mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 11:37:35 +00:00
3f0bcdc3ef
- Exhaustively document cancellation points - Rename SIGCANCEL to SIGTHR just like BSDs - Further improve POSIX thread cancellations - Ensure asynchronous cancellations work correctly - Elevate the quality of getrandom() and getentropy() - Make futexes cancel correctly on OpenBSD 6.x and 7.x - Add reboot.com and shutdown.com to examples directory - Remove underscore prefix from awesome timespec_*() APIs - Create assertions that help verify our cancellation points - Remove bad timespec APIs (cmp generalizes eq/ne/gt/gte/lt/lte)
90 lines
4.6 KiB
C
90 lines
4.6 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/cp.internal.h"
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#include "libc/dce.h"
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#include "libc/intrin/asan.internal.h"
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#include "libc/intrin/strace.internal.h"
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#include "libc/sock/struct/pollfd.h"
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#include "libc/sock/struct/pollfd.internal.h"
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#include "libc/sysv/errfuns.h"
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/**
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* Waits for something to happen on multiple file descriptors at once.
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*
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* Warning: XNU has an inconsistency with other platforms. If you have
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* pollfds with fd≥0 and none of the meaningful events flags are added
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* e.g. POLLIN then XNU won't check for POLLNVAL. This matters because
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* one of the use-cases for poll() is quickly checking for open files.
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*
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* Note: Polling works best on Windows for sockets. We're able to poll
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* input on named pipes. But for anything that isn't a socket, or pipe
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* with POLLIN, (e.g. regular file) then POLLIN/POLLOUT are always set
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* into revents if they're requested, provided they were opened with a
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* mode that permits reading and/or writing.
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*
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* Note: Windows has a limit of 64 file descriptors and ENOMEM with -1
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* is returned if that limit is exceeded. In practice the limit is not
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* this low. For example, pollfds with fd<0 don't count. So the caller
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* could flip the sign bit with a short timeout, to poll a larger set.
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*
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* @param fds[𝑖].fd should be a socket, input pipe, or conosle input
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* and if it's a negative number then the entry is ignored
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* @param fds[𝑖].events flags can have POLLIN, POLLOUT, POLLPRI,
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* POLLRDNORM, POLLWRNORM, POLLRDBAND, POLLWRBAND as well as
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* POLLERR, POLLHUP, and POLLNVAL although the latter are
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* always implied (assuming fd≥0) so they're ignored here
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* @param timeout_ms if 0 means don't wait and -1 means wait forever
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* @return number of items fds whose revents field has been set to
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* nonzero to describe its events, or 0 if the timeout elapsed,
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* or -1 w/ errno
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* @return fds[𝑖].revents is always zero initializaed and then will
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* be populated with POLL{IN,OUT,PRI,HUP,ERR,NVAL} if something
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* was determined about the file descriptor
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* @raise ECANCELED if thread was cancelled in masked mode
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* @raise EINTR if signal was delivered
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* @cancellationpoint
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* @asyncsignalsafe
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* @threadsafe
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* @norestart
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*/
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int poll(struct pollfd *fds, size_t nfds, int timeout_ms) {
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int rc;
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size_t n;
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uint64_t millis;
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BEGIN_CANCELLATION_POINT;
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if (IsAsan() && (__builtin_mul_overflow(nfds, sizeof(struct pollfd), &n) ||
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!__asan_is_valid(fds, n))) {
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rc = efault();
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} else if (!IsWindows()) {
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if (!IsMetal()) {
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rc = sys_poll(fds, nfds, timeout_ms);
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} else {
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rc = sys_poll_metal(fds, nfds, timeout_ms);
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}
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} else {
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millis = timeout_ms;
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rc = sys_poll_nt(fds, nfds, &millis, 0);
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}
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END_CANCELLATION_POINT;
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STRACE("poll(%s, %'zu, %'d) → %d% lm", DescribePollFds(rc, fds, nfds), nfds,
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timeout_ms, rc);
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return rc;
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}
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