Messages in this thread | | | Date | Mon, 2 Feb 2009 20:56:27 +0900 | From | MinChan Kim <> | Subject | Re: [BUG??] Deadlock between kswapd and sys_inotify_add_watch(lockdep report) |
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Thanks for kind explanation. :) Unfortunately, I still have a question. :(
On Mon, Feb 02, 2009 at 12:44:45PM +0100, Peter Zijlstra wrote: > On Mon, 2009-02-02 at 20:27 +0900, MinChan Kim wrote: > > On Mon, Feb 02, 2009 at 11:40:02AM +0100, Peter Zijlstra wrote: > > > On Mon, 2009-02-02 at 19:25 +0900, MinChan Kim wrote: > > > > But, I am not sure whether it's real bug or not. > > > > > > Me neither, inode life-times are tricky, but on first sight it looks > > > real enough. > > > > > > > I always suffer from reading lockdep report's result. :( > > > > It would be better to have a document about lockdep report analysis. > > > > > > I've never found them hard to read, so I'm afraid you'll have to be more > > > explicit about what is unclear to you. > > > > It's becuase not lockdep humble report but my poor knowledge. :( > > Could you elaborate please ? > > > > >[ 331.718120] [ INFO: inconsistent lock state ] > > >[ 331.718124] 2.6.28-rc2-mm1-lockdep #6 > > >[ 331.718126] --------------------------------- > > >[ 331.718129] inconsistent {ov-reclaim-W} -> {in-reclaim-W} usage. > > ^ ^ > > write ? write ? > > Correct, we track states for read and write, for single state locks we > map everything on the exclusive state (write). > > > > > > >[ 331.718133] kswapd0/218 [HC0[0]:SC0[0]:HE0:SE1] takes: > > ^^^^^^^^^^^^^^^^^^^^^^ > > what means ? HC,SC,HE,SE > > Ah, yes, that's a bit obscure, but usually not needed. > > Hardirq Context -- irq state tracking [preempt_count tracking] > Softirq Context -- idem > > Hardirq Enabled > Softirq Enabled > > It allows you to see if the irq state tracking matches up, and what the > call context is. > > > > > > >[ 331.718136] (&inode->inotify_mutex){--..+.}, at: [<c01dba70>] inotify_inode_is_dead+0x20/0x90 > > > > > > > Is it related to recursive lock of inotify_mutex ? > > Yes. > > > but, Subject means 'inconsistent {ov-reclaim-W} -> {in-reclaim-W}', > > IOW, it's related to reclaim of GFP_FS. > > What's relation inotify_mutex and reclaim of GFP_FS? > > The lockdep report states the following: > > While holding inotify_mutex, we do a __GFP_FS allocation. > But __GFP_FS allocations can end up locking inotify_mutex. > > > I think if reclaim context which have GFP_FS already have lock A and then > > do pageout, if writepage need the lock A, we have to catch such a case. > > I thought Nick's patch's goal catchs such a case. > > Correct, it exactly does that.
But, I think such a case can be caught by lockdep of recursive detection which is existed long time ago by making you. what's difference Nick's patch and recursive lockdep ?
-- Kinds Regards MinChan Kim
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