Add runtime check for __ASSUME_REQUEUE_PI (BZ# 18463)

This patch adds a runtime check for requeue priority futexes
(FUTEX_{WAIT,CMP}_REQUEUE_PI) for configurations that do not define
__ASSUME_REQUEUE_PI.

It uses the same check uses for priority lock/unlock support, where
issuing a futex operation with FUTEX_UNLOCK_PI returns if kernel has
or not internal 'futex_cmpxchg_enabled' support (which is also used
on requeue priority futexes operations).

For architectures that already have __ASSUME_REQUEUE_PI the code
flow does not change, 'use_requeue_pi' returns the previous chec
logic.  Also, if 'futex_cmpxchg_enabled' is not supported by the
kernel, the previous logic will be used (by issuing a default futex
operation).

Tested on ARM (v3.8 kernel) and x86_64.

	* nptl/pthreadP.h (prio_inherit_missing): Change name to
	__prio_inherit_missing.
	(USE_REQUEUE_PI): Remove define.
	(use_requeue_pi): New function.
	* nptl/pthread_cond_broadcast.c [__ASSUME_REQUEUE_PI]
	(__pthread_cond_broadcast): Remove ifdef.
	(USE_REQUEUE_PI): Change to use_requeue_pi.
	* nptl/pthread_cond_signal.c [__ASSUME_REQUEUE_PI]
	(__pthread_cond_signal): Remove ifdef.
	(USE_REQUEUE_PI): Change to use_requeue_pi.
	* nptl/pthread_cond_timedwait.c [__ASSUME_REQUEUE_PI]
	(__pthread_cond_timedwait): Remove ifdef.
	(USE_REQUEUE_PI): Change to use_requeue_pi.
	( nptl/pthread_cond_wait.c [__ASSUME_REQUEUE_PI]
	(__pthread_cond_wait): Remove ifdef.
	(USE_REQUEUE_PI): Change to use_requeue_pi.
	* nptl/pthread_mutex_init.c (prio_inherit_missing): Remove 'static'
	qualifier and change name to __prio_inherit_missing.

7 files changed, 50 insertions, 33 deletions

diff --git a/ChangeLog b/ChangeLog
index aadf824afe..4f035c460d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,25 @@
 
 2016-06-03  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
+	* nptl/pthreadP.h (prio_inherit_missing): Change name to
+	__prio_inherit_missing.
+	(USE_REQUEUE_PI): Remove define.
+	(use_requeue_pi): New function.
+	* nptl/pthread_cond_broadcast.c [__ASSUME_REQUEUE_PI]
+	(__pthread_cond_broadcast): Remove ifdef.
+	(USE_REQUEUE_PI): Change to use_requeue_pi.
+	* nptl/pthread_cond_signal.c [__ASSUME_REQUEUE_PI]
+	(__pthread_cond_signal): Remove ifdef.
+	(USE_REQUEUE_PI): Change to use_requeue_pi.
+	* nptl/pthread_cond_timedwait.c [__ASSUME_REQUEUE_PI]
+	(__pthread_cond_timedwait): Remove ifdef.
+	(USE_REQUEUE_PI): Change to use_requeue_pi.
+	( nptl/pthread_cond_wait.c [__ASSUME_REQUEUE_PI]
+	(__pthread_cond_wait): Remove ifdef.
+	(USE_REQUEUE_PI): Change to use_requeue_pi.
+	* nptl/pthread_mutex_init.c (prio_inherit_missing): Remove 'static'
+	qualifier and change name to __prio_inherit_missing.
+
 	* nptl/nptl-init.c [__ASSUME_SET_ROBUST_LIST]
 	(__set_robust_list_avail): Remove define.
 	[__NR_set_robust_list] (__pthread_initialize_minimal_internal):
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index a4a6ee1906..ee52b0c601 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -580,17 +580,22 @@ extern void __wait_lookup_done (void) attribute_hidden;
 # define PTHREAD_STATIC_FN_REQUIRE(name) __asm (".globl " #name);
 #endif
 
