[PATCH 2/2] net/sock: Propagate WF_SYNC only when requested

Use SOCK_SYNC_WAKEUP to select between synchronous and asynchronous wakeup
wakeup APIs. This avoids propagating WF_SYNC when no blocking waiter is
expected. All wakeup locations in networking code that currently issue
synchronous poll-style wakeups unconditionally are updated.

Signed-off-by: Srikar Dronamraju <[email protected]>
---
 net/core/sock.c    | 31 ++++++++++++++++++++++++-------
 net/sctp/socket.c  | 10 ++++++++--
 net/smc/af_smc.c   |  4 ++--
 net/smc/smc_rx.c   | 10 ++++++++--
 net/tipc/socket.c  | 22 +++++++++++++++++-----
 net/unix/af_unix.c | 26 ++++++++++++++++++--------
 6 files changed, 77 insertions(+), 26 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 8a59bfaa8096..a214e883b14b 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3652,9 +3652,15 @@ void sock_def_readable(struct sock *sk)
 
 	rcu_read_lock();
 	wq = rcu_dereference(sk->sk_wq);
-	if (skwq_has_sleeper(wq))
-		wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN | EPOLLPRI |
+	if (skwq_has_sleeper(wq)) {
+		if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+			wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN | EPOLLPRI |
+						EPOLLRDNORM | EPOLLRDBAND);
+		} else {
+			wake_up_interruptible_poll(&wq->wait, EPOLLIN | EPOLLPRI |
 						EPOLLRDNORM | EPOLLRDBAND);
+		}
+	}
 	sk_wake_async_rcu(sk, SOCK_WAKE_WAITD, POLL_IN);
 	rcu_read_unlock();
 }
@@ -3670,9 +3676,15 @@ static void sock_def_write_space(struct sock *sk)
 	 */
 	if (sock_writeable(sk)) {
 		wq = rcu_dereference(sk->sk_wq);
-		if (skwq_has_sleeper(wq))
-			wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
+		if (skwq_has_sleeper(wq)) {
+			if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+				wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
+						EPOLLWRNORM | EPOLLWRBAND);
+			} else {
+				wake_up_interruptible_poll(&wq->wait, EPOLLOUT |
 						EPOLLWRNORM | EPOLLWRBAND);
+			}
+		}
 
 		/* Should agree with poll, otherwise some programs break */
 		sk_wake_async_rcu(sk, SOCK_WAKE_SPACE, POLL_OUT);
@@ -3695,10 +3707,15 @@ static void sock_def_write_space_wfree(struct sock *sk, int wmem_alloc)
 
 		/* rely on refcount_sub from sock_wfree() */
 		smp_mb__after_atomic();
-		if (wq && waitqueue_active(&wq->wait))
-			wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
+		if (wq && waitqueue_active(&wq->wait)) {
+			if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+				wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
 						EPOLLWRNORM | EPOLLWRBAND);
-
+			} else {
+				wake_up_interruptible_poll(&wq->wait, EPOLLOUT |
+						EPOLLWRNORM | EPOLLWRBAND);
+			}
+		}
 		/* Should agree with poll, otherwise some programs break */
 		sk_wake_async_rcu(sk, SOCK_WAKE_SPACE, POLL_OUT);
 	}
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index c7b9e325ec1c..9cb3432f065a 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9348,9 +9348,15 @@ void sctp_data_ready(struct sock *sk)
 
