2 locks are executed in 2 places in opposite orders.
Consider the following scenario, threads A and B:
(A)
* fdset_event_dispatch() start
* pfdentry->busy = 1; (lock #1)
* vhost_user_read_cb() start
* vhost_destroy_device() start
(B)
* rte_vhost_driver_unregister() start
* pthread_mutex_lock(&vsocket->conn_mutex); (lock #2)
* fdset_del()
* endless loop, waiting for pfdentry->busy == 0 (lock #1)
(A)
* vhost_destroy_device() end
* pthread_mutex_lock(&vsocket->conn_mutex); (lock #2)
(mutex already locked - deadlock at this point)
Thread B has locked vsocket->conn_mutex and is in while(1)
loop waiting for given fd to change it's busy flag to 0.
Thread A would have to finish vhost_user_read_cb() in order
to set busy flag back to 0, but that can't happen due to
the vsocket->conn_mutex lock.
This patch defers the fdset_del(), so that it's called outside of
vsocket->conn_mutex.
Change-Id: Ifb5d4699bdafe96a573444c11ad4eae3adc359f5
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/375910
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Pawel Wodkowski <pawelx.wodkowski@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
1eac307937