| Message ID | 20231123194931.171598-1-stefanha@redhat.com |
|---|---|
| Headers | show |
| Series | scsi: eliminate AioContext lock | expand |
On Thu, Nov 23, 2023 at 02:49:27PM -0500, Stefan Hajnoczi wrote: > The SCSI subsystem uses the AioContext lock to protect internal state. This is > necessary because the main loop and the IOThread can access SCSI state in > parallel. This inter-thread access happens during scsi_device_purge_requests() > and scsi_dma_restart_cb(). > > This patch series modifies the code so SCSI state is only accessed from the > IOThread that is executing requests. Once this has been achieved the AioContext > lock is no longer necessary. > > Note that a few aio_context_acquire()/aio_context_release() calls still remain > after this series. They surround API calls that invoke AIO_WAIT_WHILE() and > therefore still rely on the AioContext lock for now. > > Stefan Hajnoczi (4): > scsi: only access SCSIDevice->requests from one thread > virtio-scsi: don't lock AioContext around > virtio_queue_aio_attach_host_notifier() > scsi: don't lock AioContext in I/O code path > dma-helpers: don't lock AioContext in dma_blk_cb() > > include/hw/scsi/scsi.h | 7 +- > hw/scsi/scsi-bus.c | 174 ++++++++++++++++++++++---------- > hw/scsi/scsi-disk.c | 23 ----- > hw/scsi/scsi-generic.c | 20 +--- > hw/scsi/virtio-scsi-dataplane.c | 8 +- > system/dma-helpers.c | 7 +- > 6 files changed, 130 insertions(+), 109 deletions(-) CCing Kevin and qemu-block > > -- > 2.42.0 >
The SCSI subsystem uses the AioContext lock to protect internal state. This is necessary because the main loop and the IOThread can access SCSI state in parallel. This inter-thread access happens during scsi_device_purge_requests() and scsi_dma_restart_cb(). This patch series modifies the code so SCSI state is only accessed from the IOThread that is executing requests. Once this has been achieved the AioContext lock is no longer necessary. Note that a few aio_context_acquire()/aio_context_release() calls still remain after this series. They surround API calls that invoke AIO_WAIT_WHILE() and therefore still rely on the AioContext lock for now. Stefan Hajnoczi (4): scsi: only access SCSIDevice->requests from one thread virtio-scsi: don't lock AioContext around virtio_queue_aio_attach_host_notifier() scsi: don't lock AioContext in I/O code path dma-helpers: don't lock AioContext in dma_blk_cb() include/hw/scsi/scsi.h | 7 +- hw/scsi/scsi-bus.c | 174 ++++++++++++++++++++++---------- hw/scsi/scsi-disk.c | 23 ----- hw/scsi/scsi-generic.c | 20 +--- hw/scsi/virtio-scsi-dataplane.c | 8 +- system/dma-helpers.c | 7 +- 6 files changed, 130 insertions(+), 109 deletions(-)