Messages in this thread | | | Date | Wed, 17 Jul 2013 14:14:53 -0600 | From | Jens Axboe <> | Subject | Re: [PATCH RFC] lib: Make radix_tree_node_alloc() irq safe |
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On Tue, Jul 16 2013, Jan Kara wrote: > With users of radix_tree_preload() run from interrupt (CFQ is one such > possible user), the following race can happen: > > radix_tree_preload() > ... > radix_tree_insert() > radix_tree_node_alloc() > if (rtp->nr) { > ret = rtp->nodes[rtp->nr - 1]; > <interrupt> > ... > radix_tree_preload() > ... > radix_tree_insert() > radix_tree_node_alloc() > if (rtp->nr) { > ret = rtp->nodes[rtp->nr - 1]; > > And we give out one radix tree node twice. That clearly results in radix > tree corruption with different results (usually OOPS) depending on which > two users of radix tree race. > > Fix the problem by disabling interrupts when working with rtp variable. > In-interrupt user can still deplete our preloaded nodes but at least we > won't corrupt radix trees.
Looks good to me, great catch Jan.
-- Jens Axboe
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