Hi.
We're testing the most recent ZFS version from OpenSolaris ported to
FreeBSD. Kris (CCed) observed strange situation. In function arc_read()
he had a panic on assertion that we try to unlock a lock which is not
beeing held:
rw_enter(&pbuf->b_hdr->b_datalock, RW_READER);
err = arc_read_nolock(pio, spa, bp, done, private, priority,
flags, arc_flags, zb);
rw_exit(&pbuf->b_hdr->b_datalock); <--- THIS ONE
The only possiblity was that b_hdr for pbuf was changed somewhere. We
diagnozed this further and the b_hdr field is changed in arc_release()
function, here:
buf->b_hdr = nhdr;
Backtrace for this change is the following:
arc_release() at arc_release+0x4ec
dbuf_write() at dbuf_write+0x26b
dbuf_sync_list() at dbuf_sync_list+0x3eb
dbuf_sync_list() at dbuf_sync_list+0x17f
dbuf_sync_list() at dbuf_sync_list+0x17f
dbuf_sync_list() at dbuf_sync_list+0x17f
dbuf_sync_list() at dbuf_sync_list+0x17f
dbuf_sync_list() at dbuf_sync_list+0x17f
dbuf_sync_list() at dbuf_sync_list+0x17f
dnode_sync() at dnode_sync+0x9bd
dmu_objset_sync() at dmu_objset_sync+0x120
dsl_pool_sync() at dsl_pool_sync+0x72
spa_sync() at spa_sync+0x2f3
txg_sync_thread() at txg_sync_thread+0x2cd
Do you have any ideas how to fix it? Kris has a way to reproduce it in
his environment and I'm sure he could try a patch, if you could provide
one.
--
Pawel Jakub Dawidek http://www.wheel.pl
pjd at FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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