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

This reverts commit ba9c6f0989ae94778ba2b9f597adc827c9dc81e8.

6 files changed, 298 insertions, 611 deletions

diff --git a/libc/arch-arm/bionic/atomics_arm.S b/libc/arch-arm/bionic/atomics_arm.S
index 5076fe360..55c642f8d 100644
--- a/libc/arch-arm/bionic/atomics_arm.S
+++ b/libc/arch-arm/bionic/atomics_arm.S
@@ -43,19 +43,6 @@
 #define FUTEX_WAIT 0
 #define FUTEX_WAKE 1
 
-/* Private futexes belong to a single address space and cannot be
- * shared among processes. They are however significantly faster to
- * operate than standard futexes.
- */
-.global __futex_wait_private
-.type __futex_wait_private, %function
-.global __futex_wake_private
-.type __futex_wake_private, %function
-
-#define FUTEX_PRIVATE_FLAG  128
-#define FUTEX_WAIT_PRIVATE  (FUTEX_WAIT|FUTEX_PRIVATE_FLAG)
-#define FUTEX_WAKE_PRIVATE  (FUTEX_WAKE|FUTEX_PRIVATE_FLAG)
-
 #if 1
    .equ     kernel_cmpxchg, 0xFFFF0FC0
    .equ     kernel_atomic_base, 0xFFFF0FFF
@@ -198,28 +185,6 @@ __futex_wake:
     ldmia   sp!, {r4, r7}
     bx      lr
 
-__futex_wait_private:
-    .fnstart
-    stmdb   sp!, {r4, r7}
-    .save   {r4, r7}
-    mov     r3, r2
-    mov     r2, r1
-    mov     r1, #FUTEX_WAIT_PRIVATE
-    ldr     r7, =__NR_futex
-    swi     #0
-    ldmia   sp!, {r4, r7}
-    bx      lr
-    .fnend
-
-__futex_wake_private:
-    stmdb   sp!, {r4, r7}
-    mov     r2, r1
-    mov     r1, #FUTEX_WAKE_PRIVATE
-    ldr     r7, =__NR_futex
-    swi     #0
-    ldmia   sp!, {r4, r7}
-    bx      lr
-
 #else
 
 __futex_wait:
@@ -235,17 +200,4 @@ __futex_wake:
     swi     #__NR_futex
     bx      lr
 
-__futex_wait_private:
-    mov     r3, r2
-    mov     r2, r1
-    mov     r1, #FUTEX_WAIT_PRIVATE
-    swi     #__NR_futex
-    bx      lr
-
-__futex_wake_private:
-    mov     r2, r1
-    mov     r1, #FUTEX_WAKE_PRIVATE
-    swi     #__NR_futex
-    bx      lr
-
 #endif
diff --git a/libc/arch-sh/bionic/atomics_sh.c b/libc/arch-sh/bionic/atomics_sh.c
index 51713634c..16966f762 100644
--- a/libc/arch-sh/bionic/atomics_sh.c
+++ b/libc/arch-sh/bionic/atomics_sh.c
@@ -98,21 +98,3 @@ 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);
-}
diff --git a/libc/arch-x86/bionic/atomics_x86.c b/libc/arch-x86/bionic/atomics_x86.c
index d6e3247d8..b7b20e6ef 100644
--- a/libc/arch-x86/bionic/atomics_x86.c
+++ b/libc/arch-x86/bionic/atomics_x86.c
@@ -60,43 +60,6 @@ int __futex_wake(volatile void *ftx, int count)
     return ret;
 }
 
-/* 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)
-{
-    int ret;
-    asm volatile (
-        "int $0x80;"
-        : "=a" (ret)
-        : "0" (FUTEX_SYSCALL),
-          "b" (ftx),
-          "c" (FUTEX_WAIT_PRIVATE),
-          "d" (val),
-          "S" (0)
-    );
-    return ret;
-}
-
-int __futex_wake_private(volatile void *ftx, int count)
-{
-    int ret;
-    asm volatile (
-        "int $0x80;"
-        : "=a" (ret)
-        : "0" (FUTEX_SYSCALL),
-          "b" (ftx),
-          "c" (FUTEX_WAKE_PRIVATE),
-          "d" (count)
-    );
-    return ret;
-}
-
 int __atomic_cmpxchg(int old, int new, volatile int* addr) {
     int xchg;
     asm volatile (
diff --git a/libc/bionic/pthread.c b/libc/bionic/pthread.c
index 6a6386833..c1a6a8aaa 100644
--- a/libc/bionic/pthread.c
+++ b/libc/bionic/pthread.c
@@ -44,9 +44,6 @@
 #include <assert.h>
 #include <malloc.h>
 
