From 512137eeff00f73a8a62e481a6575f1556cf962c Mon Sep 17 00:00:00 2001 From: Erik Hugne Date: Fri, 6 Dec 2013 10:08:00 -0500 Subject: tipc: remove interface state mirroring in bearer struct 'tipc_bearer' is a generic representation of the underlying media type, and exists in a one-to-one relationship to each interface TIPC is using. The struct contains a 'blocked' flag that mirrors the operational and execution state of the represented interface, and is updated through notification calls from the latter. The users of tipc_bearer are checking this flag before each attempt to send a packet via the interface. This state mirroring serves no purpose in the current code base. TIPC links will not discover a media failure any faster through this mechanism, and in reality the flag only adds overhead at packet sending and reception. Furthermore, the fact that the flag needs to be protected by a spinlock aggregated into tipc_bearer has turned out to cause a serious and completely unnecessary deadlock problem. CPU0 CPU1 ---- ---- Time 0: bearer_disable() link_timeout() Time 1: spin_lock_bh(&b_ptr->lock) tipc_link_push_queue() Time 2: tipc_link_delete() tipc_bearer_blocked(b_ptr) Time 3: k_cancel_timer(&req->timer) spin_lock_bh(&b_ptr->lock) Time 4: del_timer_sync(&req->timer) I.e., del_timer_sync() on CPU0 never returns, because the timer handler on CPU1 is waiting for the bearer lock. We eliminate the 'blocked' flag from struct tipc_bearer, along with all tests on this flag. This not only resolves the deadlock, but also simplifies and speeds up the data path execution of TIPC. It also fits well into our ongoing effort to make the locking policy simpler and more manageable. An effect of this change is that we can get rid of functions such as tipc_bearer_blocked(), tipc_continue() and tipc_block_bearer(). We replace the latter with a new function, tipc_reset_bearer(), which resets all links associated to the bearer immediately after an interface goes down. A user might notice one slight change in link behaviour after this change. When an interface goes down, (e.g. through a NETDEV_DOWN event) all attached links will be reset immediately, instead of leaving it to each link to detect the failure through a timer-driven mechanism. We consider this an improvement, and see no obvious risks with the new behavior. Signed-off-by: Erik Hugne Reviewed-by: Ying Xue Reviewed-by: Paul Gortmaker Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/bcast.c | 6 ------ 1 file changed, 6 deletions(-) (limited to 'net/tipc/bcast.c') diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c index 0d4402587fdf..4c2a80b3c01e 100644 --- a/net/tipc/bcast.c +++ b/net/tipc/bcast.c @@ -621,12 +621,6 @@ static int tipc_bcbearer_send(struct sk_buff *buf, struct tipc_bearer *unused1, if (!p) break; /* No more bearers to try */ - if (tipc_bearer_blocked(p)) { - if (!s || tipc_bearer_blocked(s)) - continue; /* Can't use either bearer */ - b = s; - } - tipc_nmap_diff(&bcbearer->remains, &b->nodes, &bcbearer->remains_new); if (bcbearer->remains_new.count == bcbearer->remains.count) -- cgit v1.2.3 From 581465fa285863344efc233bc546823bfabd295f Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Tue, 7 Jan 2014 17:02:44 -0500 Subject: tipc: make link start event synchronous When a link is created we delay the start event by launching it to be executed later in a tasklet. As we hold all the necessary locks at the moment of creation, and there is no risk of deadlock or contention, this delay serves no purpose in the current code. We remove this obsolete indirection step, and the associated function link_start(). At the same time, we rename the function tipc_link_stop() to the more appropriate tipc_link_purge_queues(). Signed-off-by: Jon Maloy Reviewed-by: Paul Gortmaker Signed-off-by: David S. Miller --- net/tipc/bcast.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/tipc/bcast.c') diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c index 4c2a80b3c01e..bf860d9e75af 100644 --- a/net/tipc/bcast.c +++ b/net/tipc/bcast.c @@ -794,7 +794,7 @@ void tipc_bclink_init(void) void tipc_bclink_stop(void) { spin_lock_bh(&bc_lock); - tipc_link_stop(bcl); + tipc_link_purge_queues(bcl); spin_unlock_bh(&bc_lock); memset(bclink, 0, sizeof(*bclink)); -- cgit v1.2.3