diff options
| -rw-r--r-- | NEWS | 4 | ||||
| -rw-r--r-- | src/iopoll.c | 135 | ||||
| -rw-r--r-- | src/iopoll.h | 3 | ||||
| -rw-r--r-- | src/tee.c | 5 | ||||
| -rwxr-xr-x | tests/misc/tee.sh | 17 |
5 files changed, 139 insertions, 25 deletions
@@ -172,6 +172,10 @@ GNU coreutils NEWS -*- outline -*- tee -p detects when all remaining outputs have become broken pipes, and exits, rather than waiting for more input to induce an exit when written. + tee now handles non blocking outputs, which can be seen for example with + telnet or mpirun piping through tee to a terminal. + Previously tee could truncate data written to such an output and fail, + and also potentially output a "Resource temporarily unavailable" error. * Noteworthy changes in release 9.1 (2022-04-15) [stable] diff --git a/src/iopoll.c b/src/iopoll.c index ca27595e3..b211dafc8 100644 --- a/src/iopoll.c +++ b/src/iopoll.c @@ -1,5 +1,5 @@ -/* iopoll.c -- broken pipe detection (while waiting for input) - Copyright (C) 1989-2022 Free Software Foundation, Inc. +/* iopoll.c -- broken pipe detection / non blocking output handling + Copyright (C) 2022 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -20,10 +20,10 @@ #include <assert.h> - /* poll(2) is needed on AIX (where 'select' gives a readable - event immediately) and Solaris (where 'select' never gave - a readable event). Also use poll(2) on systems we know work - and/or are already using poll (linux). */ +/* poll(2) is needed on AIX (where 'select' gives a readable + event immediately) and Solaris (where 'select' never gave + a readable event). Also use poll(2) on systems we know work + and/or are already using poll (linux). */ #if defined _AIX || defined __sun || defined __APPLE__ || \ defined __linux__ || defined __ANDROID__ @@ -47,25 +47,36 @@ #include "isapipe.h" -/* Wait for FDIN to become ready for reading or FDOUT to become a broken pipe. +/* BROKEN_OUTPUT selects the mode of operation of this function. + If BROKEN_OUTPUT, wait for FDIN to become ready for reading + or FDOUT to become a broken pipe. + If !BROKEN_OUTPUT, wait for FDIN or FDOUT to become ready for writing. If either of those are -1, then they're not checked. Set BLOCK to true to wait for an event, otherwise return the status immediately. Return 0 if not BLOCKing and there is no event on the requested descriptors. Return 0 if FDIN can be read() without blocking, or IOPOLL_BROKEN_OUTPUT if - FDOUT becomes a broken pipe, otherwise IOPOLL_ERROR if there is a poll() - or select() error. */ + FDOUT becomes a broken pipe. If !BROKEN_OUTPUT return 0 if FDOUT writeable. + Otherwise return IOPOLL_ERROR if there is a poll() or select() error. */ -extern int -iopoll (int fdin, int fdout, bool block) +static int +iopoll_internal (int fdin, int fdout, bool block, bool broken_output) { -#if IOPOLL_USES_POLL + assert (fdin != -1 || fdout != -1); +#if IOPOLL_USES_POLL struct pollfd pfds[2] = { /* POLLRDBAND needed for illumos, macOS. */ { .fd = fdin, .events = POLLIN | POLLRDBAND, .revents = 0 }, { .fd = fdout, .events = POLLRDBAND, .revents = 0 }, }; + int check_out_events = POLLERR | POLLHUP | POLLNVAL; int ret = 0; + if (! broken_output) + { + pfds[0].events = pfds[1].events = POLLOUT; + check_out_events = POLLOUT; + } + while (0 <= ret || errno == EINTR) { ret = poll (pfds, 2, block ? -1 : 0); @@ -77,8 +88,8 @@ iopoll (int fdin, int fdout, bool block) assert (0 < ret); if (pfds[0].revents) /* input available or pipe closed indicating EOF; */ return 0; /* should now be able to read() without blocking */ - if (pfds[1].revents) /* POLLERR, POLLHUP (or POLLNVAL) */ - return IOPOLL_BROKEN_OUTPUT; /* output error or broken pipe */ + if (pfds[1].revents & check_out_events) + return broken_output ? IOPOLL_BROKEN_OUTPUT : 0; } #else /* fall back to select()-based implementation */ @@ -96,31 +107,40 @@ iopoll (int fdin, int fdout, bool block) as ready for reading. Assumes fdout is not actually readable. */ while (0 <= ret || errno == EINTR) { - fd_set rfds; - FD_ZERO (&rfds); + fd_set fds; + FD_ZERO (&fds); if (0 <= fdin) - FD_SET (fdin, &rfds); + FD_SET (fdin, &fds); if (0 <= fdout) - FD_SET (fdout, &rfds); + FD_SET (fdout, &fds); struct timeval delay = { .tv_sec = 0, .tv_usec = 0 }; - ret = select (nfds, &rfds, NULL, NULL, block ? NULL : &delay); + ret = select (nfds, + broken_output ? &fds : NULL, + broken_output ? NULL : &fds, + NULL, block ? NULL : &delay); if (ret < 0) continue; if (ret == 0 && ! block) return 0; assert (0 < ret); - if (0 <= fdin && FD_ISSET (fdin, &rfds)) /* input available or EOF; */ + if (0 <= fdin && FD_ISSET (fdin, &fds)) /* input available or EOF; */ return 0; /* should now be able to read() without blocking */ - if (0 <= fdout && FD_ISSET (fdout, &rfds)) /* equiv to POLLERR */ - return IOPOLL_BROKEN_OUTPUT; /* output error or broken pipe */ + if (0 <= fdout && FD_ISSET (fdout, &fds)) /* equiv to POLLERR */ + return broken_output ? IOPOLL_BROKEN_OUTPUT : 0; } #endif return IOPOLL_ERROR; } +extern int +iopoll (int fdin, int fdout, bool block) +{ + return iopoll_internal (fdin, fdout, block, true); +} + /* Return true if fdin is relevant for iopoll(). @@ -145,3 +165,74 @@ iopoll_output_ok (int fdout) { return isapipe (fdout) > 0; } + +#ifdef EWOULDBLOCK +# define IS_EAGAIN(errcode) ((errcode) == EAGAIN || (errcode) == EWOULDBLOCK) +#else +# define IS_EAGAIN(errcode) ((errcode) == EAGAIN) +#endif + +/* Inspect the errno of the previous syscall. + On EAGAIN, wait for the underlying file descriptor to become writable. + Return true, if EAGAIN has been successfully handled. */ + +static bool +fwait_for_nonblocking_write (FILE *f) +{ + if (! IS_EAGAIN (errno)) + /* non-recoverable write error */ + return false; + + int fd = fileno (f); + if (fd == -1) + goto fail; + + /* wait for the file descriptor to become writable */ + if (iopoll_internal (-1, fd, true, false) != 0) + goto fail; + + /* successfully waited for the descriptor to become writable */ + clearerr (f); + return true; + +fail: + errno = EAGAIN; + return false; +} + + +/* wrapper for fclose() that also waits for F if non blocking. */ + +extern bool +fclose_nonblock (FILE *f) +{ + for (;;) + { + if (fclose (f) == 0) + return true; + + if (! fwait_for_nonblocking_write (f)) + return false; + } +} + + +/* wrapper for fwrite() that also waits for F if non blocking. */ + +extern bool +fwrite_nonblock (char const *buf, ssize_t size, FILE *f) +{ + for (;;) + { + const size_t written = fwrite (buf, 1, size, f); + size -= written; + assert (size >= 0); + if (size <= 0) /* everything written */ + return true; + + if (! fwait_for_nonblocking_write (f)) + return false; + + buf += written; + } +} diff --git a/src/iopoll.h b/src/iopoll.h index 00fc99836..79d5ccfef 100644 --- a/src/iopoll.h +++ b/src/iopoll.h @@ -4,3 +4,6 @@ int iopoll (int fdin, int fdout, bool block); bool iopoll_input_ok (int fdin); bool iopoll_output_ok (int fdout); + +bool fclose_nonblock (FILE *f); +bool fwrite_nonblock (char const *buf, ssize_t size, FILE *f); @@ -26,6 +26,7 @@ #include "die.h" #include "error.h" #include "fadvise.h" +#include "iopoll.h" #include "stdio--.h" #include "xbinary-io.h" #include "iopoll.h" @@ -313,7 +314,7 @@ tee_files (int nfiles, char **files, bool pipe_check) Standard output is the first one. */ for (i = 0; i <= nfiles; i++) if (descriptors[i] - && fwrite (buffer, bytes_read, 1, descriptors[i]) != 1) + && ! fwrite_nonblock (buffer, bytes_read, descriptors[i])) { if (fail_output (descriptors, files, i)) ok = false; @@ -331,7 +332,7 @@ tee_files (int nfiles, char **files, bool pipe_check) /* Close the files, but not standard output. */ for (i = 1; i <= nfiles; i++) - if (descriptors[i] && fclose (descriptors[i]) != 0) + if (descriptors[i] && ! fclose_nonblock (descriptors[i])) { error (0, errno, "%s", quotef (files[i])); ok = false; diff --git a/tests/misc/tee.sh b/tests/misc/tee.sh index 63e7524c0..ce0cfd41d 100755 --- a/tests/misc/tee.sh +++ b/tests/misc/tee.sh @@ -79,8 +79,23 @@ touch file.ro || framework_failure_ chmod a-w file.ro || framework_failure_ returns_ 1 tee -p </dev/null file.ro || fail=1 -# Ensure tee honors --output-error modes mkfifo_or_skip_ fifo + +# Ensure tee handles nonblocking output correctly +# Terminate any background processes +cleanup_() { kill $pid 2>/dev/null && wait $pid; } +read_fifo_delayed() { + { sleep .1; timeout 10 dd of=/dev/null status=none; } <fifo +} +read_fifo_delayed & pid=$! +dd count=20 bs=100K if=/dev/zero status=none | +{ + dd count=0 oflag=nonblock status=none + tee || { cleanup_; touch tee.fail; } +} >fifo +test -f tee.fail && fail=1 + +# Ensure tee honors --output-error modes read_fifo() { timeout 10 dd count=1 if=fifo of=/dev/null status=none & } # Determine platform sigpipe exit status |