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* Release 3.77.92.
* Complete implementation of new jobserver algorithm. * A few minor fixups.
This commit is contained in:
Paul Smith
parent
09f1e4cf83
commit
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39
ChangeLog
39
ChangeLog
@ -1,6 +1,43 @@
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1999-08-01 Paul D. Smith <psmith@gnu.org>
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New jobserver algorithm to avoid a possible hole where we could
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miss SIGCHLDs and get into a deadlock. The original algorithm was
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suggested by Roland McGrath with a nice refinement by Paul Eggert.
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Many thanks as well to Tim Magill and Howard Chu, who also
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provided many viable ideas and critiques. We all had a fun week
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dreaming up interesting ways to use and abuse UNIX syscalls :).
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Previously we could miss a SIGCHLD if it happened after we reaped
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the children but before we re-entered the blocking read. If this
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happened to all makes and/or all children, make would never wake
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up.
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We avoid this by having the SIGCHLD handler reset the blocking bit
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on the jobserver pipe read FD (normally read does block in this
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algorithm). Now if the handler is called between the time we reap
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and the time we read(), and there are no tokens available, the
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read will merely return with EAGAIN instead of blocking.
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* main.c (main): Set the blocking bit explicitly here.
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* job.c (child_handler): If we have a jobserver pipe, set the
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non-blocking bit for it.
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(start_waiting_job): Move the token stuff back to new_job; if we
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do it here then we're not controlling the number of remote jobs
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started!
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(new_job): Move the check for job slots to _after_ we've created a
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child structure. If the read returns without getting a token, set
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the blocking bit then try to reap_children.
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* make.h (EINTR_SET): Define to test errno if EINTR is available,
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or 0 otherwise. Just some code cleanup.
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* arscan.c (ar_member_touch): Use it.
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* function.c (func_shell): Use it.
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* job.c (reap_children): Use it.
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* remake.c (touch_file): Use it.
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1999-07-28 Paul D. Smith <psmith@gnu.org>
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* make.h: Define _() and N_() macros as a passthrough to initiate
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* make.h: Define _() and N_() macros as passthrough to initiate
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NLS support.
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* <all>: Add _()/N_() around translatable strings.
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7
arscan.c
7
arscan.c
@ -775,11 +775,8 @@ ar_member_touch (arname, memname)
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if (AR_HDR_SIZE != write (fd, (char *) &ar_hdr, AR_HDR_SIZE))
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goto lose;
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/* The file's mtime is the time we we want. */
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#ifdef EINTR
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while (fstat (fd, &statbuf) < 0 && errno == EINTR);
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#else
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fstat (fd, &statbuf);
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#endif
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while (fstat (fd, &statbuf) < 0 && EINTR_SET)
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;
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#if defined(ARFMAG) || defined(ARFZMAG) || defined(AIAMAG) || defined(WINDOWS32)
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/* Advance member's time to that time */
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for (i = 0; i < sizeof ar_hdr.ar_date; i++)
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@ -3,7 +3,7 @@ AC_REVISION([$Id$])
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AC_PREREQ(2.13)dnl dnl Minimum Autoconf version required.
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AC_INIT(vpath.c)dnl dnl A distinctive file to look for in srcdir.
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AM_INIT_AUTOMAKE(make, 3.77.91)
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AM_INIT_AUTOMAKE(make, 3.77.92)
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AM_CONFIG_HEADER(config.h)
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dnl Regular configure stuff
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@ -1381,11 +1381,7 @@ func_shell (o, argv, funcname)
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if (cc > 0)
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i += cc;
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}
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#ifdef EINTR
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while (cc > 0 || errno == EINTR);
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#else
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while (cc > 0);
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#endif
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while (cc > 0 || EINTR_SET);
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/* Close the read side of the pipe. */
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#ifdef __MSDOS__
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109
job.c
109
job.c
@ -145,6 +145,17 @@ extern int wait ();
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#endif /* Don't have `union wait'. */
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/* How to set close-on-exec for a file descriptor. */
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#if !defined F_SETFD
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# define CLOSE_ON_EXEC(_d)
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#else
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# ifndef FD_CLOEXEC
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# define FD_CLOEXEC 1
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# endif
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# define CLOSE_ON_EXEC(_d) (void) fcntl ((_d), F_SETFD, FD_CLOEXEC)
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#endif
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#ifdef VMS
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static int vms_jobsefnmask = 0;
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#endif /* !VMS */
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@ -218,9 +229,6 @@ int w32_kill(int pid, int sig)
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#endif /* WINDOWS32 */
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#ifndef MAKE_JOBSERVER
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# define free_job_token(c)
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#else
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static void
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free_job_token (child)
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struct child *child;
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@ -248,7 +256,6 @@ free_job_token (child)
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child->job_token = '-';
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}
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#endif
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/* Write an error message describing the exit status given in
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@ -302,14 +309,13 @@ vmsWaitForChildren(int *status)
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/* Handle a dead child. This handler may or may not ever be installed.
