There is currently a small window after we stop
session's pollers and before we mark the session
as stopped (by setting vsession->lcore to -1). If
spdk_vhost_dev_foreach_session() is called within
this window, its callback could assume the session
is still running and for example in vhost scsi
target hotremove case, could destroy an io_channel
for the second time - as it'd first done when the
session was stopped. That's a bug.
A similar case exists for session start.
We fix the above by setting vsession->lcore directly
after starting or stopping the session, hence
eliminating the possible window for data races.
This has a few implications:
* spdk_vhost_session_send_event() called before
session start can't operate on vsession->lcore,
so it needs to be provided with the lcore as
an additional parameter now.
* the vsession->lcore can't be accessed until
spdk_vhost_session_start_done() is called, so
its existing usages were replaced with
spdk_env_get_current_core()
* active_session_num is decremented right after
spdk_vhost_session_stop_done() is called and
before spdk_vhost_session_send_event() returns,
so some active_session_num == 1 checks meaning
"the last session gets stopped now" needed to be
changed to check against == 0, as if "the last
session has been just stopped"
Change-Id: I5781bb0ce247425130c9672e0df27d06b6234317
Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/448229
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
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