On Fri, Mar 01, 2024 at 08:59:01PM -0300, Paulo Alcantara wrote:
> Alexander Aring <aahringo@xxxxxxxxxx> writes:
>
> > Hi,
> >
> > On Fri, Mar 1, 2024 at 11:25 AM Paulo Alcantara <pc@xxxxxxxxxxxxx> wrote:
> >>
> >> Hi Zorro,
> >>
> >> The problem is that cifs.ko is returning -EACCES from fcntl(2) called
> >> in do_test_equal_file_lock() but it is expecting -EAGAIN to be
> >> returned, so it hangs in wait4(2):
> >>
> >> ...
> >> [pid 14846] fcntl(3, F_SETLK, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=1}) = -1 EACCES (Permission denied)
> >> [pid 14846] wait4(-1,
> >>
> >> The man page says:
> >>
> >> F_SETLK (struct flock *)
> >> Acquire a lock (when l_type is F_RDLCK or F_WRLCK) or release a
> >> lock (when l_type is F_UNLCK) on the bytes specified by the
> >> l_whence, l_start, and l_len fields of lock. If a conflicting
> >> lock is held by another process, this call returns -1 and sets
> >> errno to EACCES or EAGAIN. (The error returned in this case
> >> differs across implementations, so POSIX requires a portable ap‐
> >> plication to check for both errors.)
> >>
> >> so fcntl_lock_corner_tests should also handle -EACCES.
> >>
> >
> > yes, that is a bug in the test but in my opinion there is still an
> > issue. The mentioned fcntl(F_SETLK) above is just a sanity check to
> > print out if something is not correct and it will print out that
> > something is not correct and fails.
>
> Yes, I agree it might be a cifs.ko issue. However, it's still important
> making sure that the test exits gracefully and then report an error
> rather than hanging.
Thanks for all of you look into it!
If the C program can deal with issue (report error rather than hang),
that would be good. Or how about give the fcntl testing process a (long enough)
timeout number, to avoid it block the whole fstests test running, and report
error if it exits unnormally.
Thanks,
Zorro
>
> > The problem is that wait() below, the child processes are not
> > returning and are in a blocking state which should not be the case.
> >
> > What the test is doing is the following:
> >
> > parent:
> >
> > 1. lock(A) # should be successful to acquire
>
> Client successfully acquires it.
>
> > child:
> > thread0:
> > 2. lock(A) # should block
> > thread1:
> > 3. lock(A) # should block
>
> OK - both threads are blocked.
>
> > parent:
> >
> > 5. sleep(3) #wait until child are in blocking state of lock(A)
>
> OK.
>
> > 5. unlock(A) # both threads of the child should unlock and exit
>
> At this point, both threads are woken up and one of them acquires the
> lock and returns. The other thread gets blocked again because it finds
> a conflicting lock that was taken from the other thread. The child then
> never exits because it is waiting in pthread_join().
>
> > 6. sleep 3 # wait for pending unlock op (not really sure if it's necessary)
> > ...
> > 7. trylock(A) # mentioned sanity check
>
> Client returns -EACCES because one of the child threads acquired the
> lock.
>
> > The unlock(A) should unblock the child threads, it is important to
> > mention that this test does a lock corner test and the lock(A) in both
> > threads ends in a ->lock() call with a "struct file_lock" that has
> > mostly the same fields. We had issues with that in gfs2 and a lookup
> > function to find the right request with an async complete handler of
> > the lock operation.
>
> Alex, thanks for the explanation! As we've talked, there might be a
> missing check of fl_owner or some sort of protocol limitation while
> checking for lock conflicts.
>
> Steve, any thoughts on this?
>
