Date: Thu, 18 Dec 2008 23:06:34 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: pluknet <pluknet@gmail.com> Cc: freebsd-current <freebsd-current@freebsd.org> Subject: Re: LOR between nfs and proctree Message-ID: <20081218210634.GL2038@deviant.kiev.zoral.com.ua> In-Reply-To: <a31046fc0812171443m42fa11cfi66cc5fefb4efcb63@mail.gmail.com> References: <a31046fc0812171443m42fa11cfi66cc5fefb4efcb63@mail.gmail.com>
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--vRyMahX6VF+pdQvX Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Dec 18, 2008 at 01:43:38AM +0300, pluknet wrote: > I didn't find this LOR in archives and don't know if this is known > one, so I'm posting it here. >=20 > lock order reversal: > 1st 0xc5ea37ac nfs (nfs) @ /usr/src/sys/kern/vfs_vnops.c:531 > 2nd 0xc0889090 proctree (proctree) @ /usr/src/sys/kern/kern_fork.c:311 > KDB: stack backtrace: > db_trace_self_wrapper(c07fb0cf,e7d1f8cc,c05d79e5,4,c07f662d,...) at > db_trace_self_wrapper+0x26 > kdb_backtrace(4,c07f662d,c54fcad8,c54f6068,e7d1f928,...) at kdb_backtrace= +0x29 > _witness_debugger(c07fdd7f,c0889090,c07f702d,c54f6068,c07f3e44,...) at > _witness_debugger+0x25 > witness_checkorder(c0889090,1,c07f3e44,137,0,...) at witness_checkorder+0= x839 > _sx_slock(c0889090,0,c07f3e44,137,0,...) at _sx_slock+0x85 > fork1(c0887530,60034,0,e7d1f9c0,c07f662d,...) at fork1+0x2cd > kproc_create(c06dc780,c09f8920,0,40000,0,...) at kproc_create+0x47 > nfs_nfsiodnew(c09f8f70,0,c080e39a,553,0,...) at nfs_nfsiodnew+0xc5 > nfs_asyncio(c5c024e8,d952b670,c5af0000,c5abdd80,0,...) at nfs_asyncio+0x3= a5 > nfs_bioread(c5ea3754,e7d1fc58,20000,c5af0000,e7d1fba0,...) at nfs_bioread= +0x788 > nfs_read(e7d1fbc8,c5abdd80,c5e63968,c5abdd80,e7d1fbe8,...) at nfs_read+0x= 44 > VOP_READ_APV(c085d360,e7d1fbc8,c0805cb8,213,c5abde24,...) at VOP_READ_APV= +0xa5 > vn_read(c5e63968,e7d1fc58,c5af0000,0,c5abdd80,...) at vn_read+0x1ee > dofileread(e7d1fc58,ffffffff,ffffffff,0,c5e63968,...) at dofileread+0x96 > kern_readv(c5abdd80,4,e7d1fc58,e7d1fc78,1,...) at kern_readv+0x58 > read(c5abdd80,e7d1fcf8,c,c07fe5a8,c083f5c8,...) at read+0x4f > syscall(e7d1fd38) at syscall+0x2a3 > Xint0x80_syscall() at Xint0x80_syscall+0x20 > --- syscall (3, FreeBSD ELF32, read), eip =3D 0x281c7f93, esp =3D > 0xbfbfeaec, ebp =3D 0xbfbfec28 --- It is more or less known, nfs may create new nfsiod while holding vnode lock. Severity of the issue lowered with removal of the single-threading from the fork(), but it is still real. Workaround is to create required amount of nfsiod in advance. --vRyMahX6VF+pdQvX Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAklKu1oACgkQC3+MBN1Mb4g6YwCfY9zIWp0Zksu9igKVpm4M2jK+ XDAAn3kciBkJ9TsQIbt5h+zuwYQ/qC9r =laxd -----END PGP SIGNATURE----- --vRyMahX6VF+pdQvX--
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