Stefan Hajnoczi be2c42b97c virtio-scsi: reset SCSI devices from main loop thread ... When an IOThread is configured, the ctrl virtqueue is processed in the IOThread. TMFs that reset SCSI devices are currently called directly from the IOThread and trigger an assertion failure in blk_drain() from the following call stack: virtio_scsi_handle_ctrl_req -> virtio_scsi_do_tmf -> device_code_reset -> scsi_disk_reset -> scsi_device_purge_requests -> blk_drain ../block/block-backend.c:1780: void blk_drain(BlockBackend *): Assertion `qemu_in_main_thread()' failed. The blk_drain() function is not designed to be called from an IOThread because it needs the Big QEMU Lock (BQL). This patch defers TMFs that reset SCSI devices to a Bottom Half (BH) that runs in the main loop thread under the BQL. This way it's safe to call blk_drain() and the assertion failure is avoided. Introduce s->tmf_bh_list for tracking TMF requests that have been deferred to the BH. When the BH runs it will grab the entire list and process all requests. Care must be taken to clear the list when the virtio-scsi device is reset or unrealized. Otherwise deferred TMF requests could execute later and lead to use-after-free or other undefined behavior. The s->resetting counter that's used by TMFs that reset SCSI devices is accessed from multiple threads. This patch makes that explicit by using atomic accessor functions. With this patch applied the counter is only modified by the main loop thread under the BQL but can be read by any thread. Reported-by: Qing Wang <qinwang@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20230221212218.1378734-4-stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>		2023-02-23 19:49:35 +01:00
..
emulation.c
esp-pci.c
esp.c
Kconfig
lsi53c895a.c
megasas.c
meson.build
mfi.h
mpi.h
mptconfig.c
mptendian.c
mptsas.c
mptsas.h
scsi-bus.c
scsi-disk.c
scsi-generic.c
spapr_vscsi.c
srp.h
trace-events
trace.h
vhost-scsi-common.c
vhost-scsi.c
vhost-user-scsi.c
viosrp.h
virtio-scsi-dataplane.c
virtio-scsi.c	virtio-scsi: reset SCSI devices from main loop thread	2023-02-23 19:49:35 +01:00
vmw_pvscsi.c
vmw_pvscsi.h