--- /dev/null
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1995-2002
+ *
+ * Support for concurrent non-blocking I/O and thread waiting.
+ *
+ * ---------------------------------------------------------------------------*/
+
+/* we're outside the realms of POSIX here... */
+/* #include "PosixSource.h" */
+
+#include "Rts.h"
+#include "Schedule.h"
+#include "RtsUtils.h"
+#include "RtsFlags.h"
+#include "Timer.h"
+#include "Itimer.h"
+#include "Signals.h"
+#include "Capability.h"
+#include "posix/Select.h"
+
+# ifdef HAVE_SYS_TYPES_H
+# include <sys/types.h>
+# endif
+
+# ifdef HAVE_SYS_TIME_H
+# include <sys/time.h>
+# endif
+
+#include <errno.h>
+#include <string.h>
+
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+#if !defined(THREADED_RTS)
+/* last timestamp */
+lnat timestamp = 0;
+
+/*
+ * The threaded RTS uses an IO-manager thread in Haskell instead (see GHC.Conc)
+ */
+
+/* There's a clever trick here to avoid problems when the time wraps
+ * around. Since our maximum delay is smaller than 31 bits of ticks
+ * (it's actually 31 bits of microseconds), we can safely check
+ * whether a timer has expired even if our timer will wrap around
+ * before the target is reached, using the following formula:
+ *
+ * (int)((uint)current_time - (uint)target_time) < 0
+ *
+ * if this is true, then our time has expired.
+ * (idea due to Andy Gill).
+ */
+static rtsBool
+wakeUpSleepingThreads(lnat ticks)
+{
+ StgTSO *tso;
+ rtsBool flag = rtsFalse;
+
+ while (sleeping_queue != END_TSO_QUEUE &&
+ (int)(ticks - sleeping_queue->block_info.target) > 0) {
+ tso = sleeping_queue;
+ sleeping_queue = tso->link;
+ tso->why_blocked = NotBlocked;
+ tso->link = END_TSO_QUEUE;
+ IF_DEBUG(scheduler,debugBelch("Waking up sleeping thread %d\n", tso->id));
+ // MainCapability: this code is !THREADED_RTS
+ pushOnRunQueue(&MainCapability,tso);
+ flag = rtsTrue;
+ }
+ return flag;
+}
+
+/* Argument 'wait' says whether to wait for I/O to become available,
+ * or whether to just check and return immediately. If there are
+ * other threads ready to run, we normally do the non-waiting variety,
+ * otherwise we wait (see Schedule.c).
+ *
+ * SMP note: must be called with sched_mutex locked.
+ *
+ * Windows: select only works on sockets, so this doesn't really work,
+ * though it makes things better than before. MsgWaitForMultipleObjects
+ * should really be used, though it only seems to work for read handles,
+ * not write handles.
+ *
+ */
+void
+awaitEvent(rtsBool wait)
+{
+ StgTSO *tso, *prev, *next;
+ rtsBool ready;
+ fd_set rfd,wfd;
+ int numFound;
+ int maxfd = -1;
+ rtsBool select_succeeded = rtsTrue;
+ rtsBool unblock_all = rtsFalse;
+ struct timeval tv;
+ lnat min, ticks;
+
+ tv.tv_sec = 0;
+ tv.tv_usec = 0;
+
+ IF_DEBUG(scheduler,
+ debugBelch("scheduler: checking for threads blocked on I/O");
+ if (wait) {
+ debugBelch(" (waiting)");
+ }
+ debugBelch("\n");
+ );
+
+ /* loop until we've woken up some threads. This loop is needed
+ * because the select timing isn't accurate, we sometimes sleep
+ * for a while but not long enough to wake up a thread in
+ * a threadDelay.
