tipc: involve reference counter for subscriber
At present subscriber's lock is used to protect the subscription list of subscriber as well as subscriptions linked into the list. While one or all subscriptions are deleted through iterating the list, the subscriber's lock must be held. Meanwhile, as deletion of subscription may happen in subscription timer's handler, the lock must be grabbed in the function as well. When subscription's timer is terminated with del_timer_sync() during above iteration, subscriber's lock has to be temporarily released, otherwise, deadlock may occur. However, the temporary release may cause the double free of a subscription as the subscription is not disconnected from the subscription list. Now if a reference counter is introduced to subscriber, subscription's timer can be asynchronously stopped with del_timer(). As a result, the issue is not only able to be fixed, but also relevant code is pretty readable and understandable. Signed-off-by: NYing Xue <ying.xue@windriver.com> Reviewed-by: NJon Maloy <jon.maloy@ericson.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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