tipc: introduce new spinlock to protect struct link_req (f9a2c80b) · Commits · 戴 / test

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>

net/tipc/discover.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -50,6 +50,7 @@
		* @dest: destination address for request messages
		* @domain: network domain to which links can be established
		* @num_nodes: number of nodes currently discovered (i.e. with an active link)
		* @lock: spinlock for controlling access to requests
		* @buf: request message to be (repeatedly) sent
		* @timer: timer governing period between requests
		* @timer_intv: current interval between requests (in ms)
		@@ -59,6 +60,7 @@ struct tipc_link_req {
		struct tipc_media_addr dest;
		u32 domain;
		int num_nodes;
		spinlock_t lock;
		struct sk_buff *buf;
		struct timer_list timer;
		unsigned int timer_intv;
		@@ -274,7 +276,9 @@ static void disc_update(struct tipc_link_req *req)
		*/
		void tipc_disc_add_dest(struct tipc_link_req *req)
		{
		spin_lock_bh(&req->lock);
		req->num_nodes++;
		spin_unlock_bh(&req->lock);
		}

		/**
		@@ -283,8 +287,10 @@ void tipc_disc_add_dest(struct tipc_link_req *req)
		*/
		void tipc_disc_remove_dest(struct tipc_link_req *req)
		{
		spin_lock_bh(&req->lock);
		req->num_nodes--;
		disc_update(req);
		spin_unlock_bh(&req->lock);
		}

		/**
		@@ -297,7 +303,7 @@ static void disc_timeout(struct tipc_link_req *req)
		{
		int max_delay;

		spin_lock_bh(&req->bearer->lock);
		spin_lock_bh(&req->lock);

		/* Stop searching if only desired node has been found */
		if (tipc_node(req->domain) && req->num_nodes) {
		@@ -325,7 +331,7 @@ static void disc_timeout(struct tipc_link_req *req)

		k_start_timer(&req->timer, req->timer_intv);
		exit:
		spin_unlock_bh(&req->bearer->lock);
		spin_unlock_bh(&req->lock);
		}

		/**
		@@ -356,6 +362,7 @@ int tipc_disc_create(struct tipc_bearer b_ptr, struct tipc_media_addr dest,
		req->domain = dest_domain;
		req->num_nodes = 0;
		req->timer_intv = TIPC_LINK_REQ_INIT;
		spin_lock_init(&req->lock);
		k_init_timer(&req->timer, (Handler)disc_timeout, (unsigned long)req);
		k_start_timer(&req->timer, req->timer_intv);
		b_ptr->link_req = req;

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