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Re: CVS commit: src/external/cddl/osnet/dist/uts/common/fs/zfs

On Oct,Thursday 29 2009, at 8:15 PM, David Laight wrote:

On Wed, Oct 28, 2009 at 11:44:51PM +0000, Adam Hamsik wrote:
Module Name:    src
Committed By:   haad
Date:           Wed Oct 28 23:44:51 UTC 2009

Modified Files:
src/external/cddl/osnet/dist/uts/common/fs/zfs: zfs_vnops.c zfs_znode.c

Log Message:
Add workaround about zfs vnode reclaiming deadlock by checking if we don't ehld ZFS_MUTEX_OBJ already. If we can lock OBJ_MUTEX deffer execution of zfs_zinactive to taskq. Code was inspired by FreeBSD zfs_freebsd_reclaim.

This doesn't sound right at all ...

If the 'If we can lock OBJ_MUTEX' test is a try_mutex_enter() then
it may fail because another lwp owns it ...
I hope it is only the checkin comment that is inverted!

There are 3 option which can happen

1) Our lwp already holds mutex
2) mutex is not held at all
3) Another LWP holds it

In case 1 we can call reclaim vnode, in case 2 we lock it with try_mutex_enter and reclaim it and in case 3 we use taskq for reclaiming of vnode.


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