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Subject[PATCH v1 0/2] blk-mq: fix oops caused by CPU hotplug
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Hi Guys,

Dongsu Park reported[1] that kernel oops can be triggered easily by
CPU plug when there is pending I/O on virtio-scsi.

Turns out two problems exist in blk-mq core code and both can trigger
oops by CPU plug:
- timeout handling vs CPU hotplug, especially unmapped hw queue tags
is still touched by timeout handler
- in case of shared tags, there is one bug about setting and checking
hctx->tags during CPU hotplug

The two patches fix the two problem, and Dongsu has verified that
the oops is fixed with the two patches too.

[1], http://marc.info/?t=142926389200008&r=1&w=2

V1:
- update comment
- moving tags allocation in blk_mq_map_swqueue() because
unmapped hw queue can be remapped after CPU topo is changed

block/blk-mq.c | 50 ++++++++++++++++++++++++++------------------------
1 file changed, 26 insertions(+), 24 deletions(-)


Thanks,
Ming Lei



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