Use thr_once() with once_t controls to initialize various thread_key_t

objects used to provide per-thread storage in the RPC code.  Almost all
of these used double-checking with a dedicated mutex (tsd_lock) to do this
before.  However, that is not always safe with more relaxed memory orders.
There were also other bugs, such as one in __rpc_createrr() that caused a
new key to be allocated each time __rpc_createrr() was invoked.

PR:		threads/144558
Reported by:	Sam Robb  samrobb of averesystems com (key leak)
MFC after:	1 week

1 files changed, 9 insertions, 6 deletions

diff --git a/lib/libc/rpc/rpc_soc.c b/lib/libc/rpc/rpc_soc.c
index 5922063..2568d43 100644
--- a/lib/libc/rpc/rpc_soc.c
+++ b/lib/libc/rpc/rpc_soc.c
@@ -360,6 +360,14 @@ registerrpc(prognum, versnum, procnum, progname, inproc, outproc)
  */
 static thread_key_t	clnt_broadcast_key;
 static resultproc_t	clnt_broadcast_result_main;
+static once_t		clnt_broadcast_once = ONCE_INITIALIZER;
+
+static void
+clnt_broadcast_key_init(void)
+{
+
+	thr_keycreate(&clnt_broadcast_key, free);
+}
 
 /*
  * Need to translate the netbuf address into sockaddr_in address.
@@ -402,12 +410,7 @@ clnt_broadcast(prog, vers, proc, xargs, argsp, xresults, resultsp, eachresult)
 	if (thr_main())
 		clnt_broadcast_result_main = eachresult;
 	else {
-		if (clnt_broadcast_key == 0) {
-			mutex_lock(&tsd_lock);
-			if (clnt_broadcast_key == 0)
-				thr_keycreate(&clnt_broadcast_key, free);
-			mutex_unlock(&tsd_lock);
-		}
+		thr_once(&clnt_broadcast_once, clnt_broadcast_key_init);
 		thr_setspecific(clnt_broadcast_key, (void *) eachresult);
 	}
 	return rpc_broadcast((rpcprog_t)prog, (rpcvers_t)vers,