Date: Thu, 4 Oct 2007 12:19:12 -0400 From: John Baldwin <jhb@freebsd.org> To: Jeff Roberson <jroberson@chesapeake.net> 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: <200710041219.13202.jhb@freebsd.org> In-Reply-To: <20071003164642.B615@10.0.0.1> References: <200710032106.l93L65bv095725@repoman.freebsd.org> <20071003164642.B615@10.0.0.1>
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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. -- John Baldwin
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