[Info-vax] K-mutex

[Pierre]

On Dec 15, 1:11 pm, VAXman-  @SendSpamHere.ORG wrote:
> In article <99c1d545-9fcb-45ed-b8e0-2e1f053ed... at z17g2000vbe.googlegroups.com>, Jose Baars <peutba... at googlemail.com> writes:
>
> >On Dec 14, 11:18=A0pm, Pierre <pierre.... at gmail.com> wrote:
> >> On Dec 14, 7:43=A0pm, koeh... at eisner.nospam.encompasserve.org (Bob
>
> >> the easiest way to emulate semaphores with the DLM is to use a lock
> >> with a value block. this method is not fault-tolerant but neither are
> >> semaphores (if a process crash before freeing the resource slot, this
> >> slot may be totally =A0lost).
>
> >Wouldn't the crash of a process holding an EX lock cause the lock to
> >be released
> >or freed by a dead lock search?
>
> Process rundown will clean-up locks.  However, if there is some value to
> the contents of the LVB in the locking scheme, it could still leave your
> resource stranded.

and the SYS$ENQ doc says:

The following events can cause the lock value block to become invalid:
•    If any process holding a protected write or exclusive mode lock
on a resource
is terminated abnormally or exits before explicitly dequeuing the lock
or
converting it to a lover-level lock mode, the lock value block becomes
invalid.

Pierre