bionic: pthread: use private futexes by default for mutexes and condvars

Private futexes are a recent kernel addition: faster futexes that cannot be
shared between processes. This patch uses them by default, unless the PROCESS_SHARED
attribute flag is used when creating a mutex and/or conditional variable.

Also introduces pthread_condattr_init/destroy/setpshared/getpshared.

Change-Id: I3a0e2116f467072b046524cb5babc00e41057a53

1 files changed, 18 insertions, 0 deletions

diff --git a/libc/arch-sh/bionic/atomics_sh.c b/libc/arch-sh/bionic/atomics_sh.c
index 16966f7..5171363 100644
--- a/libc/arch-sh/bionic/atomics_sh.c
+++ b/libc/arch-sh/bionic/atomics_sh.c
@@ -98,3 +98,21 @@ int __futex_wake(volatile void *ftx, int count)
 {
     return futex(ftx, FUTEX_WAKE, count, NULL, NULL, 0);
 }
+
+/* Private futexes belong to a single address space and cannot be
+ * shared among processes. They are however significantly faster to
+ * operate than standard futexes.
+ */
+#define FUTEX_PRIVATE_FLAG  128
+#define FUTEX_WAIT_PRIVATE  (FUTEX_WAIT|FUTEX_PRIVATE_FLAG)
+#define FUTEX_WAKE_PRIVATE  (FUTEX_WAKE|FUTEX_PRIVATE_FLAG)
+
+int __futex_wait_private(volatile void *ftx, int val, const struct timespec *timeout)
+{
+    return futex(ftx, FUTEX_WAIT_PRIVATE, val, (void *)timeout, NULL, 0);
+}
+
+int __futex_wake_private(volatile void *ftx, int count)
+{
+    return futex(ftx, FUTEX_WAKE_PRIVATE, count, NULL, NULL, 0);
+}