This is a known bug: 6732083 arc_read() panic: rw_exit: lock not held
with a known cause. The fix you suggest works, but it rather ugly. We are working on a fix now. -Mark Pawel Jakub Dawidek wrote: > On Tue, Jul 29, 2008 at 12:41:16PM +0200, Pawel Jakub Dawidek wrote: >> 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; > [...] > > We have a simple test case to reproduce that and a patch that seems to > work for us. I don't really understand the code well enough to be able > to prepare the right fix. > > The patch is here: > > http://people.freebsd.org/~pjd/patches/arc.patch > > Script to reproduce it: > > #!/bin/sh > fs=tank/$$ > while true; do > zfs clone tank/boom at boom $fs > find /$fs > /dev/null > zfs destroy $fs > done > > To use it, you first need to create pool tank and tank/boom dataset, > then put some files into /tank/boom/ (we had FreeBSD source tree in > there), then take a snapshot tank/boom at boom and: > > # cp boom.sh /tank/ > # cd /tank > # ./boom.sh &; ./boom.sh &; ./boom.sh &; ./boom.sh & > > You'll need SMP machine to reproduce that. We tried to reproduce it on > recent OpenSolaris, but we have only one CPU in there and we weren't > able to reproduce it. Maybe it is FreeBSD-specific problem, but it > doesn't look like that. Could you guys at least try to reproduce it on > some SMP OpenSolaris machine? > > Thanks in advance! > > > > ------------------------------------------------------------------------ > > _______________________________________________ > zfs-code mailing list > zfs-code at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-code
