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Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking
From: |
Tom Lord |
Subject: |
Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking |
Date: |
Sun, 6 Jun 2004 12:35:18 -0700 (PDT) |
> From: Andrew Suffield <address@hidden>
> > I understood that
> > 1. Create nonce file
> > 2. hardlink lock file to it
> > 3. check reference count of nonce file
> > Was a reliable way of locking files across NFS. Is this not the case?
> FSVO "reliable". It's non-atomic - it is not the case that precisely
> one process will get the lock. Specifically, it's possible that no
> processes will get the lock.
No it isn't.
> If you get two clients trying to claim
> the lock at once, they can get into a mutual busy loop, repeatedly
> trying and failing, so you have to rely on random wait states to break
> this loop. This can be quite impressively slow.
While the lock file doesn't exist, the first `link(2)' call made for
it wins the lock.
> It also requires manual intervention to break stale locks
> safely.
_That_ is the real problem. Unless the intervention is able to
include "kill all client processes that might _think_ they hold this
lock" you simply can't break stale locks (of this variety) safely.
-t
- Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, (continued)
- [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Robin Farine, 2004/06/04
- Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Jan Hudec, 2004/06/04
- Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Robin Farine, 2004/06/04
- Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Andrew Suffield, 2004/06/04
- Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Tom Lord, 2004/06/06
- Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Jan Hudec, 2004/06/06
- Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Tom Lord, 2004/06/07
Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking,
Tom Lord <=
Re: [Gnu-arch-users] Re: [BUG] FEATURE PLANS: revlib locking, Tom Lord, 2004/06/06