+extern bool __prio_inherit_missing (void);
+
 /* Test if the mutex is suitable for the FUTEX_WAIT_REQUEUE_PI operation.  */
-#if (defined lll_futex_wait_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
-# define USE_REQUEUE_PI(mut) \
-   ((mut) && (mut) != (void *) ~0l \
-    && (((mut)->__data.__kind \
-	 & (PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_ROBUST_NORMAL_NP)) \
-	== PTHREAD_MUTEX_PRIO_INHERIT_NP))
-#else
-# define USE_REQUEUE_PI(mut) 0
+static inline bool
+use_requeue_pi (pthread_mutex_t *mut)
+{
+#ifndef __ASSUME_REQUEUE_PI
+  if (__prio_inherit_missing ())
+    return false;
 #endif
+  return (mut) &&
+    (mut) != (void *) ~0l &&
+    (((mut)->__data.__kind
+      & (PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_ROBUST_NORMAL_NP)) ==
+     PTHREAD_MUTEX_PRIO_INHERIT_NP);
+}
 
 /* Returns 0 if POL is a valid scheduling policy.  */
 static inline int
diff --git a/nptl/pthread_cond_broadcast.c b/nptl/pthread_cond_broadcast.c
index 881d098c05..ce75b3c7cd 100644
--- a/nptl/pthread_cond_broadcast.c
+++ b/nptl/pthread_cond_broadcast.c
@@ -61,9 +61,8 @@ __pthread_cond_broadcast (cond)
 	  || PTHREAD_MUTEX_PSHARED (mut) & PTHREAD_MUTEX_PSHARED_BIT)
 	goto wake_all;
 
-#if (defined lll_futex_cmp_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
-      if (USE_REQUEUE_PI (mut))
+#ifdef lll_futex_cmp_requeue_pi
+      if (use_requeue_pi (mut))
 	{
 	  if (lll_futex_cmp_requeue_pi (&cond->__data.__futex, 1, INT_MAX,
 					&mut->__data.__lock, futex_val,
diff --git a/nptl/pthread_cond_signal.c b/nptl/pthread_cond_signal.c
index ba32f40532..0133ffe825 100644
--- a/nptl/pthread_cond_signal.c
+++ b/nptl/pthread_cond_signal.c
@@ -47,11 +47,10 @@ __pthread_cond_signal (cond)
       ++cond->__data.__wakeup_seq;
       ++cond->__data.__futex;
 
-#if (defined lll_futex_cmp_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
+#ifdef lll_futex_cmp_requeue_pi
       pthread_mutex_t *mut = cond->__data.__mutex;
 
-      if (USE_REQUEUE_PI (mut)
+      if (use_requeue_pi (mut)
 	/* This can only really fail with a ENOSYS, since nobody can modify
 	   futex while we have the cond_lock.  */
 	  && lll_futex_cmp_requeue_pi (&cond->__data.__futex, 1, 0,
diff --git a/nptl/pthread_cond_timedwait.c b/nptl/pthread_cond_timedwait.c
index bf80467845..3553b362e6 100644
--- a/nptl/pthread_cond_timedwait.c
+++ b/nptl/pthread_cond_timedwait.c
@@ -63,8 +63,7 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
   int pshared = (cond->__data.__mutex == (void *) ~0l)
 		? LLL_SHARED : LLL_PRIVATE;
 
-#if (defined lll_futex_timed_wait_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
+#ifdef lll_futex_timed_wait_requeue_pi
   int pi_flag = 0;
 #endif
 
