Messages in this thread | | | Subject | Re: [RFC/PATCH] No get_user/put_user while holding mmap_sem in do_pages_stat? | From | Peter Zijlstra <> | Date | Tue, 09 Dec 2008 17:35:46 +0100 |
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On Sun, 2008-12-07 at 15:21 +0100, Brice Goglin wrote: > Andrew Morton wrote: > > Was lockdep able to tell you about this in any way? > > > > With CONFIG_PROVE_LOCKING (assuming that it's enough), it doesn't detect > the problem for real. It just says "possible recursive locking detected" > between do_page_fault and sys_move_pages.
That is real - how much more real do you need a description of a recursive deadlock to be?
> I actually understood the > problem after hitting sysrq-t and always getting the following backtraces: > * thread 1 > [<ffffffff80430cb8>] __down_write_nested+0x9c/0xb4 > [<ffffffff8028c2c4>] sys_mprotect+0xcc/0x230 > * thread 2 > [<ffffffff80430d73>] __down_read+0x9c/0xb4 > [<ffffffff80223f5c>] do_page_fault+0x551/0x9d9 > [...] > [<ffffffff8043111a>] error_exit+0x0/0x70 > [<ffffffff802f5bec>] cap_task_movememory+0x0/0x3 > [<ffffffff8032b99d>] __put_user_4+0x1d/0x30 > [<ffffffff802a091f>] sys_move_pages+0x453/0x4c0
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