Use critical sections as mutex implementation on Windows

Windows native critical sections are now used internally in the
runtime system as mutex implementation. This since they perform
better under extreme contention than our own implementation.

1 files changed, 10 insertions, 0 deletions

diff --git a/erts/emulator/beam/erl_smp.h b/erts/emulator/beam/erl_smp.h
index a89ddfbcc1..63179dfad4 100644
--- a/erts/emulator/beam/erl_smp.h
+++ b/erts/emulator/beam/erl_smp.h
@@ -822,6 +822,16 @@ erts_smp_cnd_wait(erts_smp_cnd_t *cnd, erts_smp_mtx_t *mtx)
 #endif
 }
 
+/*
+ * IMPORTANT note about erts_smp_cnd_signal() and erts_smp_cnd_broadcast()
+ *
+ * POSIX allow a call to `pthread_cond_signal' or `pthread_cond_broadcast'
+ * even though the associated mutex/mutexes isn't/aren't locked by the
+ * caller. Our implementation do not allow that in order to avoid a
+ * performance penalty. That is, all associated mutexes *need* to be
+ * locked by the caller of erts_smp_cnd_signal()/erts_smp_cnd_broadcast()!
+ */
+
 ERTS_GLB_INLINE void
 erts_smp_cnd_signal(erts_smp_cnd_t *cnd)
 {