Date: Thu, 4 Oct 2007 18:29:25 -0700 (PDT) From: Jeff Roberson <jroberson@chesapeake.net> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/fs/devfs devfs_vnops.c src/sys/fs/fifofs fifo_vnops.c src/sys/kern uipc_usrreq.c vfs_vnops.c src/sys/vm vnode_pager.c Message-ID: <20071004182759.U912@10.0.0.1> In-Reply-To: <200710041219.13202.jhb@freebsd.org> References: <200710032106.l93L65bv095725@repoman.freebsd.org> <20071003164642.B615@10.0.0.1> <200710041219.13202.jhb@freebsd.org>
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On Thu, 4 Oct 2007, John Baldwin wrote: > On Wednesday 03 October 2007 07:48:00 pm Jeff Roberson wrote: >> On Wed, 3 Oct 2007, John Baldwin wrote: >> >>> jhb 2007-10-03 21:06:05 UTC >>> >>> FreeBSD src repository >>> >>> Modified files: (Branch: RELENG_6) >>> sys/fs/devfs devfs_vnops.c >>> sys/fs/fifofs fifo_vnops.c >>> sys/kern uipc_usrreq.c vfs_vnops.c >>> sys/vm vnode_pager.c >>> Log: >>> MFC: Always use an exclusive lock on the leaf vnode during an open() when >>> shared lookups are enabled. This closes a few races including a race > where >>> concurrent opens of a fifo could result in different v_fifoinfo > structures >>> in different threads. >> >> Long term we should really look for a better solution to this problem. >> There are a number of was to improve snapshots in ffs by fixing shared >> locking. > > I don't disagree. The fifo case can be fixed easily enough in the fifo code > by using fifo_mtx to protect v_fifoinfo perhaps (or doing an upgrade on the > vnode lock?), but for the MFC I didn't want to have to fix each of the races > with open(2). Probably better to fix it more properly in HEAD first. Definitely someting for head. Were there any others that you ran into besides v_fifoinfo? We should audit this more closely anyhow. I have been reluctant to push too much shared locking into VFS because it's not been so carefully studied. Jeff > > -- > John Baldwin >
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