/* This curious flag is provided for the benefit of the Haskell binding
* to POSIX.1 to control whether or not to include SA_NOCLDSTOP when
* installing a SIGCHLD handler.
- *
*/
StgInt nocldstop = 0;
+/* -----------------------------------------------------------------------------
+ * The table of signal handlers
+ * -------------------------------------------------------------------------- */
+
#if defined(RTS_USER_SIGNALS)
/* SUP: The type of handlers is a little bit, well, doubtful... */
static nat n_haskell_handlers = 0;
-#define N_PENDING_HANDLERS 16
-
-StgPtr pending_handler_buf[N_PENDING_HANDLERS];
-StgPtr *next_pending_handler = pending_handler_buf;
-
-/* -----------------------------------------------------------------------------
- * Signal handling
- * -------------------------------------------------------------------------- */
-
-#ifdef RTS_SUPPORTS_THREADS
-pthread_t signalHandlingThread;
-#endif
-
-// Handle all signals in the current thread.
-// Called from Capability.c whenever the main capability is granted to a thread
-// and in installDefaultHandlers
-void
-handleSignalsInThisThread(void)
-{
-#ifdef RTS_SUPPORTS_THREADS
- signalHandlingThread = pthread_self();
-#endif
-}
-
/* -----------------------------------------------------------------------------
* Allocate/resize the table of signal handlers.
* -------------------------------------------------------------------------- */
}
/* -----------------------------------------------------------------------------
+ * Pending Handlers
+ *
+ * The mechanism for starting handlers differs between the threaded
+ * (RTS_SUPPORTS_THREADS) and non-threaded versions of the RTS.
+ *
+ * When the RTS is single-threaded, we just write the pending signal
+ * handlers into a buffer, and start a thread for each one in the
+ * scheduler loop.
+ *
+ * When RTS_SUPPORTS_THREADS, the problem is that signals might be
+ * delivered to multiple threads, so we would need to synchronise
+ * access to pending_handler_buf somehow. Using thread
+ * synchronisation from a signal handler isn't possible in general
+ * (some OSs support it, eg. MacOS X, but not all). So instead:
+ *
+ * - the signal handler writes the signal number into the pipe
+ * managed by the IO manager thread (see GHC.Conc).
+ * - the IO manager picks up the signal number and calls
+ * startSignalHandler() to start the thread.
+ *
+ * This also has the nice property that we don't need to arrange to
+ * wake up a worker task to start the signal handler: the IO manager
+ * wakes up when we write into the pipe.
+ *
+ * -------------------------------------------------------------------------- */
+
+// Here's the pipe into which we will send our signals
+static int io_manager_pipe = -1;
+
+void
+setIOManagerPipe (int fd)
+{
+ // only called when RTS_SUPPORTS_THREADS, but unconditionally
+ // compiled here because GHC.Conc depends on it.
+ io_manager_pipe = fd;
+}
+
+#if !defined(RTS_SUPPORTS_THREADS)
+
+#define N_PENDING_HANDLERS 16
+
+StgPtr pending_handler_buf[N_PENDING_HANDLERS];
+StgPtr *next_pending_handler = pending_handler_buf;
+
+#endif /* RTS_SUPPORTS_THREADS */
+
+/* -----------------------------------------------------------------------------
* SIGCONT handler
*
* It seems that shells tend to put stdin back into blocking mode
{
sigset_t signals;
-#if defined(THREADED_RTS)
- // Make the thread that currently holds the main capability
- // handle the signal.
- // This makes sure that awaitEvent() is interrupted
- // and it (hopefully) prevents race conditions
- // (signal handlers are not atomic with respect to other threads)
+#if defined(RTS_SUPPORTS_THREADS)
- if(pthread_self() != signalHandlingThread) {
- pthread_kill(signalHandlingThread, sig);
- return;
+ if (io_manager_pipe != -1)
+ {
+ // Write the signal number into the pipe as a single byte. We
+ // hope that signals fit into a byte...
+ StgWord8 csig = (StgWord8)sig;
+ write(io_manager_pipe, &csig, 1);
}
-#endif
+ // If the IO manager hasn't told us what the FD of the write end
+ // of its pipe is, there's not much we can do here, so just ignore
+ // the signal..
+
+#else /* not RTS_SUPPORTS_THREADS */
/* Can't call allocate from here. Probably can't call malloc
either. However, we have to schedule a new thread somehow.
stg_exit(EXIT_FAILURE);
}
+#endif /* RTS_SUPPORTS_THREADS */
+
// re-establish the signal handler, and carry on
sigemptyset(&signals);
sigaddset(&signals, sig);
return n_haskell_handlers != 0;
}
+#if !defined(RTS_SUPPORTS_THREADS)
void
awaitUserSignals(void)
{
pause();
}
}
+#endif
/* -----------------------------------------------------------------------------
* Install a Haskell signal handler.
}
/* -----------------------------------------------------------------------------
- * Creating new threads for the pending signal handlers.
+ * Creating new threads for signal handlers.
* -------------------------------------------------------------------------- */
+
+void
+startSignalHandler(int sig) // called by the IO manager, see GHC.Conc
+{
+#if defined(RTS_SUPPORTS_THREADS)
+ // ToDo: fix race window between the time at which the signal is
+ // delivered and the deRefStablePtr() call here. There's no way
+ // to safely uninstall a signal handler.
+ scheduleThread(
+ createIOThread(RtsFlags.GcFlags.initialStkSize,
+ (StgClosure *)deRefStablePtr((StgStablePtr)handlers[sig]))
+ );
+#endif
+}
+
void
startSignalHandlers(void)
{
+#if !defined(RTS_SUPPORTS_THREADS)
blockUserSignals();
while (next_pending_handler != pending_handler_buf) {
}
unblockUserSignals();
+#endif
}
/* ----------------------------------------------------------------------------
* avoid race conditions.
* -------------------------------------------------------------------------- */
+#if !defined(RTS_SUPPORTS_THREADS)
void
markSignalHandlers (evac_fn evac)
{
evac((StgClosure **)p);
}
}
+#else
+void
+markSignalHandlers (evac_fn evac STG_UNUSED)
+{
+}
+#endif
#else /* !RTS_USER_SIGNALS */
StgInt
pthread_kill(startup_guy, sig);
return;
}
- // ToDo: The code for the threaded RTS below does something very
- // similar. Maybe the SMP special case is not needed
- // -- Wolfgang Thaller
-#elif defined(THREADED_RTS)
- // Make the thread that currently holds the main capability
- // handle the signal.
- // This makes sure that awaitEvent() is interrupted
- if(pthread_self() != signalHandlingThread) {
- pthread_kill(signalHandlingThread, sig);
- return;
- }
#endif
// If we're already trying to interrupt the RTS, terminate with
#ifdef SMP
startup_guy = pthread_self();
#endif
-#ifdef RTS_SUPPORTS_THREADS
- handleSignalsInThisThread();
-#endif
// install the SIGINT handler
action.sa_handler = shutdown_handler;
projects / ghc-hetmet.git / commitdiff