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If we're using the jobserver blocking read, we need it. First, installing
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it ensures the read will interrupt on SIGCHLD. Second, we close the dup'd
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read side of the pipe to ensure we don't enter another blocking read
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without reaping all the dead children. In this case we don't need the
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dead_children count.
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it ensures the read will interrupt on SIGCHLD. Second, we reset the
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blocking bit on the read side of the pipe to ensure we don't enter another
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blocking read without reaping all the dead children. In this case we
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don't need the dead_children count.
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If we don't have either waitpid or wait3, then make is unreliable, but we
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use the dead_children count to reap children as best we can. In this case
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job_rfd will never be >= 0. */
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use the dead_children count to reap children as best we can. */
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static unsigned int dead_children = 0;
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@ -319,9 +325,15 @@ child_handler (sig)
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{
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++dead_children;
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if (job_rfd >= 0)
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close (job_rfd);
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job_rfd = -1;
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#ifdef HAVE_JOBSERVER
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if (job_fds[0] >= 0)
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{
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int fl = fcntl(job_fds[0], F_GETFL, 0);
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if (fl >= 0)
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fcntl(job_fds[0], F_SETFL, fl | O_NONBLOCK);
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}
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#endif
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if (debug_flag)
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printf (_("Got a SIGCHLD; %u unreaped children.\n"), dead_children);
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@ -330,11 +342,12 @@ child_handler (sig)
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extern int shell_function_pid, shell_function_completed;
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/* Reap dead children, storing the returned status and the new command
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/* Reap all dead children, storing the returned status and the new command
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state (`cs_finished') in the `file' member of the `struct child' for the
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dead child, and removing the child from the chain. If BLOCK nonzero,
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reap at least one child, waiting for it to die if necessary. If ERR is
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nonzero, print an error message first. */
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dead child, and removing the child from the chain. In addition, if BLOCK
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nonzero, we block in this function until we've reaped at least one
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complete child, waiting for it to die if necessary. If ERR is nonzero,
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print an error message first. */
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void
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reap_children (block, err)
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@ -415,19 +428,18 @@ reap_children (block, err)
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{
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/* A remote status command failed miserably. Punt. */
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remote_status_lose:
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#ifdef EINTR
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if (errno == EINTR)
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if (EINTR_SET)
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continue;
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#endif
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pfatal_with_name ("remote_status");
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}
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else
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{
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/* No remote children. Check for local children. */
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#if !defined(__MSDOS__) && !defined(_AMIGA) && !defined(WINDOWS32)
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if (any_local)
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{
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local_wait:
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#ifdef VMS
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vmsWaitForChildren (&status);
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pid = c->pid;
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@ -446,15 +458,14 @@ reap_children (block, err)
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if (pid < 0)
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{
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/* The wait*() failed miserably. Punt. */
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#ifdef EINTR
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if (errno == EINTR)
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continue;
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#endif
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if (EINTR_SET)
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goto local_wait;
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pfatal_with_name ("wait");
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}
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else if (pid > 0)
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{
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/* We got one; chop the status word up. */
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/* We got a child exit; chop the status word up. */
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exit_code = WEXITSTATUS (status);
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exit_sig = WIFSIGNALED (status) ? WTERMSIG (status) : 0;
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coredump = WCOREDUMP (status);
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@ -1171,20 +1182,16 @@ start_waiting_job (c)
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c->remote = start_remote_job_p (1);
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/* If not, start it locally. */
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if (!c->remote)
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/* If we are running at least one job already and the load average
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is too high, make this one wait. */
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if (!c->remote && job_slots_used > 0 && load_too_high ())
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{
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/* If we are running at least one job already and the load average
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is too high, make this one wait. */
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if (job_slots_used > 0 && load_too_high ())
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{
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/* Put this child on the chain of children waiting
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for the load average to go down. */
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set_command_state (f, cs_running);
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c->next = waiting_jobs;
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waiting_jobs = c;
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return 0;
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}
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/* Put this child on the chain of children waiting for the load average
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to go down. */
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set_command_state (f, cs_running);
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c->next = waiting_jobs;
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waiting_jobs = c;
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return 0;
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}
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/* Start the first command; reap_children will run later command lines. */
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@ -1379,19 +1386,25 @@ new_job (file)
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}
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/* Read a token. As long as there's no token available we'll block.
