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libutil/util_lockfile: add routine to return owning pid of file lock

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Provide a mechanism via which a caller can query the pid of the process
currently holding the file lock.

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Acked-by: Steffen Eiden <seiden@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
2023-10-25 11:15:45 -04:00
committed by Steffen Eiden
parent 041e6131d1
commit af730c79a6
2 changed files with 34 additions and 0 deletions
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32
libutil/util_lockfile.c
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@@ -299,3 +299,35 @@ int util_lockfile_parent_release(char *lockfile)
{
return do_lockfile_release(lockfile, getppid());
}
/**
* Return the pid that owns the specified lockfile.
*
* @param[in] lockfile Path to the lock file
* @param[in,out] pid Buffer to place owning pid
*
* @retval 0 pid provided in buffer
* @retval !=0 Error, no pid provided
*/
int util_lockfile_peek_owner(char *lockfile, int *pid)
{
char buf[BUFSIZE];
int fd, len;
if (!lockfile || !pid)
return UTIL_LOCKFILE_ERR;
/* Open lockfile, read the owning pid if it exists */
fd = open(lockfile, O_RDONLY);
if (fd < 0)
return UTIL_LOCKFILE_ERR;
len = read(fd, buf, sizeof(buf));
close(fd);
if (len <= 0)
return UTIL_LOCKFILE_ERR;
buf[len] = 0;
*pid = atoi(buf);
return 0;
}