Messages in this thread | | | Date | Mon, 24 Aug 2009 11:06:24 +0200 | Subject | Re: kernel bugs 2.6.31-rc6 | From | Zdenek Kabelac <> |
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2009/8/16 Eric Paris <eparis@redhat.com>: > On Sat, 2009-08-15 at 10:52 -0700, Linus Torvalds wrote: >> >> On Sat, 15 Aug 2009, Linus Torvalds wrote: >> > >> > For example, fsnotify_remove_priv_from_event() will remove the private >> > data event from the list, but what if there are _multiple_ entries with >> > the same 'group' entry? If so, it will remove just the first one. > > I can happen, but ONLY for the staticly declared q_overflow_event in > notification.c. If the refcnt on that ever hits 0 to trigger this bug > we are in some serious dodo. > >> Hmm. Looking closer, that shouldn't much matter. Each time we added an >> entry in private_data_list, we would have done a >> 'fsnotify_get_event(event)' due to adding it to the 'golder->event_list'. >> >> That said, there does seem to be some dubious code there. For example, >> in 'inotify_ignored_and_remove_idr()', we do this: >> >> fsnotify_add_notify_event(group, ignored_event, fsn_event_priv); >> >> /* did the private data get added? */ >> if (list_empty(&fsn_event_priv->event_list)) >> inotify_free_event_priv(fsn_event_priv); > >> and we do it without holding any locks at all. So as far as I can tell, >> what could happen is that 'fsnotify_add_notify_event()' actually adds the >> private event (fsn_event_priv), but then before we check that the >> event_list is empty, another user (on another CPU, or preempted on the >> same CPU - Christoph has both PREEMPT and SMP on) comes along, picks up >> the private event and frees it (and re-uses it). > > Actually you look correct in your assessment that there is a race here. > I guess I could imagine a way to make it panic like this, but I would > have expected a different problem in that after I freed this memory > (which wasn't mine any more) the other task which owned this memory > would have to still be able to run list_for_each_entry, but find that > it's group was no longer there. Not sure how could screw up the group, > but not the list entries. > > I'll fix this race tonight or in the morning. > > I'm downloading and installing KDE, as I guess kde uses inotify pretty > hard since both Mikko and Christoph were using kde.
Hi
I'm not sure how it is related - but I've got folllowing ooops while running yum upgrade I'm using gnome.
I've added the backtrace to the Bugzilla mentioned in this thread.
http://bugzilla.kernel.org/show_bug.cgi?id=13729#c7
Zdenek -- 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/
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