--- /dev/null
+/* -----------------------------------------------------------------------------
+ * $Id: Select.c,v 1.1 1999/08/25 16:37:42 simonmar Exp $
+ *
+ * (c) The GHC Team 1995-1999
+ *
+ * Support for concurrent non-blocking I/O and thread waiting.
+ *
+ * ---------------------------------------------------------------------------*/
+
+/* we're outside the realms of POSIX here... */
+#define NON_POSIX_SOURCE
+
+#include "Rts.h"
+#include "Schedule.h"
+#include "RtsUtils.h"
+#include "RtsFlags.h"
+#include "Itimer.h"
+
+# if defined(HAVE_SYS_TYPES_H)
+# include <sys/types.h>
+# endif
+
+# ifdef HAVE_SYS_TIME_H
+# include <sys/time.h>
+# endif
+
+nat ticks_since_select = 0;
+
+/* 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).
+ */
+void
+awaitEvent(rtsBool wait)
+{
+ StgTSO *tso, *prev, *next;
+ rtsBool ready;
+ fd_set rfd,wfd;
+ int min, numFound, delta;
+ int maxfd = -1;
+
+ struct timeval tv,tv_before,tv_after;
+
+ IF_DEBUG(scheduler,belch("Checking for threads blocked on I/O...\n"));
+
+ /* see how long it's been since we last checked the blocked queue.
+ * ToDo: make this check atomic, so we don't lose any ticks.
+ */
+ delta = ticks_since_select;
+ ticks_since_select = 0;
+ delta = delta * TICK_MILLISECS * 1000;
+
+ min = wait == rtsTrue ? 0x7fffffff : 0;
+
+ /*
+ * Collect all of the fd's that we're interested in, and capture
+ * the minimum waiting time (in microseconds) for the delayed threads.
+ */
+ 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;
+ maxfd = (fd > maxfd) ? fd : maxfd;
+ FD_SET(fd, &rfd);
+ continue;
+ }
+
+ case BlockedOnWrite:
+ {
+ int fd = tso->block_info.fd;
+ maxfd = (fd > maxfd) ? fd : maxfd;
+ FD_SET(fd, &wfd);
+ continue;
+ }
+
+ case BlockedOnDelay:
+ {
+ if ((int)tso->block_info.delay < min)
+ min = tso->block_info.delay;
+ continue;
+ }
+
+ default:
+ barf("AwaitEvent");
+ }
+ }
+
+ /* Check for any interesting events */
+
+ tv.tv_sec = min / 1000000;
+ tv.tv_usec = min % 1000000;
+
+ gettimeofday(&tv_before, (struct timezone *) NULL);
+
+ while ((numFound = select(maxfd+1, &rfd, &wfd, NULL, &tv)) < 0) {
+ if (errno != EINTR) {
+ /* fflush(stdout); */
+ fprintf(stderr, "awaitEvent: select failed\n");
+ stg_exit(EXIT_FAILURE);
+ }
+ }
+
+ if (numFound != 0) {
+ /*
+ File descriptors ready, but we don't know how much time was spent
+ in the select(). To interpolate, we compare the time before
+ and after the select().
+ */
+
+ gettimeofday(&tv_after, (struct timezone *) NULL);
+ delta += (tv_after.tv_sec - tv_before.tv_sec) * 1000000 +
+ tv_after.tv_usec - tv_before.tv_usec;
+
+ } else {
+ delta += min;
+ }
+
+ /*
+ Step through the waiting queue, unblocking every thread that now has
+ a file descriptor in a ready state.
+
+ For the delayed threads, decrement the number of microsecs
+ we've been blocked for. Unblock the threads that have thusly expired.
+ */
+
+ prev = NULL;
+ for(tso = blocked_queue_hd; tso != END_TSO_QUEUE; tso = next) {
+ next = tso->link;
+ switch (tso->why_blocked) {
+ case BlockedOnRead:
+ ready = FD_ISSET(tso->block_info.fd, &rfd);
+ break;
+
+ case BlockedOnWrite:
+ ready = FD_ISSET(tso->block_info.fd, &wfd);
+ break;
+
+ case BlockedOnDelay:
+ tso->block_info.delay -= delta;
+ ready = (tso->block_info.delay <= 0);
+ break;
+
+ default:
+ barf("awaitEvent");
+ }
+
+ if (ready) {
+ IF_DEBUG(scheduler,belch("Waking up thread %d\n", tso->id));
+ tso->why_blocked = NotBlocked;
+ tso->link = END_TSO_QUEUE;
+ PUSH_ON_RUN_QUEUE(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;
+ }
+}