Attachment 232656 Details for Bug 262738 – Add support for locking FDs to lockf

[patch] Add support for locking FDs to lockf

lockf-fds.diff (text/plain), 4.51 KB, created by Daniel O'Connor on 2022-03-23 12:20:57 UTC

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Creator: Daniel O'Connor

Created: 2022-03-23 12:20:57 UTC

Size: 4.51 KB

patch

obsolete

>diff -ur lockf.orig/Makefile lockf/Makefile
>--- lockf.orig/Makefile	2022-03-23 21:44:16.000000000 +1030
>+++ lockf/Makefile	2022-03-23 22:02:30.000000000 +1030
>@@ -1,5 +1,5 @@
> # $FreeBSD: stable/12/usr.bin/lockf/Makefile 90415 2002-02-08 22:31:43Z markm $
> 
> PROG=	lockf
>-
>+CFLAGS+=-g
> .include <bsd.prog.mk>
>Only in lockf: lockf
>diff -ur lockf.orig/lockf.1 lockf/lockf.1
>--- lockf.orig/lockf.1	2022-03-23 21:44:16.000000000 +1030
>+++ lockf/lockf.1	2022-03-23 22:46:46.000000000 +1030
>@@ -29,19 +29,23 @@
> .Os
> .Sh NAME
> .Nm lockf
>-.Nd execute a command while holding a file lock
>+.Nd execute a command while holding a file/fd lock
> .Sh SYNOPSIS
> .Nm
> .Op Fl kns
> .Op Fl t Ar seconds
>-.Ar file
>+.Ar file|fd
> .Ar command
> .Op Ar arguments
>+.Nm
>+.Op Fl kns
>+.Op Fl t Ar seconds
>+.Ar fd
> .Sh DESCRIPTION
> The
> .Nm
> utility acquires an exclusive lock on a
>-.Ar file ,
>+.Ar file|fd ,
> creating it if necessary,
> .Bf Em
> and removing the file on exit unless explicitly told not to.
>@@ -64,7 +68,14 @@
> .Xr flock 2 ;
> the mere existence of the
> .Ar file
>-is not considered to constitute a lock.
>+is not considered to constitute a lock. If
>+.Ar file|fd
>+is an integer greater than 0 then it will be interpreted as
>+file descriptor number. This implicitly sets the
>+.Fl k
>+option. If a file descriptor is used then
>+.Ar command
>+is optional. This can be used to lock inside a shell script.
> .Pp
> If the
> .Nm
>@@ -160,6 +171,31 @@
> did not exit normally,
> but may have been signaled or stopped.
> .El
>+.Sh EXAMPLES
>+Lock a file and run a script, return immediately if the lock is not
>+available. Do not delete the file afterward so lock order is
>+guaranteed.
>+.Pp
>+.Dl $ lockf -t 0 -k /tmp/my.lock myscript
>+.Pp
>+Protect a section of a shell script with a lock, wait up to 5 seconds
>+for it to become available. In this case
>+.Fl k
>+is implied.
>+.Pp
>+.Bd -literal -offset indent
>+(
>+	lockf -s -t 10 9
>+	if [ $? -ne 0 ]; then
>+		echo "Failed to obtain lock"
>+		exit 1
>+	fi
>+
>+	echo Start
>+	# Do some stuff
>+	echo End
>+) 9>/tmp/my.lock
>+.Ed
> .Sh SEE ALSO
> .Xr flock 2 ,
> .Xr lockf 3 ,
>Only in lockf: lockf.1.gz
>diff -ur lockf.orig/lockf.c lockf/lockf.c
>--- lockf.orig/lockf.c	2022-03-23 21:44:16.000000000 +1030
>+++ lockf/lockf.c	2022-03-23 22:16:05.000000000 +1030
>@@ -50,6 +50,7 @@
> static const char *lockname;
> static int lockfd = -1;
> static int keep;
>+static int fdlock;
> static volatile sig_atomic_t timed_out;
> 
> /*
>@@ -88,9 +89,17 @@
> 			usage();
> 		}
> 	}
>-	if (argc - optind < 2)
>-		usage();
>+
> 	lockname = argv[optind++];
>+
>+	if (atoi(lockname) > 2)
>+		fdlock = 1;
>+	else
>+		fdlock = 0;
>+
>+	if (argc - optind < 1 - fdlock)
>+		usage();
>+
> 	argc -= optind;
> 	argv += optind;
> 	if (waitsec > 0) {		/* Set up a timeout. */
>@@ -126,7 +135,7 @@
> 	 */
> 	lockfd = acquire_lock(lockname, flags | O_NONBLOCK);
> 	while (lockfd == -1 && !timed_out && waitsec != 0) {
>-		if (keep)
>+		if (keep || fdlock)
> 			lockfd = acquire_lock(lockname, flags);
> 		else {
> 			wait_for_lock(lockname);
>@@ -140,7 +149,13 @@
> 			exit(EX_TEMPFAIL);
> 		errx(EX_TEMPFAIL, "%s: already locked", lockname);
> 	}
>+
> 	/* At this point, we own the lock. */
>+
>+	/* Nothing else to do for FD lock, just exit */
>+	if (fdlock)
>+		return 0;
>+
> 	if (atexit(cleanup) == -1)
> 		err(EX_OSERR, "atexit failed");
> 	if ((child = fork()) == -1)
>@@ -161,7 +176,7 @@
> }
> 
> /*
>- * Try to acquire a lock on the given file, creating the file if
>+ * Try to acquire a lock on the given file/fd, creating the file if
>  * necessary.  The flags argument is O_NONBLOCK or 0, depending on
>  * whether we should wait for the lock.  Returns an open file descriptor
>  * on success, or -1 on failure.
>@@ -171,12 +186,20 @@
> {
> 	int fd;
> 
>-	if ((fd = open(name, O_RDONLY|O_EXLOCK|flags, 0666)) == -1) {
>-		if (errno == EAGAIN || errno == EINTR)
>-			return (-1);
>-		else if (errno == ENOENT && (flags & O_CREAT) == 0)
>-			err(EX_UNAVAILABLE, "%s", name);
>-		err(EX_CANTCREAT, "cannot open %s", name);
>+	if ((fd = atoi(name)) > 0) {
>+		if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
>+			if (errno == EAGAIN || errno == EINTR)
>+				return (-1);
>+			err(EX_CANTCREAT, "cannot lock FD %d", fd);
>+		}
>+	} else {
>+		if ((fd = open(name, O_RDONLY|O_EXLOCK|flags, 0666)) == -1) {
>+			if (errno == EAGAIN || errno == EINTR)
>+				return (-1);
>+			else if (errno == ENOENT && (flags & O_CREAT) == 0)
>+				err(EX_UNAVAILABLE, "%s", name);
>+			err(EX_CANTCREAT, "cannot open %s", name);
>+		}
> 	}
> 	return (fd);
> }
>@@ -188,7 +211,7 @@
> cleanup(void)
> {
> 
>-	if (keep)
>+	if (keep || lockfd)
> 		flock(lockfd, LOCK_UN);
> 	else
> 		unlink(lockname);
>Only in lockf: lockf.o
>Only in lockf: test
>Only in lockf: test.sh

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Attachments on bug 262738: 232656