Messages in this thread | | | Date | Thu, 15 Mar 2012 20:42:35 +0000 | From | Al Viro <> | Subject | Re: [patch 0/5] seqlock consolidation |
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On Thu, Mar 15, 2012 at 08:17:12PM +0100, Thomas Gleixner wrote: > > + hits += replace_path(&fs->root, old_root, new_root); > > + hits += replace_path(&fs->pwd, old_root, new_root); > > Wouldn't it be simpler to just do: > > + count += replace_path(&fs->root, old_root, new_root); > + count += replace_path(&fs->pwd, old_root, new_root); > > > + write_seqcount_end(&fs->seq); > > + while (hits--) { > > count++; > > Instead of that loop ?
This loop also contains path_get_longterm() and we need to do it before dropping fs->lock. We are holding a reference to new_root, all right, but once it's place into ->fs->{root,pwd} of another task and ->fs->lock is dropped, there's nothing to stop that task of doing chdir() and dropping its reference. Which could outweight the single reference we are holding pretty soon...
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