171 lines
4.3 KiB
Diff
171 lines
4.3 KiB
Diff
From b552b05251980f693c729e251f93f5225b400714 Mon Sep 17 00:00:00 2001
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From: Paul Smith <psmith@gnu.org>
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Date: Sat, 3 Jun 2017 16:20:51 -0400
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Subject: [SV 51159] Use a non-blocking read with pselect to avoid hangs.
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* posixos.c (set_blocking): Set blocking on a file descriptor.
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(jobserver_setup): Set non-blocking on the jobserver read side.
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(jobserver_parse_auth): Ditto.
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(jobserver_acquire_all): Set blocking to avoid a busy-wait loop.
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(jobserver_acquire): If the non-blocking read() returns without
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taking a token then try again.
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---
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posixos.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++-----------------
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1 file changed, 71 insertions(+), 26 deletions(-)
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diff --git posixos.c posixos.c
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index e642d7f..dbafa51 100644
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--- posixos.c
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+++ posixos.c
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@@ -62,6 +62,24 @@ make_job_rfd (void)
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#endif
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}
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+static void
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+set_blocking (int fd, int blocking)
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+{
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+ // If we're not using pselect() don't change the blocking
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+#ifdef HAVE_PSELECT
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+ int flags;
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+ EINTRLOOP (flags, fcntl (fd, F_GETFL));
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+ if (flags >= 0)
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+ {
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+ int r;
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+ flags = blocking ? (flags & ~O_NONBLOCK) : (flags | O_NONBLOCK);
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+ EINTRLOOP (r, fcntl (fd, F_SETFL, flags));
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+ if (r < 0)
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+ pfatal_with_name ("fcntl(O_NONBLOCK)");
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+ }
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+#endif
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+}
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+
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unsigned int
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jobserver_setup (int slots)
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{
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@@ -86,6 +104,9 @@ jobserver_setup (int slots)
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pfatal_with_name (_("init jobserver pipe"));
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}
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+ /* When using pselect() we want the read to be non-blocking. */
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+ set_blocking (job_fds[0], 0);
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+
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return 1;
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}
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@@ -121,6 +142,9 @@ jobserver_parse_auth (const char *auth)
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return 0;
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}
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+ /* When using pselect() we want the read to be non-blocking. */
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+ set_blocking (job_fds[0], 0);
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+
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return 1;
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}
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@@ -169,7 +193,10 @@ jobserver_acquire_all (void)
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{
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unsigned int tokens = 0;
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- /* Close the write side, so the read() won't hang. */
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+ /* Use blocking reads to wait for all outstanding jobs. */
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+ set_blocking (job_fds[0], 1);
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+
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+ /* Close the write side, so the read() won't hang forever. */
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close (job_fds[1]);
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job_fds[1] = -1;
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@@ -236,18 +263,12 @@ jobserver_pre_acquire (void)
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unsigned int
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jobserver_acquire (int timeout)
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{
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- sigset_t empty;
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- fd_set readfds;
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struct timespec spec;
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struct timespec *specp = NULL;
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- int r;
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- char intake;
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+ sigset_t empty;
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sigemptyset (&empty);
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- FD_ZERO (&readfds);
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- FD_SET (job_fds[0], &readfds);
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-
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if (timeout)
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{
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/* Alarm after one second (is this too granular?) */
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@@ -256,28 +277,52 @@ jobserver_acquire (int timeout)
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specp = &spec;
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}
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- r = pselect (job_fds[0]+1, &readfds, NULL, NULL, specp, &empty);
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-
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- if (r == -1)
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+ while (1)
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{
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- /* Better be SIGCHLD. */
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- if (errno != EINTR)
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- pfatal_with_name (_("pselect jobs pipe"));
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- return 0;
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- }
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+ fd_set readfds;
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+ int r;
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+ char intake;
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- if (r == 0)
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- /* Timeout. */
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- return 0;
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+ FD_ZERO (&readfds);
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+ FD_SET (job_fds[0], &readfds);
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- /* The read FD is ready: read it! */
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- EINTRLOOP (r, read (job_fds[0], &intake, 1));
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- if (r < 0)
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- pfatal_with_name (_("read jobs pipe"));
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+ r = pselect (job_fds[0]+1, &readfds, NULL, NULL, specp, &empty);
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+ if (r < 0)
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+ switch (errno)
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+ {
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+ case EINTR:
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+ /* SIGCHLD will show up as an EINTR. */
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+ return 0;
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+
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+ case EBADF:
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+ /* Someone closed the jobs pipe.
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+ That shouldn't happen but if it does we're done. */
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+ O (fatal, NILF, _("job server shut down"));
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- /* What does it mean if read() returns 0? It shouldn't happen because only
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- the master make can reap all the tokens and close the write side...?? */
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- return r > 0;
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+ default:
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+ pfatal_with_name (_("pselect jobs pipe"));
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+ }
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+
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+ if (r == 0)
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+ /* Timeout. */
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+ return 0;
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+
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+ /* The read FD is ready: read it! This is non-blocking. */
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+ EINTRLOOP (r, read (job_fds[0], &intake, 1));
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+
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+ if (r < 0)
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+ {
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+ /* Someone sniped our token! Try again. */
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+ if (errno == EAGAIN)
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+ continue;
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+
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+ pfatal_with_name (_("read jobs pipe"));
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+ }
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+
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+ /* read() should never return 0: only the master make can reap all the
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+ tokens and close the write side...?? */
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+ return r > 0;
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+ }
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}
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#else
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--
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cgit v1.0-41-gc330
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