4.19-stable review patch. If anyone has any objections, please let me know.
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From: Tung Nguyen tung.q.nguyen@dektech.com.au
[ Upstream commit bfd07f3dd4f111b884d7922b37eb239280f83d8c ]
When sending multicast messages via blocking socket, if sending link is congested (tsk->cong_link_cnt is set to 1), the sending thread will be put into sleeping state. However, tipc_sk_filter_rcv() is called under socket spin lock but tipc_wait_for_cond() is not. So, there is no guarantee that the setting of tsk->cong_link_cnt to 0 in tipc_sk_proto_rcv() in CPU-1 will be perceived by CPU-0. If that is the case, the sending thread in CPU-0 after being waken up, will continue to see tsk->cong_link_cnt as 1 and put the sending thread into sleeping state again. The sending thread will sleep forever.
CPU-0 | CPU-1 tipc_wait_for_cond() | { | // condition_ = !tsk->cong_link_cnt | while ((rc_ = !(condition_))) { | ... | release_sock(sk_); | wait_woken(); | | if (!sock_owned_by_user(sk)) | tipc_sk_filter_rcv() | { | ... | tipc_sk_proto_rcv() | { | ... | tsk->cong_link_cnt--; | ... | sk->sk_write_space(sk); | ... | } | ... | } sched_annotate_sleep(); | lock_sock(sk_); | remove_wait_queue(); | } | } |
This commit fixes it by adding memory barrier to tipc_sk_proto_rcv() and tipc_wait_for_cond().
Acked-by: Jon Maloy jon.maloy@ericsson.com Signed-off-by: Tung Nguyen tung.q.nguyen@dektech.com.au Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/tipc/socket.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/net/tipc/socket.c +++ b/net/tipc/socket.c @@ -377,11 +377,13 @@ static int tipc_sk_sock_err(struct socke
#define tipc_wait_for_cond(sock_, timeo_, condition_) \ ({ \ + DEFINE_WAIT_FUNC(wait_, woken_wake_function); \ struct sock *sk_; \ int rc_; \ \ while ((rc_ = !(condition_))) { \ - DEFINE_WAIT_FUNC(wait_, woken_wake_function); \ + /* coupled with smp_wmb() in tipc_sk_proto_rcv() */ \ + smp_rmb(); \ sk_ = (sock_)->sk; \ rc_ = tipc_sk_sock_err((sock_), timeo_); \ if (rc_) \ @@ -1961,6 +1963,8 @@ static void tipc_sk_proto_rcv(struct soc return; case SOCK_WAKEUP: tipc_dest_del(&tsk->cong_links, msg_orignode(hdr), 0); + /* coupled with smp_rmb() in tipc_wait_for_cond() */ + smp_wmb(); tsk->cong_link_cnt--; wakeup = true; break;