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If we get a SIGCHLD we'll return with EINTR. If one happened
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before we got here we'll return with EBADF. */
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else if (read (job_rfd, &c->job_token, 1) < 1)
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before we got here we'll return immediately with EAGAIN because
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the signal handler unsets the blocking bit. */
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else if (read (job_fds[0], &c->job_token, 1) < 1)
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{
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if (errno == EINTR)
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;
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int fl;
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/* If EBADF, we got a SIGCHLD before. Otherwise, who knows? */
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else if (errno != EBADF)
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#if !defined(EAGAIN)
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# define EAGAIN EWOULDBLOCK
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#endif
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if (errno != EINTR && errno != EAGAIN)
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pfatal_with_name (_("read jobs pipe"));
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/* Something's done; reap it. We don't force a block here; if
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something strange happened and nothing's ready, just come back
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and wait some more. */
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/* Set the blocking bit on the read FD again, just in case. */
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fl = fcntl(job_fds[0], F_GETFL, 0);
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if (fl >= 0)
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fcntl(job_fds[0], F_SETFL, fl & ~O_NONBLOCK);
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/* Something's done. We don't want to block for a whole child,
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just reap whatever's there. */
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reap_children (0, 0);
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}
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11
main.c
11
main.c
@ -205,7 +205,6 @@ static unsigned int inf_jobs = 0;
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/* File descriptors for the jobs pipe. */
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int job_fds[2] = { -1, -1 };
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int job_rfd = -1;
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/* Maximum load average at which multiple jobs will be run.
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Negative values mean unlimited, while zero means limit to
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@ -1353,15 +1352,13 @@ int main (int argc, char ** argv)
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job_slots_str = xstrdup(buf);
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}
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/* If we have a jobserver pipe, dup(2) the read end. We'll use that in
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the child handler to note a child has died. See job.c. */
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/* Be sure the blocking bit on the read FD is set to start with. */
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if (job_fds[0] >= 0)
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{
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job_rfds = dup (job_fds[0]);
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CLOSE_ON_EXEC (job_rfds);
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int fl = fcntl(job_fds[0], F_GETFL, 0);
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if (fl >= 0)
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fcntl(job_fds[0], F_SETFL, fl & ~O_NONBLOCK);
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}
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#endif
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/* Set up MAKEFLAGS and MFLAGS again, so they will be right. */
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8
make.h
8
make.h
@ -77,6 +77,14 @@ Boston, MA 02111-1307, USA. */
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extern int errno;
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#endif
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/* A shortcut for EINTR checking. Note you should never negate this! That
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very likely doesn't mean what you want if EINTR is not available. */
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#ifdef EINTR
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# define EINTR_SET (errno == EINTR)
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#else
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# define EINTR_SET (0)
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#endif
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#ifndef isblank
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# define isblank(c) ((c) == ' ' || (c) == '\t')
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#endif
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7
remake.c
7
remake.c
@ -918,13 +918,10 @@ touch_file (file)
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char buf;
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int status;
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#ifdef EINTR
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do
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#endif
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status = fstat (fd, &statbuf);
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#ifdef EINTR
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while (status < 0 && errno == EINTR);
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#endif
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while (status < 0 && EINTR_SET);
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if (status < 0)
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TOUCH_ERROR ("touch: fstat: ");
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/* Rewrite character 0 same as it already is. */
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