Date: Sun, 6 Oct 2013 08:22:27 -0700 From: Matthew Fleming <mdf@FreeBSD.org> To: "Julian H. Stacey" <jhs@berklix.com> Cc: "current@freebsd.org Current" <current@freebsd.org> Subject: Re: lock order reversals on 10.0-ALPHA4 Message-ID: <CAMBSHm8K5vSFe9qkhSpd7PQVpwV_FSDoVqNyHMAU3y5XFJCjNQ@mail.gmail.com> In-Reply-To: <201310061344.r96DiLnN059117@fire.js.berklix.net> References: <201310061344.r96DiLnN059117@fire.js.berklix.net>
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On Sun, Oct 6, 2013 at 6:44 AM, Julian H. Stacey <jhs@berklix.com> wrote: > With: > FreeBSD lapr.js.berklix.net 10.0-ALPHA4 FreeBSD 10.0-ALPHA4 #0 > r255933: Sun Sep 29 02:50:54 UTC 2013 > root@snap.freebsd.org:/usr/obj/usr/src/sys/GENERIC amd64 > > At boot dmesg shows several lock order reversals, eg > > ------ > Trying to mount root from ufs:/dev/ad4s2a [rw]... > ipfw2 (+ipv6) initialized, divert loadable, nat loadable, default to deny, > logging disabled > lock order reversal: > 1st 0xfffffe00a6e26b48 bufwait (bufwait) @ > /usr/src/sys/kern/vfs_bio.c:3059 > 2nd 0xfffff80005cf8400 dirhash (dirhash) @ > /usr/src/sys/ufs/ufs/ufs_dirhash.c:284 > KDB: stack backtrace: > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame > 0xfffffe00c8f3d3f0 > kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe00c8f3d4a0 > witness_checkorder() at witness_checkorder+0xd23/frame 0xfffffe00c8f3d530 > _sx_xlock() at _sx_xlock+0x75/frame 0xfffffe00c8f3d570 > ufsdirhash_add() at ufsdirhash_add+0x3b/frame 0xfffffe00c8f3d5b0 > ufs_direnter() at ufs_direnter+0x688/frame 0xfffffe00c8f3d670 > ufs_makeinode() at ufs_makeinode+0x573/frame 0xfffffe00c8f3d830 > ufs_symlink() at ufs_symlink+0x32/frame 0xfffffe00c8f3d880 > VOP_SYMLINK_APV() at VOP_SYMLINK_APV+0xf0/frame 0xfffffe00c8f3d8b0 > kern_symlinkat() at kern_symlinkat+0x23e/frame 0xfffffe00c8f3dae0 > amd64_syscall() at amd64_syscall+0x265/frame 0xfffffe00c8f3dbf0 > Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe00c8f3dbf0 > --- syscall (57, FreeBSD ELF64, sys_symlink), rip = 0x800888ffa, rsp = > 0x7fffffffca58, rbp = 0x7fffffffdc10 --- > lock order reversal: > 1st 0xfffff800881b9d50 ufs (ufs) @ /usr/src/sys/kern/vfs_mount.c:851 > 2nd 0xfffff800881b99a0 devfs (devfs) @ /usr/src/sys/kern/vfs_subr.c:2099 > KDB: stack backtrace: > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame > 0xfffffe00c8ed93d0 > kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe00c8ed9480 > witness_checkorder() at witness_checkorder+0xd23/frame 0xfffffe00c8ed9510 > __lockmgr_args() at __lockmgr_args+0x6f2/frame 0xfffffe00c8ed9640 > vop_stdlock() at vop_stdlock+0x3c/frame 0xfffffe00c8ed9660 > VOP_LOCK1_APV() at VOP_LOCK1_APV+0xf5/frame 0xfffffe00c8ed9690 > _vn_lock() at _vn_lock+0xab/frame 0xfffffe00c8ed9700 > vget() at vget+0x70/frame 0xfffffe00c8ed9750 > devfs_allocv() at devfs_allocv+0xfd/frame 0xfffffe00c8ed97a0 > devfs_root() at devfs_root+0x43/frame 0xfffffe00c8ed97d0 > vfs_donmount() at vfs_donmount+0x115e/frame 0xfffffe00c8ed9aa0 > sys_nmount() at sys_nmount+0x72/frame 0xfffffe00c8ed9ae0 > amd64_syscall() at amd64_syscall+0x265/frame 0xfffffe00c8ed9bf0 > Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe00c8ed9bf0 > --- syscall (378, FreeBSD ELF64, sys_nmount), rip = 0x800a9dd7a, rsp = > 0x7fffffffccb8, rbp = 0x7fffffffd220 --- > ---- > > Those two LORs are well-known and at least the fist is definitely a false positive. They're rather tricky to fix; there's been previous discussion. The first one is #261 at http://sources.zabbadoz.net/freebsd/lor.html . The second one is probably #280. Cheers, matthew
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