tipc: introduce new spinlock to protect struct link_req
Currently, only 'bearer_lock' is used to protect struct link_req in
the function disc_timeout(). This is unsafe, since the member fields
'num_nodes' and 'timer_intv' might be accessed by below three different
threads simultaneously, none of them grabbing bearer_lock in the
critical region:
link_activate()
tipc_bearer_add_dest()
tipc_disc_add_dest()
req->num_nodes++;
tipc_link_reset()
tipc_bearer_remove_dest()
tipc_disc_remove_dest()
req->num_nodes--
disc_update()
read req->num_nodes
write req->timer_intv
disc_timeout()
read req->num_nodes
read/write req->timer_intv
Without lock protection, the only symptom of a race is that discovery
messages occasionally may not be sent out. This is not fatal, since such
messages are best-effort anyway. On the other hand, since discovery
messages are not time critical, adding a protecting lock brings no
serious overhead either. So we add a new, dedicated spinlock in
order to guarantee absolute data consistency in link_req objects.
This also helps reduce the overall role of the bearer_lock, which
we want to remove completely in a later commit series.
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed