On Thursday 06 September 2007 02:05, Andrew Morton wrote: > > On Thu, 23 Aug 2007 11:25:18 -0400 Chuck Ebbert <[EMAIL PROTECTED]> > > 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?
There is some race in the debug code, yes, but I think there could also be a real race in there too. I've posted a trial patch for it in one of the other inotify bug reports. Anyway, yes I'm inclined to just fix that and rip out the debug code. OTOH, I have been trying to get some tester to reproduce with patches and had no takers as yet... BTW, I will be away for the next few weeks so I'll be going slower than usual - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