 	rcu_read_lock();
 	wq = rcu_dereference(sk->sk_wq);
-	if (skwq_has_sleeper(wq))
-		wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN |
+	if (skwq_has_sleeper(wq)) {
+		if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+			wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN |
+					EPOLLRDNORM | EPOLLRDBAND);
+		} else {
+			wake_up_interruptible_poll(&wq->wait, EPOLLIN |
 						EPOLLRDNORM | EPOLLRDBAND);
+		}
+	}
 	sk_wake_async_rcu(sk, SOCK_WAKE_WAITD, POLL_IN);
 	rcu_read_unlock();
 }
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index b5db69073e20..1a6ea2e30769 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -819,10 +819,10 @@ static void smc_fback_wakeup_waitqueue(struct smc_sock *smc, void *key)
 		wake_up_interruptible_all(&wq->wait);
 	} else {
 		flags = key_to_poll(key);
-		if (flags & (EPOLLIN | EPOLLOUT))
+		if (flags & (EPOLLIN | EPOLLOUT) && sock_flag(&smc->sk, SOCK_SYNC_WAKEUP))
 			/* sk_data_ready or sk_write_space */
 			wake_up_interruptible_sync_poll(&wq->wait, flags);
-		else if (flags & EPOLLERR)
+		else
 			/* sk_error_report */
 			wake_up_interruptible_poll(&wq->wait, flags);
 	}
diff --git a/net/smc/smc_rx.c b/net/smc/smc_rx.c
index c1d9b923938d..4e288a2364d2 100644
--- a/net/smc/smc_rx.c
+++ b/net/smc/smc_rx.c
@@ -39,9 +39,15 @@ static void smc_rx_wake_up(struct sock *sk)
 	/* called already in smc_listen_work() */
 	rcu_read_lock();
 	wq = rcu_dereference(sk->sk_wq);
-	if (skwq_has_sleeper(wq))
-		wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN | EPOLLPRI |
+	if (skwq_has_sleeper(wq)) {
+		if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+			wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN | EPOLLPRI |
 						EPOLLRDNORM | EPOLLRDBAND);
+		} else {
+			wake_up_interruptible_poll(&wq->wait, EPOLLIN | EPOLLPRI |
+						EPOLLRDNORM | EPOLLRDBAND);
+		}
+	}
 	sk_wake_async_rcu(sk, SOCK_WAKE_WAITD, POLL_IN);
 	if ((sk->sk_shutdown == SHUTDOWN_MASK) ||
 	    (sk->sk_state == SMC_CLOSED))
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index e564341e0216..9fa83a89882c 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -2116,9 +2116,15 @@ static void tipc_write_space(struct sock *sk)
 
 	rcu_read_lock();
 	wq = rcu_dereference(sk->sk_wq);
-	if (skwq_has_sleeper(wq))
-		wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
+	if (skwq_has_sleeper(wq)) {
+		if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+			wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
 						EPOLLWRNORM | EPOLLWRBAND);
+		} else {
+			wake_up_interruptible_poll(&wq->wait, EPOLLOUT |
+						EPOLLWRNORM | EPOLLWRBAND);
+		}
+	}
 	rcu_read_unlock();
 }
 
@@ -2134,9 +2140,15 @@ static void tipc_data_ready(struct sock *sk)
 
 	rcu_read_lock();
 	wq = rcu_dereference(sk->sk_wq);
-	if (skwq_has_sleeper(wq))
-		wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN |
-						EPOLLRDNORM | EPOLLRDBAND);
+	if (skwq_has_sleeper(wq)) {
+		if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+			wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN |
+							EPOLLRDNORM | EPOLLRDBAND);
+		} else {
+			wake_up_interruptible_poll(&wq->wait, EPOLLIN |
+							EPOLLRDNORM | EPOLLRDBAND);
+		}
+	}
 	rcu_read_unlock();
 }
 
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f7a9d55eee8a..15ebcc2d9d58 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -601,9 +601,15 @@ static void unix_write_space(struct sock *sk)
 	rcu_read_lock();
 	if (unix_writable(sk, READ_ONCE(sk->sk_state))) {
 		wq = rcu_dereference(sk->sk_wq);
-		if (skwq_has_sleeper(wq))
-			wake_up_interruptible_sync_poll(&wq->wait,
-				EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
+		if (skwq_has_sleeper(wq)) {
+			if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+				wake_up_interruptible_sync_poll(&wq->wait,
+					EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
+			} else {
+				wake_up_interruptible_poll(&wq->wait,
+					EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
+			}
+		}
 		sk_wake_async_rcu(sk, SOCK_WAKE_SPACE, POLL_OUT);
 	}
 	rcu_read_unlock();
@@ -2603,11 +2609,15 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
 		goto out;
 	}
 
-	if (wq_has_sleeper(&u->peer_wait))
-		wake_up_interruptible_sync_poll(&u->peer_wait,
-						EPOLLOUT | EPOLLWRNORM |
-						EPOLLWRBAND);
-
+	if (wq_has_sleeper(&u->peer_wait)) {
+		if (sock_flag(sk, SOCK_SYNC_WAKEUP)) {
+			wake_up_interruptible_sync_poll(&u->peer_wait,
+						EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
+		} else {
+			wake_up_interruptible_poll(&u->peer_wait,
+						EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
+		}
+	}
 	if (msg->msg_name) {
 		unix_copy_addr(msg, skb->sk);
 
-- 
2.52.0