From: Paolo Bonzini Date: Fri, 7 Nov 2014 22:04:00 +0000 (+0100) Subject: blk-mq: use get_cpu/put_cpu instead of preempt_disable/preempt_enable X-Git-Tag: omap-for-v3.19/fixes-rc1~95^2~19 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2a90d4aae5509e9cf1ba848c5d0b3458201160a0;p=pandora-kernel.git blk-mq: use get_cpu/put_cpu instead of preempt_disable/preempt_enable blk-mq is using preempt_disable/enable in order to ensure that the queue runners are placed on the right CPU. This does not work with the RT patches, because __blk_mq_run_hw_queue takes a non-raw spinlock with the preemption-disabled region. If there is contention on the lock, this violates the rules for preemption-disabled regions. While this should be easily fixable within the RT patches just by doing migrate_disable/enable, we can do better and document _why_ this particular region runs with disabled preemption. After the previous patch, it is trivial to switch it to get/put_cpu; the RT patches then can change it to get_cpu_light, which lets virtio-blk run under RT kernels. Cc: Jens Axboe Cc: Thomas Gleixner Reported-by: Clark Williams Tested-by: Clark Williams Signed-off-by: Paolo Bonzini Signed-off-by: Jens Axboe --- Reading git-diff-tree failed