New futex(2) based rwlock implementation based on the mutex code.

This implementation reduces contention because threads no longer need
to spin calling sched_yield(2) before going to sleep.

Tested by many, thanks!

ok visa@, pirofti@

1 files changed, 12 insertions, 1 deletions

diff --git a/src/lib/libc/include/thread_private.h b/src/lib/libc/include/thread_private.h
index 774e0cba1f..98dfaa6322 100644
--- a/src/lib/libc/include/thread_private.h
+++ b/src/lib/libc/include/thread_private.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: thread_private.h,v 1.34 2019/01/10 18:45:33 otto Exp $ */
+/* $OpenBSD: thread_private.h,v 1.35 2019/02/13 13:22:14 mpi Exp $ */
 
 /* PUBLIC DOMAIN: No Rights Reserved. Marco S Hyman <marc@snafu.org> */
 
@@ -298,6 +298,10 @@ struct pthread_cond {
         struct pthread_mutex *mutex;
 };
 
+struct pthread_rwlock {
+        volatile unsigned int value;
+};
+
 #else
 
 struct pthread_mutex {
@@ -315,6 +319,13 @@ struct pthread_cond {
         struct pthread_mutex *mutex;
         clockid_t clock;
 };
+
+struct pthread_rwlock {
+        _atomic_lock_t lock;
+        pthread_t owner;
+        struct pthread_queue writers;
+        int readers;
+};
 #endif /* FUTEX */
 
 struct pthread_mutex_attr {