-#define  __likely(cond)    __builtin_expect(!!(cond), 1)
-#define  __unlikely(cond)  __builtin_expect(!!(cond), 0)
-
 extern int  __pthread_clone(int (*fn)(void*), void *child_stack, int flags, void *arg);
 extern void _exit_with_stack_teardown(void * stackBase, int stackSize, int retCode);
 extern void _exit_thread(int  retCode);
@@ -715,9 +712,6 @@ int pthread_setschedparam(pthread_t thid, int policy,
 int __futex_wait(volatile void *ftx, int val, const struct timespec *timeout);
 int __futex_wake(volatile void *ftx, int count);
 
-int __futex_wait_private(volatile void *ftx, int val, const struct timespec *timeout);
-int __futex_wake_private(volatile void *ftx, int count);
-
 // mutex lock states
 //
 // 0: unlocked
@@ -729,8 +723,7 @@ int __futex_wake_private(volatile void *ftx, int count);
  * bits:     name     description
  * 31-16     tid      owner thread's kernel id (recursive and errorcheck only)
  * 15-14     type     mutex type
- * 13        sharing  sharing flag
- * 12-2      counter  counter of recursive mutexes
+ * 13-2      counter  counter of recursive mutexes
  * 1-0       state    lock state (0, 1 or 2)
  */
 
@@ -744,21 +737,10 @@ int __futex_wake_private(volatile void *ftx, int count);
 #define  MUTEX_TYPE_ERRORCHECK 0x8000
 
 #define  MUTEX_COUNTER_SHIFT  2
-#define  MUTEX_COUNTER_MASK   0x1ffc
+#define  MUTEX_COUNTER_MASK   0x3ffc
 
-#define  MUTEX_SHARING_MASK   0x2000
 
-#define  MUTEX_IS_SHARED(m)  (((m)->value & MUTEX_SHARING_MASK) != 0)
 
-/* A mutex attribute stores the following in its fields:
- *
- * bits:    name     description
- * 0-3      type     type of thread (NORMAL/RECURSIVE/ERRORCHECK)
- * 4        sharing  1 if shared, or 0 otherwise.
- */
-
-#define MUTEXATTR_TYPE_MASK     0x0007
-#define MUTEXATTR_SHARING_MASK  0x0010
 
 int pthread_mutexattr_init(pthread_mutexattr_t *attr)
 {
@@ -782,12 +764,10 @@ int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
 
 int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type)
 {
-    if (attr) {
-        int  atype = (*attr & MUTEXATTR_TYPE_MASK);
-        if (atype >= PTHREAD_MUTEX_NORMAL && atype <= PTHREAD_MUTEX_ERRORCHECK) {
-            *type = atype;
-            return 0;
-        }
+    if (attr && *attr >= PTHREAD_MUTEX_NORMAL &&
+                *attr <= PTHREAD_MUTEX_ERRORCHECK ) {
+        *type = *attr;
+        return 0;
     }
     return EINVAL;
 }
@@ -796,7 +776,7 @@ int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type)
 {
     if (attr && type >= PTHREAD_MUTEX_NORMAL &&
                 type <= PTHREAD_MUTEX_ERRORCHECK ) {
-        *attr = (*attr & ~MUTEXATTR_TYPE_MASK) | type;
+        *attr = type;
         return 0;
     }
     return EINVAL;
@@ -811,70 +791,54 @@ int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int  pshared)
 
     switch (pshared) {
     case PTHREAD_PROCESS_PRIVATE:
-        *attr &= ~MUTEXATTR_SHARING_MASK;
-        return 0;
-
     case PTHREAD_PROCESS_SHARED:
         /* our current implementation of pthread actually supports shared
          * mutexes but won't cleanup if a process dies with the mutex held.
          * Nevertheless, it's better than nothing. Shared mutexes are used
          * by surfaceflinger and audioflinger.
          */
-        *attr |= MUTEXATTR_SHARING_MASK;
         return 0;
     }
 
-    return EINVAL;
+    return ENOTSUP;
 }
 
 int pthread_mutexattr_getpshared(pthread_mutexattr_t *attr, int *pshared)
 {
-    if (!attr || !pshared)
+    if (!attr)
         return EINVAL;
 
-    *pshared = (*attr & MUTEXATTR_SHARING_MASK) ? PTHREAD_PROCESS_SHARED
-                                                : PTHREAD_PROCESS_PRIVATE;
+    *pshared = PTHREAD_PROCESS_PRIVATE;
     return 0;
 }
 
 int pthread_mutex_init(pthread_mutex_t *mutex,
                        const pthread_mutexattr_t *attr)
 {
-    int value = 0;
-
-    if (__unlikely(mutex == NULL))
-        return EINVAL;
+    if ( mutex ) {
+        if (attr == NULL) {
+            mutex->value = MUTEX_TYPE_NORMAL;
+            return 0;
+        }
+        switch ( *attr ) {
+        case PTHREAD_MUTEX_NORMAL:
+            mutex->value = MUTEX_TYPE_NORMAL;
+            return 0;
 
-    if (__likely(attr == NULL)) {
-        mutex->value = MUTEX_TYPE_NORMAL;
-        return 0;
-    }
+        case PTHREAD_MUTEX_RECURSIVE:
+            mutex->value = MUTEX_TYPE_RECURSIVE;
+            return 0;
 
-    if ((*attr & MUTEXATTR_SHARING_MASK) != 0)
-        value |= MUTEX_SHARING_MASK;
-
-    switch (*attr & MUTEXATTR_TYPE_MASK) {
-    case PTHREAD_MUTEX_NORMAL:
-        value |= MUTEX_TYPE_NORMAL;
-        break;
-    case PTHREAD_MUTEX_RECURSIVE:
-        value |= MUTEX_TYPE_RECURSIVE;
-        break;
-    case PTHREAD_MUTEX_ERRORCHECK:
-        value |= MUTEX_TYPE_ERRORCHECK;
-        break;
-    default:
-        return EINVAL;
+        case PTHREAD_MUTEX_ERRORCHECK:
+            mutex->value = MUTEX_TYPE_ERRORCHECK;
+            return 0;
+        }
     }
-    mutex->value = value;
-    return 0;
+    return EINVAL;
 }
 
 int pthread_mutex_destroy(pthread_mutex_t *mutex)
 {
-    if (__unlikely(mutex == NULL))
-        return EINVAL;
-
     mutex->value = 0xdead10cc;
     return 0;
 }
@@ -891,46 +855,35 @@ int pthread_mutex_destroy(pthread_mutex_t *mutex)
  * Non-recursive mutexes don't use the thread-id or counter fields, and the
  * "type" value is zero, so the only bits that will be set are the ones in
  * the lock state field.
- *
- * This routine is used for both shared and private mutexes.
  */
 static __inline__ void
 _normal_lock(pthread_mutex_t*  mutex)
 {
-    if (__likely(!MUTEX_IS_SHARED(mutex))) {
+    /*
+     * The common case is an unlocked mutex, so we begin by trying to
+     * change the lock's state from 0 to 1.  __atomic_cmpxchg() returns 0
+     * if it made the swap successfully.  If the result is nonzero, this
+     * lock is already held by another thread.
+     */
+    if (__atomic_cmpxchg(0, 1, &mutex->value ) != 0) {
         /*
-        * The common case is an unlocked mutex, so we begin by trying to
-        * change the lock's state from 0 to 1.  __atomic_cmpxchg() returns 0
-        * if it made the swap successfully.  If the result is nonzero, this
-        * lock is already held by another thread.
-        */
-        if (__atomic_cmpxchg(0, 1, &mutex->value) != 0) {
-            /*
-            * We want to go to sleep until the mutex is available, which
-            * requires promoting it to state 2.  We need to swap in the new
-            * state value and then wait until somebody wakes us up.
-            *
-            * __atomic_swap() returns the previous value.  We swap 2 in and
-            * see if we got zero back; if so, we have acquired the lock.  If
-            * not, another thread still holds the lock and we wait again.
-            *
-            * The second argument to the __futex_wait() call is compared
-            * against the current value.  If it doesn't match, __futex_wait()
-            * returns immediately (otherwise, it sleeps for a time specified
-            * by the third argument; 0 means sleep forever).  This ensures
-            * that the mutex is in state 2 when we go to sleep on it, which
-            * guarantees a wake-up call.
-            */
-            while (__atomic_swap(2, &mutex->value ) != 0)
-                __futex_wait_private(&mutex->value, 2, 0);
-        }
-    } else {
-        /* Same algorithm, with the sharing bit flag set */
-        const int sharing = MUTEX_SHARING_MASK;
-        if (__atomic_cmpxchg(sharing|0, sharing|1, &mutex->value) != 0) {
-            while (__atomic_swap(sharing|2, &mutex->value ) != (sharing|0))
-                __futex_wait(&mutex->value, sharing|2, 0);
-        }
+         * We want to go to sleep until the mutex is available, which
+         * requires promoting it to state 2.  We need to swap in the new
+         * state value and then wait until somebody wakes us up.
+         *
+         * __atomic_swap() returns the previous value.  We swap 2 in and
+         * see if we got zero back; if so, we have acquired the lock.  If
+         * not, another thread still holds the lock and we wait again.
+         *
+         * The second argument to the __futex_wait() call is compared
+         * against the current value.  If it doesn't match, __futex_wait()
+         * returns immediately (otherwise, it sleeps for a time specified
+         * by the third argument; 0 means sleep forever).  This ensures
+         * that the mutex is in state 2 when we go to sleep on it, which
+         * guarantees a wake-up call.
+         */
+        while (__atomic_swap(2, &mutex->value ) != 0)
+            __futex_wait(&mutex->value, 2, 0);
     }
 }
 
@@ -941,59 +894,50 @@ _normal_lock(pthread_mutex_t*  mutex)
 static __inline__ void
 _normal_unlock(pthread_mutex_t*  mutex)
 {
-    if (__likely(!MUTEX_IS_SHARED(mutex))) {
+    /*
+     * The mutex value will be 1 or (rarely) 2.  We use an atomic decrement
+     * to release the lock.  __atomic_dec() returns the previous value;
+     * if it wasn't 1 we have to do some additional work.
+     */
+    if (__atomic_dec(&mutex->value) != 1) {
         /*
-        * The mutex value will be 1 or (rarely) 2.  We use an atomic decrement
-        * to release the lock.  __atomic_dec() returns the previous value;
-        * if it wasn't 1 we have to do some additional work.
-        */
-        if (__atomic_dec(&mutex->value) != 1) {
-            /*
-            * Start by releasing the lock.  The decrement changed it from
-            * "contended lock" to "uncontended lock", which means we still
-            * hold it, and anybody who tries to sneak in will push it back
-            * to state 2.
-            *
-            * Once we set it to zero the lock is up for grabs.  We follow
-            * this with a __futex_wake() to ensure that one of the waiting
-            * threads has a chance to grab it.
-            *
-            * This doesn't cause a race with the swap/wait pair in
-            * _normal_lock(), because the __futex_wait() call there will
-            * return immediately if the mutex value isn't 2.
-            */
-            mutex->value = 0;
-
-            /*
-            * Wake up one waiting thread.  We don't know which thread will be
-            * woken or when it'll start executing -- futexes make no guarantees
-            * here.  There may not even be a thread waiting.
-            *
-            * The newly-woken thread will replace the 0 we just set above
-            * with 2, which means that when it eventually releases the mutex
-            * it will also call FUTEX_WAKE.  This results in one extra wake
-            * call whenever a lock is contended, but lets us avoid forgetting
-            * anyone without requiring us to track the number of sleepers.
-            *
-            * It's possible for another thread to sneak in and grab the lock
-            * between the zero assignment above and the wake call below.  If
-            * the new thread is "slow" and holds the lock for a while, we'll
-            * wake up a sleeper, which will swap in a 2 and then go back to
-            * sleep since the lock is still held.  If the new thread is "fast",
-            * running to completion before we call wake, the thread we
-            * eventually wake will find an unlocked mutex and will execute.
-            * Either way we have correct behavior and nobody is orphaned on
-            * the wait queue.
-            */
-            __futex_wake_private(&mutex->value, 1);
-        }
-    } else {
-        /* Same algorithm with sharing bit flag set */
-        const int sharing = MUTEX_SHARING_MASK;
-        if (__atomic_dec(&mutex->value) != (sharing|1)) {
-            mutex->value = sharing;
-            __futex_wake(&mutex->value, 1);
-        }
+         * Start by releasing the lock.  The decrement changed it from
+         * "contended lock" to "uncontended lock", which means we still
+         * hold it, and anybody who tries to sneak in will push it back
+         * to state 2.
+         *
+         * Once we set it to zero the lock is up for grabs.  We follow
+         * this with a __futex_wake() to ensure that one of the waiting
+         * threads has a chance to grab it.
+         *
+         * This doesn't cause a race with the swap/wait pair in
+         * _normal_lock(), because the __futex_wait() call there will
+         * return immediately if the mutex value isn't 2.
+         */
+        mutex->value = 0;
+
+        /*
+         * Wake up one waiting thread.  We don't know which thread will be
+         * woken or when it'll start executing -- futexes make no guarantees
+         * here.  There may not even be a thread waiting.
+         *
+         * The newly-woken thread will replace the 0 we just set above
+         * with 2, which means that when it eventually releases the mutex
+         * it will also call FUTEX_WAKE.  This results in one extra wake
+         * call whenever a lock is contended, but lets us avoid forgetting
+         * anyone without requiring us to track the number of sleepers.
+         *
+         * It's possible for another thread to sneak in and grab the lock
+         * between the zero assignment above and the wake call below.  If
+         * the new thread is "slow" and holds the lock for a while, we'll
+         * wake up a sleeper, which will swap in a 2 and then go back to
+         * sleep since the lock is still held.  If the new thread is "fast",
+         * running to completion before we call wake, the thread we
+         * eventually wake will find an unlocked mutex and will execute.
+         * Either way we have correct behavior and nobody is orphaned on
+         * the wait queue.
+         */
+        __futex_wake(&mutex->value, 1);
     }
 }
 
