Package: chiark-utils-bin
Version: 4.2.0
Severity: wishlist
Tags: upstream patch
Hi,
I wanted a timeout option to with-lock-ex. The attached patch provides
this - you can see -t <secs> after -q or -f and with-lock-ex will then
wait that long while trying to get the lock before quitting.
I have built and tested the attached patch against the current master
branch in git.
-- System Information:
Debian Release: 7.11
APT prefers oldstable-updates
APT policy: (500, 'oldstable-updates'), (500, 'oldstable')
Architecture: i386 (i686)
Kernel: Linux 3.2.0-4-686-pae (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages chiark-utils-bin depends on:
ii libc6 2.13-38+deb7u11
Versions of packages chiark-utils-bin recommends:
ii libc6 2.13-38+deb7u11
ii libgmp10 2:5.0.5+dfsg-2
ii libnettle4 2.4-3+deb7u1
Versions of packages chiark-utils-bin suggests:
ii libx11-6 2:1.5.0-1+deb7u4
-- no debconf information
diff --git a/cprogs/with-lock-ex.c b/cprogs/with-lock-ex.c
index 2b7b45b..560711f 100644
--- a/cprogs/with-lock-ex.c
+++ b/cprogs/with-lock-ex.c
@@ -2,7 +2,7 @@
* File locker
*
* Usage:
- * with-lock-ex -<mode> <lockfile> <command> <args>...
+ * with-lock-ex -<mode> [-t <secs>] <lockfile> <command> <args>...
* with-lock-ex -l <lockfile>
*
* modes are
@@ -13,6 +13,11 @@
* or "write <pid>"; lockfile opened for reading;
* no command may be specified)
*
+ * if -t is specified, then with-lock-ex will wait for up to <secs>
+ * seconds to acquire the lock, and then fail or silently do nothing
+ * (depending on whether -f or -q is specified). You cannot specify
+ * a timeout for modes l or w
+ *
* with-lock-ex will open and lock the lockfile for writing and
* then feed the remainder of its arguments to exec(2); when
* that process terminates the fd will be closed and the file
@@ -32,6 +37,10 @@
#include <unistd.h>
#include <string.h>
#include <sys/stat.h>
+#include <limits.h>
+#include <time.h>
+#include <signal.h>
+#include <sys/time.h>
static const char *cmd;
@@ -42,12 +51,22 @@ static void fail(const char *why) {
exit(255);
}
+volatile int alarmed = 0;
+
+static void alrm_handler(int signum) {
+ alarmed = 1;
+}
+
int main(int argc, char **argv) {
int fd, mode, um;
struct stat stab, fstab;
- long cloexec;
+ long cloexec, secs=-1;
struct flock fl;
const char *p;
+ char *endptr;
+ time_t tstart=0, tend=0;
+ struct sigaction siga, oldsiga;
+ struct itimerval itv;
if (argc >= 3 && !strcmp((p= strrchr(argv[0],'/')) ? ++p : argv[0], "with-lock")) {
mode= 'f';
@@ -56,7 +75,7 @@ int main(int argc, char **argv) {
&& mode != 'l') ||
(mode != 'l' && argc < 4) ||
(mode == 'l' && argc != 3)) {
- fputs("usage: with-lock-ex -w|-q|-f <lockfile> <command> <args>...\n"
+ fputs("usage: with-lock-ex -w|-q|-f [-t <secs>] <lockfile> <command> <args>...\n"
" with-lock-ex -l <lockfile>\n"
" with-lock <lockfile> <command> <args>...\n",
stderr);
@@ -64,6 +83,39 @@ int main(int argc, char **argv) {
} else {
argv++; argc--;
}
+ if (0 == strncmp(argv[1],"-t",2)) {
+ errno = 0;
+ secs = strtol(argv[2], &endptr, 0);
+ if ((errno == ERANGE && (secs == LONG_MAX || secs == LONG_MIN))
+ || (errno !=0 && secs == 0)) {
+ fail("parsing timeout value");
+ }
+ if (secs <= 0) {
+ fputs("timeout value must be greater than zero.\n",
+ stderr);
+ exit(255);
+ }
+ tstart = time(NULL); if (tstart==(time_t)-1) fail("getting current time");
+ if (mode=='l' || mode=='w') {
+ fputs("-t only allowed with -q or -f.\n", stderr);
+ exit(255);
+ }
+ argv+= 2; argc-= 2;
+ if (argc < 2) {
+ fputs("Insufficient arguments following -t\n"
+ "Usage: with-lock-ex -f|q -t <secs> <lockfile> <command> <args>...\n",
+ stderr);
+ exit(255);
+ }
+ /*Install SIGALRM handler, and set a timer for secs seconds from now*/
+ memset(&siga,0,sizeof(siga));
+ siga.sa_handler=alrm_handler;
+ if (sigaction(SIGALRM,&siga,&oldsiga)) fail("Installing SIGALRM handler");
+ memset(&itv,0,sizeof(itv));
+ itv.it_value.tv_sec=secs;
+ if (setitimer(ITIMER_REAL,&itv,NULL)) fail("Setting timer");
+ }
+
cmd= argv[2];
um= umask(0777); if (um==-1) fail("find umask");
if (umask(um)==-1) fail("reset umask");
@@ -82,9 +134,21 @@ int main(int argc, char **argv) {
fl.l_len= mode=='l' ? 0 : 1;
if (fcntl(fd,
mode=='l' ? F_GETLK :
- mode=='w' ? F_SETLKW :
+ mode=='w' || secs > 0 ? F_SETLKW :
F_SETLK,
&fl) != -1) break;
+ if (alarmed==1) {
+ tend = time(NULL); if (tend==(time_t)-1) fail("getting current time");
+ if (tend-tstart >= secs) {
+ if (mode=='q') exit(0);
+ else {
+ fprintf(stderr,
+ "with-lock-ex %s: timer expired while trying to acquire lock\n",
+ cmd);
+ exit(255);
+ }
+ } else alarmed=0;
+ }
if (mode=='q' &&
(errno == EAGAIN || errno == EWOULDBLOCK || errno == EBUSY))
exit(0);
@@ -102,6 +166,11 @@ int main(int argc, char **argv) {
if (ferror(stdout)) fail("print to stdout\n");
exit(0);
}
+ if (secs > 0) {
+ itv.it_value.tv_sec=0;
+ if (setitimer(ITIMER_REAL,&itv,NULL)) fail("Clearing timer");
+ if (sigaction(SIGALRM,&oldsiga,NULL)) fail("Restoring SIGALRM handler");
+ }
if (fstat(fd, &fstab)) fail("could not fstat lock fd");
if (stat(argv[1], &stab)) {
