Messages in this thread | | | Date | Wed, 5 Sep 2007 09:05:47 -0700 | From | Andrew Morton <> | Subject | Re: Race in the inotify debug code |
| |
> On Thu, 23 Aug 2007 11:25:18 -0400 Chuck Ebbert <cebbert@redhat.com> wrote: > https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=248355 > > Description of problem: > Warnings in the kernel log (dmesg): > BUG: warning at fs/inotify.c:172/set_dentry_child_flags() (Not tainted) > [<c0497a37>] set_dentry_child_flags+0x67/0x13d > [<c0497c27>] remove_watch_no_event+0x2f/0x3b > [<c0497d15>] inotify_remove_watch_locked+0x12/0x3e > [<c0600c17>] mutex_lock+0x1a/0x29 > [<c0497fdd>] inotify_rm_wd+0x6d/0x8a > [<c04983b1>] sys_inotify_rm_watch+0x38/0x4f > [<c0404f70>] syscall_call+0x7/0xb > > Appears randomly, about every second/third day. > > Still happening in kernel 2.6.22. > > > static void set_dentry_child_flags(struct inode *inode, int watched) > ... > spin_lock(&dcache_lock); > list_for_each_entry(alias, &inode->i_dentry, d_alias) { > struct dentry *child; > > list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) { > if (!child->d_inode) { > WARN_ON(child->d_flags & DCACHE_INOTIFY_PARENT_WATCHED); > continue; > } > > But in dcache.c, the locks are dropped before this flag is cleared, leaving > a race window: > > void d_delete(struct dentry * dentry) > ... > spin_lock(&dcache_lock); > spin_lock(&dentry->d_lock); > isdir = S_ISDIR(dentry->d_inode->i_mode); > if (atomic_read(&dentry->d_count) == 1) { > dentry_iput(dentry); <================ drops dcache_lock and dentry->d_lock > fsnotify_nameremove(dentry, isdir); > > /* remove this and other inotify debug checks after 2.6.18 */ > dentry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED; > return; > } > > (The comment is nice, it says the debug code should have been removed long ago.)
We've been chasing this bug for a year or so. Thanks for maybe-solving it. I forwarded your email to Nick a few days ago but he's presently tied up with kernel slummit. Please let us not forget about this? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |