Re: [PATCH 3/3] Add timeout feature

On Wed 2008-07-09 09:08:07, Miklos Szeredi wrote:
On Tue, 8 Jul 2008, Arjan van de Ven wrote:
I tihnk the idea there is

freeze . do the snapshot op . unfreeze . make backup of snapshot

Ah, so then my proposal would become

run_frozen mountpoint do-snapshot
do-backup
release-snapshot

and if they are afraid of deadlocks they can just implement the
timeout in userspace:

run_frozen -t timeout mountpoint do-snapshot

'run_frozen' can be a trivial 30 line app, that can be guaranteed not
to deadlock.

Userland apps can be swapped out and need kernel memory allocations
during syscalls.

I bet even sleep(30) uses kmalloc internally.

So yes, even trivial applications can deadlock.

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