On Fri, Apr 12, 2019 at 04:23:35PM +0100, Edward Napierala wrote: > On Fri, 12 Apr 2019 at 16:20, Konstantin Belousov <kostik...@gmail.com> wrote: > > > > On Fri, Apr 12, 2019 at 03:28:26PM +0100, Edward Napierala wrote: > > > On Thu, 11 Apr 2019 at 17:26, Conrad Meyer <c...@freebsd.org> wrote: > > > > > > > > Hi Edward, > > > > > > > > I have a question about this change below. > > > > > > > > On Thu, Apr 11, 2019 at 4:22 AM Edward Tomasz Napierala > > > > <tr...@freebsd.org> wrote: > > > > > > > > > > Author: trasz > > > > > Date: Thu Apr 11 11:21:45 2019 > > > > > New Revision: 346120 > > > > > URL: https://svnweb.freebsd.org/changeset/base/346120 > > > > > > > > > > Log: > > > > > Use shared vnode locks for the ELF interpreter. > > > > > > [..] > > > > > > > On the one hand, perhaps VOP_IS_TEXT() is rarely false for common > > > > interpreters anyway. On the other hand, there is sort of a > > > > renaissance of static linking happening. So maybe the thought is, > > > > !VOP_IS_TEXT is likely to be rare, and LK_UPGRADE success even more > > > > rare, so why bother writing additional code for it? > > > > > > Konstantin already answered to most of the points, but regarding > > > this one: that's exactly the case. In a typical case, the number of times > > > this code path will be executed is zero. I'd expect one - when running > > > dynamically linked ELF binary for the first time - but for some reason in > > > that case lookup() returns with the exclusive vnode lock already held. > > > > This is strange. Which filesystem do you use ? > > UFS. I see. UFS has to use exclusive locking in ffs_vget() when the vnode is created, i.e. de-facto when inode is read from the volume. See the manipulations of flags in ffs_vgetf() right after vfs_hash_get() was unable to find a cached vnode.
But if you just installed new /libexec/ld-elf.so.1, or the binary uses some other interpreter which was written right before the execve(2) call, then vnode most likely is still cached and is returned shared-locked. Use this scenario to actually test the code. _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