@@ -1011,200 +955,173 @@ _recursive_unlock(void)
     _normal_unlock( &__recursive_lock );
 }
 
+#define  __likely(cond)    __builtin_expect(!!(cond), 1)
+#define  __unlikely(cond)  __builtin_expect(!!(cond), 0)
+
 int pthread_mutex_lock(pthread_mutex_t *mutex)
 {
-    int  mtype, tid, new_lock_type, sharing;
-
-    if (__unlikely(mutex == NULL))
-        return EINVAL;
-
-    /* get mutex type */
-    mtype = (mutex->value & MUTEX_TYPE_MASK);
-
-    /* Handle normal mutexes quickly */
-    if ( __likely(mtype == MUTEX_TYPE_NORMAL) ) {
-        _normal_lock(mutex);
-        return 0;
-    }
-
-    /* This is a recursive or error check mutex.
-     * Check that we don't already own it.
-     */
-    tid = __get_thread()->kernel_id;
-    if ( tid == MUTEX_OWNER(mutex) )
+    if (__likely(mutex != NULL))
     {
-        int  oldv, counter;
+        int  mtype = (mutex->value & MUTEX_TYPE_MASK);
 
-        if (mtype == MUTEX_TYPE_ERRORCHECK) {
-            /* trying to re-lock a mutex we already acquired */
-            return EDEADLK;
+        if ( __likely(mtype == MUTEX_TYPE_NORMAL) ) {
+            _normal_lock(mutex);
         }
-        /*
-         * We own the mutex, but other threads are able to change
-         * the contents (e.g. promoting it to "contended"), so we
-         * need to hold the global lock.
-         */
-        _recursive_lock();
-        oldv         = mutex->value;
-        counter      = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
-        mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
-        _recursive_unlock();
+        else
+        {
+            int  tid = __get_thread()->kernel_id;
 
-        return 0;
-    }
-
-    /* We don't own it, try to lock it.
-     * If the new lock is available immediately, we grab it in
-     * the "uncontended" state.
-     */
-    new_lock_type = 1;
-    sharing       = (mutex->value & MUTEX_SHARING_MASK);
-
-    mtype |= sharing;  /* restore sharing bit flag */
-
-    /* here, mtype corresponds to the uncontended value for the mutex,
-     * i.e. something like:
-     *
-     *  <tid=0><type=?><sharing=?><counter=0><state=0>
-     */
-
-    for (;;) {
-        int  oldv;
-
-        _recursive_lock();
-        oldv = mutex->value;
-        if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
-            mutex->value = ((tid << 16) | mtype | new_lock_type);
-        } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
-            oldv ^= 3;
-            mutex->value = oldv;
-        }
-        _recursive_unlock();
-
-        if (oldv == mtype)
-            break;
-
-        /*
-         * The lock was held, possibly contended by others.  From
-         * now on, if we manage to acquire the lock, we have to
-         * assume that others are still contending for it so that
-         * we'll wake them when we unlock it.
-         */
-        new_lock_type = 2;
+            if ( tid == MUTEX_OWNER(mutex) )
+            {
+                int  oldv, counter;
 
