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libutil/util_lockfile: allow for custom lock wait/retry time

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The default values for repeated attempts at acquiring a file lock created
by util_lockfile are on the order of seconds.  Let's leave this the
default, but allow for a caller to specify smaller values by adding
cw (custom_wait) functions and by switching from using sleep to usleep.

Reviewed-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
This commit is contained in:
Matthew Rosato
2024-04-11 14:23:23 -04:00
committed by Steffen Eiden
parent 0a01719477
commit f5f806af06
2 changed files with 58 additions and 9 deletions
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4
include/lib/util_lockfile.h
View File

@@ -18,7 +18,11 @@
#define UTIL_LOCKFILE_ERR 4 /* Other, unexpected error conditions */
int util_lockfile_lock(char *lockfile, int retries);
int util_lockfile_lock_cw(char *lockfile, int retries, unsigned int waitinc,
unsigned int maxwait);
int util_lockfile_parent_lock(char *lockfile, int retries);
int util_lockfile_parent_lock_cw(char *lockfile, int retries,
unsigned int waitinc, unsigned int maxwait);
int util_lockfile_release(char *lockfile);
int util_lockfile_parent_release(char *lockfile);

63
libutil/util_lockfile.c
View File

@@ -25,8 +25,8 @@
#include "lib/util_panic.h"
#define WAITPID 120 /* Time to wait for pid to be written */
#define WAITINC 5 /* Additional time to wait each retry */
#define MAXWAIT 60 /* Maximum wait between retries */
#define DEF_WAITINC_US 5000000 /* Additional time to wait each retry */
#define DEF_MAXWAIT_US 60000000 /* Maximum wait between retries */
#define BUFSIZE 40 /* Buffer must be large enough to fit pid string */
/**
@@ -133,15 +133,20 @@ static int handle_stale_lock(char *lockfile)
*
* @param[in] lockfile Path to the lock file
* @param[in] retries Number of times to retry if lock fails initially
* @param[in] waitinc How many micro-seconds to extend wait time before
* additional retry
* @param[in] maxwait Maximum wait time before retry
* @param[in] pid PID to use for lock ownership
*
* @retval 0 Lock created with PID as owner
* @retval !=0 Lock was not created
*/
static int do_lockfile_lock(char *lockfile, unsigned int retries, int pid)
static int do_lockfile_lock(char *lockfile, unsigned int retries, int pid,
unsigned int waitinc, unsigned int maxwait)
{
int fd, plen, len, rc = 0, snooze = 0;
unsigned int tries = retries + 1;
int fd, plen, len, rc = 0;
unsigned int snooze = 0;
char buf[BUFSIZE];
char *tpath;
@@ -190,9 +195,9 @@ static int do_lockfile_lock(char *lockfile, unsigned int retries, int pid)
if (rc != 0) {
tries--;
if (tries > 0) {
snooze += WAITINC;
snooze = (snooze > MAXWAIT) ? MAXWAIT : snooze;
sleep(snooze);
snooze += waitinc;
snooze = (snooze > maxwait) ? maxwait : snooze;
usleep(snooze);
}
}
} while (tries > 0);
@@ -255,7 +260,27 @@ static int do_lockfile_release(char *lockfile, int pid)
*/
int util_lockfile_lock(char *lockfile, int retries)
{
return do_lockfile_lock(lockfile, retries, getpid());
return do_lockfile_lock(lockfile, retries, getpid(), DEF_WAITINC_US,
DEF_MAXWAIT_US);
}
/**
* Attempt to create a lockfile owned by this process at the specified path
* using a custom wait/retry time.
*
* @param[in] lockfile Path to the lock file
* @param[in] retries Number of times to retry if lock fails initially
* @param[in] waitinc How many micro-seconds to extend wait time before
* additional retry
* @param[in] maxwait Maximum wait time before retry
*
* @retval 0 Lock created
* @retval !=0 Lock was not created
*/
int util_lockfile_lock_cw(char *lockfile, int retries, unsigned int waitinc,
unsigned int maxwait)
{
return do_lockfile_lock(lockfile, retries, getpid(), waitinc, maxwait);
}
/**
@@ -270,7 +295,27 @@ int util_lockfile_lock(char *lockfile, int retries)
*/
int util_lockfile_parent_lock(char *lockfile, int retries)
{
return do_lockfile_lock(lockfile, retries, getppid());
return do_lockfile_lock(lockfile, retries, getppid(), DEF_WAITINC_US,
DEF_MAXWAIT_US);
}
/**
* Attempt to create a lockfile owned by the parent of this process at the
* specified path using a custom wait/retry time.
*
* @param[in] lockfile Path to the lock file
* @param[in] retries Number of times to retry if lock fails initially
* @param[in] waitinc How many micro-seconds to extend wait time before
* additional retry
* @param[in] maxwait Maximum wait time before retry
*
* @retval 0 Lock created
* @retval !=0 Lock was not created
*/
int util_lockfile_parent_lock_cw(char *lockfile, int retries,
unsigned int waitinc, unsigned int maxwait)
{
return do_lockfile_lock(lockfile, retries, getppid(), waitinc, maxwait);
}
/**