From: Matt Birkholz Date: Fri, 24 Jul 2015 00:54:30 +0000 (-0700) Subject: Fix test-select-registry to "atomically" unmask interrupts. X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=c0816ccc3db619866dad4da50f33ab6d8edabc4d;p=mit-scheme.git Fix test-select-registry to "atomically" unmask interrupts. When SMPing the machine cannot miss e.g a global-GC interrupt, else the whole world grinds to a halt. Using (set-interrupt-enables! interrupt-mask/all) and then (test-select-registry ... #t) admits a small "hole" wherein such an interrupt can drop, allowing the machine to block without realizing it missed an interrupt intended to wake it. The test-select-registry primitive does not actually "atomically unmask interrupts" but simply ignores the mask inside its critical section -- as if the mask was interrupt-mask/all. Adjust branches so that, when not blocking, the simpler poll/select is called (rather than ppoll/pselect). Eliminate loops that re-try after masked interrupts arrive since all interrupts are considered unmasked here. Conflicts: src/runtime/thread.scm --- diff --git a/src/microcode/uxio.c b/src/microcode/uxio.c index 649d8daa1..5dcd3d4d5 100644 --- a/src/microcode/uxio.c +++ b/src/microcode/uxio.c @@ -554,19 +554,27 @@ safe_poll (struct pollfd *fds, nfds_t nfds, int blockp) { int n; -#ifdef HAVE_PPOLL if (!blockp) { - n = (UX_poll (fds, nfds, 0)); + if ((OS_process_any_status_change ())) + { + errno = EINTR; + n = -1; + } + else + { + n = (UX_poll (fds, nfds, 0)); + } } else +#ifdef HAVE_PPOLL { sigset_t old, new; UX_sigfillset (&new); UX_sigprocmask (SIG_SETMASK, &new, &old); if ((OS_process_any_status_change ()) - || (pending_interrupts_p ())) + || ((GET_INT_CODE) != 0)) { errno = EINTR; n = -1; @@ -578,12 +586,13 @@ safe_poll (struct pollfd *fds, nfds_t nfds, int blockp) UX_sigprocmask (SIG_SETMASK, &old, NULL); } #else /* not HAVE_PPOLL */ - /* There is a signal "hole" here, but what can we do without ppoll()? */ - INTERRUPTABLE_EXTENT - (n, (((OS_process_any_status_change ()) - || (pending_interrupts_p ())) - ? ((errno = EINTR), (-1)) - : (UX_poll (fds, nfds, (blockp ? INFTIM : 0))))); + { + INTERRUPTABLE_EXTENT + (n, (((OS_process_any_status_change ()) + || ((GET_INT_CODE) != 0)) + ? ((errno = EINTR), (-1)) + : (UX_poll (fds, nfds, (blockp ? INFTIM : 0))))); + } #endif return (n); @@ -592,41 +601,37 @@ safe_poll (struct pollfd *fds, nfds_t nfds, int blockp) int OS_test_select_registry (select_registry_t registry, int blockp) { + int nfds; struct select_registry_s * r = registry; - while (1) - { - int nfds = (safe_poll ((SR_ENTRIES (r)), (SR_N_FDS (r)), blockp)); - if (nfds >= 0) - return (nfds); - if (errno != EINTR) - error_system_call (errno, syscall_select); - if (OS_process_any_status_change ()) - return (SELECT_PROCESS_STATUS_CHANGE); - if (pending_interrupts_p ()) - return (SELECT_INTERRUPT); - } + + nfds = (safe_poll ((SR_ENTRIES (r)), (SR_N_FDS (r)), blockp)); + if (nfds >= 0) + return (nfds); + if (errno != EINTR) + error_system_call (errno, syscall_select); + if (OS_process_any_status_change ()) + return (SELECT_PROCESS_STATUS_CHANGE); + return (SELECT_INTERRUPT); } int OS_test_select_descriptor (int fd, int blockp, unsigned int mode) { + int nfds; struct pollfd pfds [1]; ((pfds [0]) . fd) = fd; ((pfds [0]) . events) = (DECODE_MODE (mode)); - while (1) - { - int nfds = (safe_poll (pfds, 1, blockp)); - if (nfds > 0) - return (ENCODE_MODE ((pfds [0]) . revents)); - if (nfds == 0) - return (0); - if (errno != EINTR) - error_system_call (errno, syscall_select); - if (OS_process_any_status_change ()) - return (SELECT_PROCESS_STATUS_CHANGE); - if (pending_interrupts_p ()) - return (SELECT_INTERRUPT); - } + + nfds = (safe_poll (pfds, 1, blockp)); + if (nfds > 0) + return (ENCODE_MODE ((pfds [0]) . revents)); + if (nfds == 0) + return (0); + if (errno != EINTR) + error_system_call (errno, syscall_select); + if (OS_process_any_status_change ()) + return (SELECT_PROCESS_STATUS_CHANGE); + return (SELECT_INTERRUPT); } #else /* not HAVE_POLL */ @@ -748,19 +753,27 @@ safe_select (int nfds, SELECT_TYPE *readfds, SELECT_TYPE *writefds, int blockp) { int n; -#ifdef HAVE_PSELECT if (!blockp) { - n = (UX_select (nfds, readfds, writefds, NULL, &zero_timeout)); + if ((OS_process_any_status_change ())) + { + errno = EINTR; + n = -1; + } + else + { + n = (UX_select (nfds, readfds, writefds, NULL, &zero_timeout)); + } } else +#ifdef HAVE_PSELECT { sigset_t old, new; UX_sigfillset (&new); UX_sigprocmask (SIG_SETMASK, &new, &old); if ((OS_process_any_status_change ()) - || (pending_interrupts_p ())) + || ((GET_INT_CODE) != 0)) { errno = EINTR; n = -1; @@ -772,13 +785,14 @@ safe_select (int nfds, SELECT_TYPE *readfds, SELECT_TYPE *writefds, int blockp) UX_sigprocmask (SIG_SETMASK, &old, NULL); } #else /* not HAVE_PSELECT */ - /* There is a signal "hole" here, but what can we do without pselect()? */ - INTERRUPTABLE_EXTENT - (n, (((OS_process_any_status_change ()) - || (pending_interrupts_p ())) - ? ((errno = EINTR), (-1)) - : (UX_select (nfds, readfds, writefds, NULL, - (blockp ? NULL : &zero_timeout))))); + { + INTERRUPTABLE_EXTENT + (n, (((OS_process_any_status_change ()) + || ((GET_INT_CODE) != 0)) + ? ((errno = EINTR), (-1)) + : (UX_select (nfds, readfds, writefds, NULL, + (blockp ? NULL : &zero_timeout))))); + } #endif return (n); @@ -788,25 +802,22 @@ int OS_test_select_registry (select_registry_t registry, int blockp) { #ifdef HAVE_SELECT + int nfds; struct select_registry_s * r = registry; (* (SR_RREADERS (r))) = (* (SR_QREADERS (r))); (* (SR_RWRITERS (r))) = (* (SR_QWRITERS (r))); - while (1) - { - int nfds = (safe_select (FD_SETSIZE, - (SR_RREADERS (r)), - (SR_RWRITERS (r)), - blockp)); - if (nfds >= 0) - return (nfds); - if (errno != EINTR) - error_system_call (errno, syscall_select); - if (OS_process_any_status_change ()) - return (SELECT_PROCESS_STATUS_CHANGE); - if (pending_interrupts_p ()) - return (SELECT_INTERRUPT); - } + nfds = (safe_select (FD_SETSIZE, + (SR_RREADERS (r)), + (SR_RWRITERS (r)), + blockp)); + if (nfds >= 0) + return (nfds); + if (errno != EINTR) + error_system_call (errno, syscall_select); + if (OS_process_any_status_change ()) + return (SELECT_PROCESS_STATUS_CHANGE); + return (SELECT_INTERRUPT); #else error_system_call (ENOSYS, syscall_select); return (1); @@ -817,6 +828,7 @@ int OS_test_select_descriptor (int fd, int blockp, unsigned int mode) { #ifdef HAVE_SELECT + int nfds; SELECT_TYPE readable; SELECT_TYPE writeable; @@ -828,22 +840,18 @@ OS_test_select_descriptor (int fd, int blockp, unsigned int mode) if ((mode & SELECT_MODE_WRITE) != 0) FD_SET (fd, (&writeable)); - while (1) - { - int nfds = (safe_select (fd + 1, &readable, &writeable, blockp)); - if (nfds > 0) - return - (((FD_ISSET (fd, (&readable))) ? SELECT_MODE_READ : 0) - | ((FD_ISSET (fd, (&writeable))) ? SELECT_MODE_WRITE : 0)); - if (nfds == 0) - return (0); - if (errno != EINTR) - error_system_call (errno, syscall_select); - if (OS_process_any_status_change ()) - return (SELECT_PROCESS_STATUS_CHANGE); - if (pending_interrupts_p ()) - return (SELECT_INTERRUPT); - } + nfds = (safe_select (fd + 1, &readable, &writeable, blockp)); + if (nfds > 0) + return + (((FD_ISSET (fd, (&readable))) ? SELECT_MODE_READ : 0) + | ((FD_ISSET (fd, (&writeable))) ? SELECT_MODE_WRITE : 0)); + if (nfds == 0) + return (0); + if (errno != EINTR) + error_system_call (errno, syscall_select); + if (OS_process_any_status_change ()) + return (SELECT_PROCESS_STATUS_CHANGE); + return (SELECT_INTERRUPT); #else error_system_call (ENOSYS, syscall_select); return (1); @@ -863,7 +871,7 @@ OS_pause (void) UX_sigprocmask (SIG_SETMASK, &new, &old); if (OS_process_any_status_change ()) n = SELECT_PROCESS_STATUS_CHANGE; - else if (pending_interrupts_p ()) + else if ((GET_INT_CODE) != 0) n = SELECT_INTERRUPT; else { @@ -877,7 +885,7 @@ OS_pause (void) #else /* not HAVE_SIGSUSPEND */ INTERRUPTABLE_EXTENT (n, (((OS_process_any_status_change ()) - || (pending_interrupts_p ())) + || ((GET_INT_CODE) != 0)) ? ((errno = EINTR), (-1)) : ((UX_pause ()), (0)))); if (OS_process_any_status_change()) diff --git a/src/runtime/thread.scm b/src/runtime/thread.scm index 87ccd2aab..4a2181f68 100644 --- a/src/runtime/thread.scm +++ b/src/runtime/thread.scm @@ -651,9 +651,9 @@ USA. (%assert (not (%thread id)) "wait-for-io: not idle") (%maybe-toggle-thread-timer #f) (let ((result (begin - (unlock) + (%unlock) (test-select-registry io-registry #t)))) - (lock) + (%lock) (signal-select-result result) (run-first-thread id)))