@@ -161,8 +160,7 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
 
 /* REQUEUE_PI was implemented after FUTEX_CLOCK_REALTIME, so it is sufficient
    to check just the former.  */
-#if (defined lll_futex_timed_wait_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
+#ifdef lll_futex_timed_wait_requeue_pi
       /* If pi_flag remained 1 then it means that we had the lock and the mutex
 	 but a spurious waker raced ahead of us.  Give back the mutex before
 	 going into wait again.  */
@@ -171,7 +169,7 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
 	  __pthread_mutex_cond_lock_adjust (mutex);
 	  __pthread_mutex_unlock_usercnt (mutex, 0);
 	}
-      pi_flag = USE_REQUEUE_PI (mutex);
+      pi_flag = use_requeue_pi (mutex);
 
       if (pi_flag)
 	{
@@ -250,8 +248,7 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
   __pthread_cleanup_pop (&buffer, 0);
 
   /* Get the mutex before returning.  */
-#if (defined lll_futex_timed_wait_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
+#ifdef lll_futex_timed_wait_requeue_pi
   if (pi_flag)
     {
       __pthread_mutex_cond_lock_adjust (mutex);
diff --git a/nptl/pthread_cond_wait.c b/nptl/pthread_cond_wait.c
index 0d6558b642..9db01d243d 100644
--- a/nptl/pthread_cond_wait.c
+++ b/nptl/pthread_cond_wait.c
@@ -86,7 +86,7 @@ __condvar_cleanup (void *arg)
 
   /* Get the mutex before returning unless asynchronous cancellation
      is in effect.  We don't try to get the mutex if we already own it.  */
-  if (!(USE_REQUEUE_PI (cbuffer->mutex))
+  if (!(use_requeue_pi (cbuffer->mutex))
       || ((cbuffer->mutex->__data.__lock & FUTEX_TID_MASK)
 	  != THREAD_GETMEM (THREAD_SELF, tid)))
   {
@@ -106,8 +106,7 @@ __pthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex)
   int pshared = (cond->__data.__mutex == (void *) ~0l)
 		? LLL_SHARED : LLL_PRIVATE;
 
-#if (defined lll_futex_wait_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
+#ifdef lll_futex_wait_requeue_pi
   int pi_flag = 0;
 #endif
 
@@ -160,8 +159,7 @@ __pthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex)
       /* Enable asynchronous cancellation.  Required by the standard.  */
       cbuffer.oldtype = __pthread_enable_asynccancel ();
 
-#if (defined lll_futex_wait_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
+#ifdef lll_futex_wait_requeue_pi
       /* If pi_flag remained 1 then it means that we had the lock and the mutex
 	 but a spurious waker raced ahead of us.  Give back the mutex before
 	 going into wait again.  */
@@ -170,7 +168,7 @@ __pthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex)
 	  __pthread_mutex_cond_lock_adjust (mutex);
 	  __pthread_mutex_unlock_usercnt (mutex, 0);
 	}
-      pi_flag = USE_REQUEUE_PI (mutex);
+      pi_flag = use_requeue_pi (mutex);
 
       if (pi_flag)
 	{
@@ -221,8 +219,7 @@ __pthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex)
   __pthread_cleanup_pop (&buffer, 0);
 
   /* Get the mutex before returning.  Not needed for PI.  */
-#if (defined lll_futex_wait_requeue_pi \
-     && defined __ASSUME_REQUEUE_PI)
+#ifdef lll_futex_wait_requeue_pi
   if (pi_flag)
     {
       __pthread_mutex_cond_lock_adjust (mutex);
diff --git a/nptl/pthread_mutex_init.c b/nptl/pthread_mutex_init.c
index 2bc1f881fa..3e4c06e9f9 100644
--- a/nptl/pthread_mutex_init.c
+++ b/nptl/pthread_mutex_init.c
@@ -33,8 +33,9 @@ static const struct pthread_mutexattr default_mutexattr =
   };
 
 
-static bool
-prio_inherit_missing (void)
+bool
+attribute_hidden
+__prio_inherit_missing (void)
 {
 #ifdef __NR_futex
   static int tpi_supported;
@@ -73,7 +74,7 @@ __pthread_mutex_init (mutex, mutexattr)
       break;
 
     case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
-      if (__glibc_unlikely (prio_inherit_missing ()))
+      if (__glibc_unlikely (__prio_inherit_missing ()))
 	return ENOTSUP;
       break;