This is 1.5.25 but also happens on earlier versions.
It would appear that placing a shared read lock
on a file open for input/output is preventing the
the process itself from writing.
Consider -
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int
main ()
{
int fd;
struct flock lock;
errno = 0;
fd = open ("TESTFILE", O_CREAT | O_TRUNC | O_WRONLY, 0777);
printf("Open for write - Errno %d\n", errno);
if (fd >= 0) {
errno = 0;
if (write (fd, "TESTtest", 8) != 8) {
printf ("Write error - %d\n", errno);
close (fd);
return 1;
}
errno = 0;
close (fd);
printf("Close after write - Errno %d\n", errno);
}
fd = open ("TESTFILE", O_RDWR, 0);
printf("Open for I/O - Errno %d\n", errno);
if (fd < 0) {
return 1;
}
memset (&lock, 0, sizeof (struct flock));
lock.l_type = F_RDLCK;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0;
errno = 0;
if (fcntl (fd, F_SETLK, &lock) < 0) {
printf ("Lock error - %d\n", errno);
close (fd);
return 1;
}
errno = 0;
if (write (fd, "test", 4) != 4) {
printf ("Write I/O error - %d\n", errno);
}
memset (&lock, 0, sizeof (struct flock));
lock.l_type = F_UNLCK;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0;
errno = 0;
if (fcntl (fd, F_SETLK, &lock) < 0) {
printf ("Unlock error - %d\n", errno);
close (fd);
return 1;
}
close (fd);
return 0;
}
This always prodcues -
Write I/O error - 13
ie. EACCES
Margit
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