database locking woes part 2

[Ian Peters <itp ximian com>]

I've come up with another testcase to better demonstrate what I feel to
be the actual problem with database locking, at least in RPM 4.0.4. 
I'll try these programs with RPM 4.1 as soon as I can -- but this
problem is affecting me now, with deployed versions of RPM,
unfortunately.

The programs are called lock-maker and lock-breaker.  lock-maker opens
the rpm database O_RDWR, which should hold an exclusive lock, and then
sleeps for a good long time to hold that lock open.  lock-breaker
attempts to open the rpm database O_RDONLY.  If it fails, it immediately
tries to open the database again (also O_RDONLY).

To run the test, compile both programs:

gcc -o lock-maker lock-maker.c -I/usr/include/rpm -lrpm -lrpmio -lrpmdb -lpopt

gcc -o lock-breaker lock-breaker.c -I/usr/include/rpm -lrpm -lrpmio -lrpmdb -lpopt

Now, in one terminal, as root, run lock-maker.

# ./lock-maker
Opened rpm database O_RDWR

Now, to verify that the lock is held, run rpm -qa -- both as root and as
non-root, just for verification.  (The multiple runs will explain
themselves in a second.)

$ rpm -qa
error: cannot get shared lock on /var/lib/rpm/Packages
error: cannot open Packages index using db3 - Operation not permitted (1)
$ rpm -qa
error: cannot get shared lock on /var/lib/rpm/Packages
error: cannot open Packages index using db3 - Operation not permitted (1)
$ su
Password: 
# rpm -qa
error: cannot get shared lock on /var/lib/rpm/Packages
error: cannot open Packages index using db3 - Operation not permitted (1)
# rpm -qa
error: cannot get shared lock on /var/lib/rpm/Packages
error: cannot open Packages index using db3 - Operation not permitted (1)

Now, run lock-breaker:

$ ./lock-breaker
error: cannot get shared lock on /var/lib/rpm/Packages
error: cannot open Packages index using db3 - Operation not permitted (1)
Failed to open rpm database O_RDONLY
error: cannot get shared lock on /var/lib/rpm/Packages
Failed to open rpm database O_RDONLY
$ su
Password: 
# ./lock-breaker
error: cannot get shared lock on /var/lib/rpm/Packages
error: cannot open Packages index using db3 - Operation not permitted (1)
Failed to open rpm database O_RDONLY
Opened rpm database O_RDONLY

That second open really should not have succeeded.

Am I totally off-base, or missing something obvious here?

Ian

-- 
Ian Peters <itp@ximian.com>
Ximian, Inc.

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <rpm/rpmlib.h>

int
main (int argc, char **argv)
{
    rpmdb db;
    int rc;

    rpmReadConfigFiles (NULL, NULL);

    if ((rc = rpmdbOpen ("/", &db, O_RDONLY, 0644))) {
        printf ("Failed to open rpm database O_RDONLY\n");
        if ((rc = rpmdbOpen ("/", &db, O_RDONLY, 0644)))
            printf ("Failed to open rpm database O_RDONLY\n");
        else
            printf ("Opened rpm database O_RDONLY\n");
    } else
        printf ("Opened rpm database O_RDONLY\n");
}

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <rpm/rpmlib.h>

int
main (int argc, char **argv)
{
    rpmdb db;
    int rc;

    rpmReadConfigFiles (NULL, NULL);

    if ((rc = rpmdbOpen ("/", &db, O_RDWR, 0645)))
        printf ("Failed to open rpm database O_RDWR\n");
    else
        printf ("Opened rpm database O_RDWR\n");

    sleep (10000);
}