Add a global sx sigio_lock to protect the pointer to the sigio object

of a socket.  This avoids lock order reversal caused by locking a
process in pgsigio().

sowakeup() and the callers of it (sowwakeup, soisconnected, etc.) now
require sigio_lock to be locked.  Provide sowwakeup_locked(),
soisconnected_locked(), and so on in case where we have to modify a
socket and wake up a process atomically.

1 files changed, 4 insertions, 1 deletions

diff --git a/sys/netinet/accf_data.c b/sys/netinet/accf_data.c
index b66e1c7..d38b165 100644
--- a/sys/netinet/accf_data.c
+++ b/sys/netinet/accf_data.c
@@ -56,12 +56,15 @@ static void
 sohasdata(struct socket *so, void *arg, int waitflag)
 {
 
+	SIGIO_SLOCK();
 	if (!soreadable(so)) {
+		SIGIO_SUNLOCK();
 		return;
 	}
 
 	so->so_upcall = NULL;
 	so->so_rcv.sb_flags &= ~SB_UPCALL;
-	soisconnected(so);
+	soisconnected_locked(so);
+	SIGIO_SUNLOCK();
 	return;
 }