+ */
+ do {
+
+ ticks = timestamp = getourtimeofday();
+ if (wakeUpSleepingThreads(ticks)) {
+ return;
+ }
+
+ if (!wait) {
+ min = 0;
+ } else if (sleeping_queue != END_TSO_QUEUE) {
+ min = (sleeping_queue->block_info.target - ticks)
+ * TICK_MILLISECS * 1000;
+ } else {
+ min = 0x7ffffff;
+ }
+
+ /*
+ * Collect all of the fd's that we're interested in
+ */
+ FD_ZERO(&rfd);
+ FD_ZERO(&wfd);
+
+ for(tso = blocked_queue_hd; tso != END_TSO_QUEUE; tso = next) {
+ next = tso->link;
+
+ switch (tso->why_blocked) {
+ case BlockedOnRead:
+ {
+ int fd = tso->block_info.fd;
+ if (fd >= FD_SETSIZE) {
+ barf("awaitEvent: descriptor out of range");
+ }
+ maxfd = (fd > maxfd) ? fd : maxfd;
+ FD_SET(fd, &rfd);
+ continue;
+ }
+
+ case BlockedOnWrite:
+ {
+ int fd = tso->block_info.fd;
+ if (fd >= FD_SETSIZE) {
+ barf("awaitEvent: descriptor out of range");
+ }
+ maxfd = (fd > maxfd) ? fd : maxfd;
+ FD_SET(fd, &wfd);
+ continue;
+ }
+
+ default:
+ barf("AwaitEvent");
+ }
+ }
+
+ /* Check for any interesting events */
+
+ tv.tv_sec = min / 1000000;
+ tv.tv_usec = min % 1000000;
+
+ while ((numFound = select(maxfd+1, &rfd, &wfd, NULL, &tv)) < 0) {
+ if (errno != EINTR) {
+ /* Handle bad file descriptors by unblocking all the
+ waiting threads. Why? Because a thread might have been
+ a bit naughty and closed a file descriptor while another
+ was blocked waiting. This is less-than-good programming
+ practice, but having the RTS as a result fall over isn't
+ acceptable, so we simply unblock all the waiting threads
+ should we see a bad file descriptor & give the threads
+ a chance to clean up their act.
+
+ Note: assume here that threads becoming unblocked
+ will try to read/write the file descriptor before trying
+ to issue a threadWaitRead/threadWaitWrite again (==> an
+ IOError will result for the thread that's got the bad
+ file descriptor.) Hence, there's no danger of a bad
+ file descriptor being repeatedly select()'ed on, so
+ the RTS won't loop.
+ */
+ if ( errno == EBADF ) {
+ unblock_all = rtsTrue;
+ break;
+ } else {
+ perror("select");
+ barf("select failed");
+ }
+ }
+
+ /* We got a signal; could be one of ours. If so, we need
+ * to start up the signal handler straight away, otherwise
+ * we could block for a long time before the signal is
+ * serviced.
+ */
+#if defined(RTS_USER_SIGNALS)
+ if (signals_pending()) {
+ startSignalHandlers(&MainCapability);
+ return; /* still hold the lock */
+ }
+#endif
+
+ /* we were interrupted, return to the scheduler immediately.
+ */
+ if (sched_state >= SCHED_INTERRUPTING) {
+ return; /* still hold the lock */
+ }
+
+ /* check for threads that need waking up
+ */
+ wakeUpSleepingThreads(getourtimeofday());
+
+ /* If new runnable threads have arrived, stop waiting for
+ * I/O and run them.
+ */
+ if (!emptyRunQueue(&MainCapability)) {
+ return; /* still hold the lock */
+ }
+ }
+
+ /* Step through the waiting queue, unblocking every thread that now has
+ * a file descriptor in a ready state.
+ */
+
+ prev = NULL;
+ if (select_succeeded || unblock_all) {
+ for(tso = blocked_queue_hd; tso != END_TSO_QUEUE; tso = next) {
+ next = tso->link;
+ switch (tso->why_blocked) {
+ case BlockedOnRead:
+ ready = unblock_all || FD_ISSET(tso->block_info.fd, &rfd);
+ break;
+ case BlockedOnWrite:
+ ready = unblock_all || FD_ISSET(tso->block_info.fd, &wfd);
+ break;
+ default:
+ barf("awaitEvent");
+ }
+
+ if (ready) {
+ IF_DEBUG(scheduler,debugBelch("Waking up blocked thread %d\n", tso->id));
+ tso->why_blocked = NotBlocked;
+ tso->link = END_TSO_QUEUE;
+ pushOnRunQueue(&MainCapability,tso);
+ } else {
+ if (prev == NULL)
+ blocked_queue_hd = tso;
+ else
+ prev->link = tso;
+ prev = tso;
+ }
+ }
+
+ if (prev == NULL)
+ blocked_queue_hd = blocked_queue_tl = END_TSO_QUEUE;
+ else {
+ prev->link = END_TSO_QUEUE;
+ blocked_queue_tl = prev;
+ }
+ }
+
+ } while (wait && sched_state == SCHED_RUNNING
+ && emptyRunQueue(&MainCapability));
+}
+
+#endif /* THREADED_RTS */
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