X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Frts%2FSelect.c;h=677fdd2c8198103a9e0c095efc532593c405b113;hb=c389ab20bbfd0ea98953d630502a43fe44050f2c;hp=585fe7b4826cd676ab43be2867c64484d18f212c;hpb=bc5c802181b513216bc88f0d1ec9574157ee05fe;p=ghc-hetmet.git diff --git a/ghc/rts/Select.c b/ghc/rts/Select.c index 585fe7b..677fdd2 100644 --- a/ghc/rts/Select.c +++ b/ghc/rts/Select.c @@ -1,12 +1,13 @@ /* ----------------------------------------------------------------------------- - * $Id: Select.c,v 1.17 2001/08/14 13:40:09 sewardj Exp $ + * $Id: Select.c,v 1.29 2003/06/26 12:22:59 stolz Exp $ * - * (c) The GHC Team 1995-1999 + * (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" */ @@ -14,8 +15,10 @@ #include "Schedule.h" #include "RtsUtils.h" #include "RtsFlags.h" +#include "Timer.h" #include "Itimer.h" #include "Signals.h" +#include "Capability.h" # ifdef HAVE_SYS_TYPES_H # include @@ -25,18 +28,22 @@ # include # endif -# ifdef mingw32_TARGET_OS -# include -# endif +#include +#include + +#ifdef HAVE_UNISTD_H +#include +#endif /* last timestamp */ nat timestamp = 0; -/* keep track of the number of ticks since we last called - * gettimeofday(), to avoid having to call it every time we need - * a timestamp. - */ -nat ticks_since_timestamp = 0; +#ifdef RTS_SUPPORTS_THREADS +static rtsBool isWorkerBlockedInAwaitEvent = rtsFalse; +static rtsBool workerWakeupPending = rtsFalse; +static int workerWakeupPipe[2]; +static rtsBool workerWakeupInited = rtsFalse; +#endif /* 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 @@ -87,17 +94,16 @@ awaitEvent(rtsBool wait) StgTSO *tso, *prev, *next; rtsBool ready; fd_set rfd,wfd; -#ifndef mingw32_TARGET_OS int numFound; int maxfd = -1; -#endif 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, belch("scheduler: checking for threads blocked on I/O"); if (wait) { @@ -114,7 +120,6 @@ awaitEvent(rtsBool wait) do { ticks = timestamp = getourtimeofday(); - ticks_since_timestamp = 0; if (wakeUpSleepingThreads(ticks)) { return; } @@ -128,7 +133,6 @@ awaitEvent(rtsBool wait) min = 0x7ffffff; } -#ifndef mingw32_TARGET_OS /* * Collect all of the fd's that we're interested in */ @@ -160,6 +164,15 @@ awaitEvent(rtsBool wait) } } +#ifdef RTS_SUPPORTS_THREADS + if(!workerWakeupInited) { + pipe(workerWakeupPipe); + workerWakeupInited = rtsTrue; + } + FD_SET(workerWakeupPipe[0], &rfd); + maxfd = workerWakeupPipe[0] > maxfd ? workerWakeupPipe[0] : maxfd; +#endif + /* Release the scheduler lock while we do the poll. * this means that someone might muck with the blocked_queue * while we do this, but it shouldn't matter: @@ -172,6 +185,11 @@ awaitEvent(rtsBool wait) * * I believe none of these cases lead to trouble --SDM. */ + +#ifdef RTS_SUPPORTS_THREADS + isWorkerBlockedInAwaitEvent = rtsTrue; + workerWakeupPending = rtsFalse; +#endif RELEASE_LOCK(&sched_mutex); /* Check for any interesting events */ @@ -181,27 +199,47 @@ awaitEvent(rtsBool wait) while ((numFound = select(maxfd+1, &rfd, &wfd, NULL, &tv)) < 0) { if (errno != EINTR) { - - printf("%d\n", errno); - fflush(stdout); - perror("select"); + /* 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 { + fprintf(stderr,"%d\n", errno); + fflush(stderr); + perror("select"); barf("select failed"); + } } -#else /* on mingwin */ - while (1) { - Sleep(0); /* don't busy wait */ -#endif /* mingw32_TARGET_OS */ ACQUIRE_LOCK(&sched_mutex); +#ifdef RTS_SUPPORTS_THREADS + isWorkerBlockedInAwaitEvent = rtsFalse; +#endif -#ifndef mingw32_TARGET_OS /* 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()) { RELEASE_LOCK(&sched_mutex); /* ToDo: kill */ - start_signal_handlers(); + startSignalHandlers(); ACQUIRE_LOCK(&sched_mutex); return; /* still hold the lock */ } @@ -224,6 +262,18 @@ awaitEvent(rtsBool wait) return; /* still hold the lock */ } +#ifdef RTS_SUPPORTS_THREADS + /* If another worker thread wants to take over, + * return to the scheduler + */ + if (needToYieldToReturningWorker()) { + return; /* still hold the lock */ + } +#endif + +#ifdef RTS_SUPPORTS_THREADS + isWorkerBlockedInAwaitEvent = rtsTrue; +#endif RELEASE_LOCK(&sched_mutex); } @@ -234,15 +284,15 @@ awaitEvent(rtsBool wait) */ prev = NULL; - if (select_succeeded) { + 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 = FD_ISSET(tso->block_info.fd, &rfd); + ready = unblock_all || FD_ISSET(tso->block_info.fd, &rfd); break; case BlockedOnWrite: - ready = FD_ISSET(tso->block_info.fd, &wfd); + ready = unblock_all || FD_ISSET(tso->block_info.fd, &wfd); break; default: barf("awaitEvent"); @@ -269,6 +319,36 @@ awaitEvent(rtsBool wait) blocked_queue_tl = prev; } } - + +#if defined(RTS_SUPPORTS_THREADS) + // if we were woken up by wakeBlockedWorkerThread, + // read the dummy byte from the pipe + if(select_succeeded && FD_ISSET(workerWakeupPipe[0], &rfd)) { + unsigned char dummy; + wait = rtsFalse; + read(workerWakeupPipe[0],&dummy,1); + } +#endif } while (wait && !interrupted && run_queue_hd == END_TSO_QUEUE); } + + +#ifdef RTS_SUPPORTS_THREADS +/* wakeBlockedWorkerThread + * + * If a worker thread is currently blocked within awaitEvent, + * wake it. + * Must be called with sched_mutex held. + */ +void +wakeBlockedWorkerThread() +{ + if(isWorkerBlockedInAwaitEvent && !workerWakeupPending) { + unsigned char dummy = 42; // Any value will do here + + // write something so that select() wakes up + write(workerWakeupPipe[1],&dummy,1); + workerWakeupPending = rtsTrue; + } +} +#endif