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author | Paolo Bonzini <pbonzini@redhat.com> | 2014-11-07 23:04:00 +0100 |
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committer | Jens Axboe <axboe@fb.com> | 2014-11-11 19:04:49 +0100 |
commit | 2a90d4aae5509e9cf1ba848c5d0b3458201160a0 (patch) | |
tree | f327e5db3649df99d7f957ff6932eb7e7b5fc4ed /kernel/pid.c | |
parent | blk_mq: call preempt_disable/enable in blk_mq_run_hw_queue, and only if needed (diff) | |
download | linux-2a90d4aae5509e9cf1ba848c5d0b3458201160a0.tar.xz linux-2a90d4aae5509e9cf1ba848c5d0b3458201160a0.zip |
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 <axboe@kernel.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Clark Williams <williams@redhat.com>
Tested-by: Clark Williams <williams@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'kernel/pid.c')
0 files changed, 0 insertions, 0 deletions