sctp: not disable bh in the whole sctp_get_port_local() (3106ecb4) · Commits · 戴 / test

With disabling bh in the whole sctp_get_port_local(), when snum == 0 and too many ports have been used, the do-while loop will take the cpu for a long time and cause cpu stuck: [ ] watchdog: BUG: soft lockup - CPU#11 stuck for 22s! [ ] RIP: 0010:native_queued_spin_lock_slowpath+0x4de/0x940 [ ] Call Trace: [ ] _raw_spin_lock+0xc1/0xd0 [ ] sctp_get_port_local+0x527/0x650 [sctp] [ ] sctp_do_bind+0x208/0x5e0 [sctp] [ ] sctp_autobind+0x165/0x1e0 [sctp] [ ] sctp_connect_new_asoc+0x355/0x480 [sctp] [ ] __sctp_connect+0x360/0xb10 [sctp] There's no need to disable bh in the whole function of sctp_get_port_local. So fix this cpu stuck by removing local_bh_disable() called at the beginning, and using spin_lock_bh() instead. The same thing was actually done for inet_csk_get_port() in Commit ("tcp/dccp: better use of ephemeral ports in bind()"). Thanks to Marcelo for pointing the buggy code out. v1->v2: - use cond_resched() to yield cpu to other tasks if needed, as Eric noticed. Fixes: ("Linux-2.6.12-rc2") Reported-by:

Ying Xu <yinxu@redhat.com> Signed-off-by:

Xin Long <lucien.xin@gmail.com> Acked-by:

Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/sctp/socket.c

+6 −10

Original line number	Diff line number	Diff line
		@@ -8060,8 +8060,6 @@ static int sctp_get_port_local(struct sock sk, union sctp_addr addr)

		pr_debug("%s: begins, snum:%d\n", __func__, snum);

		local_bh_disable();

		if (snum == 0) {
		/* Search for an available port. */
		int low, high, remaining, index;
		@@ -8079,20 +8077,21 @@ static int sctp_get_port_local(struct sock sk, union sctp_addr addr)
		continue;
		index = sctp_phashfn(net, rover);
		head = &sctp_port_hashtable[index];
		spin_lock(&head->lock);
		spin_lock_bh(&head->lock);
		sctp_for_each_hentry(pp, &head->chain)
		if ((pp->port == rover) &&
		net_eq(net, pp->net))
		goto next;
		break;
		next:
		spin_unlock(&head->lock);
		spin_unlock_bh(&head->lock);
		cond_resched();
		} while (--remaining > 0);

		/* Exhausted local port range during search? */
		ret = 1;
		if (remaining <= 0)
		goto fail;
		return ret;

		/* OK, here is the one we will use. HEAD (the port
		* hash table list entry) is non-NULL and we hold it's
		@@ -8107,7 +8106,7 @@ static int sctp_get_port_local(struct sock sk, union sctp_addr addr)
		* port iterator, pp being NULL.
		*/
		head = &sctp_port_hashtable[sctp_phashfn(net, snum)];
		spin_lock(&head->lock);
		spin_lock_bh(&head->lock);
		sctp_for_each_hentry(pp, &head->chain) {
		if ((pp->port == snum) && net_eq(pp->net, net))
		goto pp_found;
		@@ -8207,10 +8206,7 @@ success:
		ret = 0;

		fail_unlock:
		spin_unlock(&head->lock);

		fail:
		local_bh_enable();
		spin_unlock_bh(&head->lock);
		return ret;
		}

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