Date: Sun, 10 Aug 1997 14:17:13 -0700 (PDT) From: andrew@erlenstar.demon.co.uk To: freebsd-gnats-submit@FreeBSD.ORG Subject: kern/4265: Panic in dsinit when multiple FreeBSD slices exist on one disk Message-ID: <199708102117.OAA15679@hub.freebsd.org> Resent-Message-ID: <199708102120.OAA15856@hub.freebsd.org>
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>Number: 4265 >Category: kern >Synopsis: Panic in dsinit when multiple FreeBSD slices exist on one disk >Confidential: no >Severity: serious >Priority: high >Responsible: freebsd-bugs >State: open >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Sun Aug 10 14:20:01 PDT 1997 >Last-Modified: >Originator: Andrew Gierth >Organization: >Release: 2.2-STABLE >Environment: FreeBSD erlenstar.demon.co.uk 2.2-STABLE FreeBSD 2.2-STABLE #0: Sun Aug 10 21:21:51 BST 1997 root@:/usr/src/sys/compile/LOCAL i386 >Description: System panics when fsck -p is invoked (if kernel built with DIAGNOSTIC) or shortly thereafter (if not built with DIAGNOSTIC). This occurs if multiple FreeBSD slices are used on a disk (other than the root disk?). The panic is due to a race condition in dsopen/dsinit; dsopen is being called simultaneously from two of the fsck subprocesses, and this sequence results: dsopen() called; dsopen() calls dsinit(); dsinit() allocates dummy slice table and stores its address; a context switch occurs dsopen() called again; dsisopen() is false at this point, but a slice table for the unit is present (the dummy one allocated above) so dsgone() is called, freeing the slice table; dsinit() resumes, and calls free() on the dummy slice table to replace it with the real one, but panics as it has already been freed. >How-To-Repeat: timing dependent, so it might be hard, but creating a filesystem on a second FreeBSD slice on a non-root disk and adding a suitable entry to /etc/fstab, then rebooting and running fsck -p, does it every time for me. >Fix: dsopen needs to be protected against simultaneous calls for multiple slices on the same physical unit. >Audit-Trail: >Unformatted:
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