af_unix: Annotate data-race of gc_in_progress in wait_for_unix_gc().

gc_in_progress is changed under spin_lock(&unix_gc_lock),
but wait_for_unix_gc() reads it locklessly.

Let's use READ_ONCE().

Fixes: 5f23b734 ("net: Fix soft lockups/OOM issues w/ unix garbage collector")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240123170856.41348-2-kuniyu@amazon.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/unix/garbage.c

@@ -198,7 +198,7 @@ void wait_for_unix_gc(void)
 	if (READ_ONCE(unix_tot_inflight) > UNIX_INFLIGHT_TRIGGER_GC &&
 	    !READ_ONCE(gc_in_progress))
 		unix_gc();
-	wait_event(unix_gc_wait, gc_in_progress == false);
+	wait_event(unix_gc_wait, !READ_ONCE(gc_in_progress));
 }
 
 /* The external entry point: unix_gc() */