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[PATCH 3/3] Add runtime check for __ASSUME_REQUEUE_PI (BZ#18463)
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Wed, 18 May 2016 18:57:18 -0300
- Subject: [PATCH 3/3] Add runtime check for __ASSUME_REQUEUE_PI (BZ#18463)
- Authentication-results: sourceware.org; auth=none
- References: <1463608638-7215-1-git-send-email-adhemerval dot zanella at linaro dot org>
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).
It fixes BZ#18463 since now requeue pi operation are queried on runtime.
Tested on ARM (v3.8 kernel) and x86_64.
* nptl/pthreadP.h (prio_inherit_missing): Add prototype.
(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.
---
ChangeLog | 18 ++++++++++++++++++
nptl/pthreadP.h | 23 ++++++++++++++---------
nptl/pthread_cond_broadcast.c | 5 ++---
nptl/pthread_cond_signal.c | 5 ++---
nptl/pthread_cond_timedwait.c | 11 ++++-------
nptl/pthread_cond_wait.c | 13 +++++--------
nptl/pthread_mutex_init.c | 2 +-
7 files changed, 46 insertions(+), 31 deletions(-)
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index d479a3e..4eac061 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -585,17 +585,22 @@ 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 552fd42..ef81bcd 100644
--- a/nptl/pthread_cond_broadcast.c
+++ b/nptl/pthread_cond_broadcast.c
@@ -60,9 +60,8 @@ __pthread_cond_broadcast (pthread_cond_t *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 b3a6d3d..9c8f883 100644
--- a/nptl/pthread_cond_signal.c
+++ b/nptl/pthread_cond_signal.c
@@ -46,11 +46,10 @@ __pthread_cond_signal (pthread_cond_t *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 711a51d..61a651c 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 3f62acc..f79bf67 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 6aef890..c4f45f2 100644
--- a/nptl/pthread_mutex_init.c
+++ b/nptl/pthread_mutex_init.c
@@ -33,7 +33,7 @@ static const struct pthread_mutexattr default_mutexattr =
};
-static bool
+bool
prio_inherit_missing (void)
{
#ifdef __NR_futex
--
2.7.4