL) ? TRUE : (GetLastError() == ERROR_PIPE_CONNECTED);
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if (fConnected)
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{
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HANDLE newpipe;
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/*
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* We have a connected pipe. Pass this off to a separate thread
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* that will do the actual processing of the pipe.
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*
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* We must also create a new instance of the pipe *before* we
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* start running the new thread. If we don't, there is a race
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* condition whereby the dispatch thread might run CloseHandle()
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* before we have created a new instance, thereby causing a small
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* window of time where we will miss incoming requests.
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*/
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newpipe = CreateNamedPipe(pipename, PIPE_ACCESS_DUPLEX,
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PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
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PIPE_UNLIMITED_INSTANCES, 16, 16, 1000, NULL);
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if (newpipe == INVALID_HANDLE_VALUE)
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{
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/*
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* This really should never fail. Just retry in case it does,
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* even though we have a small race window in that case. There
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* is nothing else we can do other than abort the whole
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* process which will be even worse.
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*/
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write_stderr("could not create signal listener pipe: error code %lu; retrying\n", GetLastError());
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/*
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* Keep going so we at least dispatch this signal. Hopefully,
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* the call will succeed when retried in the loop soon after.
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*/
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}
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hThread = CreateThread(NULL, 0,
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(LPTHREAD_START_ROUTINE) pg_signal_dispatch_thread,
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(LPVOID) pipe, 0, NULL);
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if (hThread == INVALID_HANDLE_VALUE)
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write_stderr("could not create signal dispatch thread: error code %lu\n",
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GetLastError());
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else
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CloseHandle(hThread);
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/*
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* Background thread is running with our instance of the pipe. So
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* replace our reference with the newly created one and loop back
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* up for another run.
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*/
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pipe = newpipe;
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}
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else
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{
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/*
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* Connection failed. Cleanup and try again.
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*
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* This should never happen. If it does, we have a small race
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* condition until we loop up and re-create the pipe.
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*/
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CloseHandle(pipe);
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pipe = INVALID_HANDLE_VALUE;
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}
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}
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return 0;
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}
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/* Console control handler will execute on a thread created
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by the OS at the time of invocation */
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static BOOL WINAPI
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pg_console_handler(DWORD dwCtrlType)
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{
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if (dwCtrlType == CTRL_C_EVENT ||
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dwCtrlType == CTRL_BREAK_EVENT ||
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dwCtrlType == CTRL_CLOSE_EVENT ||
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dwCtrlType == CTRL_SHUTDOWN_EVENT)
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{
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pg_queue_signal(SIGINT);
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return TRUE;
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}
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return FALSE;
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}
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