Messages in this thread | | | Date | Tue, 20 Apr 2004 13:34:29 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] i2o_block Fix, possible CFQ elevator problem? |
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On Tue, Apr 20 2004, Warren Togami wrote: > Jens Axboe wrote: > >>> > >>>Repeat the tests that made it crash. The last patch I sent should work > >>>for you, at least until the real issue is found. > >>> > >> > >>Tested your patch, it indeed does seem to keep the system stable. If I > >>am understanding it right, the patch disables merging in the case where > >>it would have caused a BUG condition? (Less efficiency.) > > > > > > Bad news... much later during the test the system locked up. During > this test we did not use "sync" but just let all four bonnie++'s run. > > http://togami.com/~warren/archive/2004/i2o_cfq_quad_bonnie3.txt > ----------- [cut here ] --------- [please bite here ] --------- > Kernel BUG at cfq_iosched:404 > invalid operand: 0000 [1] SMP
Sorry about that, that's actually expected when we know this bug exists. You need to move the cfq_remove_merge_hints(q, crq) before the BUG_ON(q->last_merge == rq) check, or (better) just remove it completely. There's no way that q->last_merge could be set to this request after cfq_remove_merge_hints() was called.
-- Jens Axboe
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