dir_lookup, locking and EINTR

Hello,

We are still facing some ext2fs hangs sometimes, and I got an
interesting backtrace today:

Thread 94 (thread 348.94):
#0 0x010d753c in mach_msg_trap () from /lib/libc.so.0.3
#1 0x010d7cc9 in mach_msg () from /lib/libc.so.0.3
#2 0x010a3630 in cproc_block ()
at /
#3 0x010a3d1a in __mutex_lock_solid (ptr CCCC 0x8123c6c )
at /
#4 0x0104a1e9 in diskfs_release_peropen (po=0x8242640)
at /
#5 0x0104a402 in diskfs_protid_rele (arg=0x81d0818)
at /
#6 0x010aa912 in _ports_complete_deallocate (pi=0x81d0818)
at /
#7 0x010a9421 in ports_port_deref (portstruct=0x81d0818)
at /
#8 0x01038825 in diskfs_S_dir_lookup (dircred=0x80e9698,
path=0x1aedf4c "@test", flags=262154=NNBLCK|WRNLY|EXLCK, mode=0, retry=0x1aebf44,
retryname=0x1aebf4c "", returned_port=0x1aec350,
returned_port_poly=0x1aebe48)
at /

dir-lookup.c:478 is as follows:

469 if (! error)
470 {
471 if (flags & EXLCK)
472 error = fshelp_acquire_lock (&np->userlock, &newpi->po->lock_status,
473 &np->lock, LCK_EX);
474 else if (flags & SHLCK)
475 error = fshelp_acquire_lock (&np->userlock, &newpi->po->lock_status,
476 &np->lock, LCK_SH);
477 if (error)
478 ports_port_deref (newpi); /* Get rid of NEWPI. */
479 }

i.e. someone tried to open @test exclusively, but it failed (EINTR),
and thus we drop newpi. The problem is that since that's the last
reference, it cals _ports_complete_deallocate, which ends up calling
diskfs_release_peropen which tries to acquire the lock on np, which we
_already_ have, thus the deadlock, which quickly propagates to the /.

It looks like we have the same problem with diskfs_create_protid().

Since in case of an error we don't return a locked np, I guess the
correct fix is as attached to this mail?

Samuel