-        if (sharing) {
-            __futex_wait(&mutex->value, oldv, 0);
-        } else {
-            __futex_wait_private(&mutex->value, oldv, 0);
+                if (mtype == MUTEX_TYPE_ERRORCHECK) {
+                    /* trying to re-lock a mutex we already acquired */
+                    return EDEADLK;
+                }
+                /*
+                 * We own the mutex, but other threads are able to change
+                 * the contents (e.g. promoting it to "contended"), so we
+                 * need to hold the global lock.
+                 */
+                _recursive_lock();
+                oldv         = mutex->value;
+                counter      = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
+                mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
+                _recursive_unlock();
+            }
+            else
+            {
+                /*
+                 * If the new lock is available immediately, we grab it in
+                 * the "uncontended" state.
+                 */
+                int new_lock_type = 1;
+
+                for (;;) {
+                    int  oldv;
+
+                    _recursive_lock();
+                    oldv = mutex->value;
+                    if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
+                        mutex->value = ((tid << 16) | mtype | new_lock_type);
+                    } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
+                        oldv ^= 3;
+                        mutex->value = oldv;
+                    }
+                    _recursive_unlock();
+
+                    if (oldv == mtype)
+                        break;
+
+                    /*
+                     * The lock was held, possibly contended by others.  From
+                     * now on, if we manage to acquire the lock, we have to
+                     * assume that others are still contending for it so that
+                     * we'll wake them when we unlock it.
+                     */
+                    new_lock_type = 2;
+
+                    __futex_wait( &mutex->value, oldv, 0 );
+                }
+            }
         }
+        return 0;
     }
-    return 0;
+    return EINVAL;
 }
 
 
 int pthread_mutex_unlock(pthread_mutex_t *mutex)
 {
-    int mtype, tid, sharing, oldv;
-
-    if (__unlikely(mutex == NULL))
-        return EINVAL;
-
-    mtype = (mutex->value & MUTEX_TYPE_MASK);
-
-    if (__likely(mtype == MUTEX_TYPE_NORMAL)) {
-        _normal_unlock(mutex);
-        return 0;
-    }
-
-    tid     = __get_thread()->kernel_id;
-    sharing = (mutex->value & MUTEX_SHARING_MASK);
-
-    mtype |= sharing; /* restore sharing bit flag */
+    if (__likely(mutex != NULL))
+    {
+        int  mtype = (mutex->value & MUTEX_TYPE_MASK);
 
-    /* ensure that we own the mutex */
-    if (__unlikely(tid != MUTEX_OWNER(mutex)))
-        return EPERM;
+        if (__likely(mtype == MUTEX_TYPE_NORMAL)) {
+            _normal_unlock(mutex);
+        }
+        else
+        {
+            int  tid = __get_thread()->kernel_id;
 
-    /* decrement or unlock it */
-    _recursive_lock();
-    oldv = mutex->value;
-    if (oldv & MUTEX_COUNTER_MASK) {
-        /* decrement non-0 counter */
-        mutex->value = oldv - (1 << MUTEX_COUNTER_SHIFT);
-        oldv = 0;
-    } else {
-        /* counter was 0, revert to uncontended value */
-        mutex->value = mtype;
-    }
-    _recursive_unlock();
+            if ( tid == MUTEX_OWNER(mutex) )
+            {
+                int  oldv;
+
+                _recursive_lock();
+                oldv = mutex->value;
+                if (oldv & MUTEX_COUNTER_MASK) {
+                    mutex->value = oldv - (1 << MUTEX_COUNTER_SHIFT);
+                    oldv = 0;
+                } else {
+                    mutex->value = mtype;
+                }
+                _recursive_unlock();
 
-    /* if the mutex was contended, wake one waiting thread */
-    if ((oldv & 3) == 2) {
-        if (sharing) {
-            __futex_wake(&mutex->value, 1);
-        } else {
-            __futex_wake_private(&mutex->value, 1);
+                if ((oldv & 3) == 2)
+                    __futex_wake( &mutex->value, 1 );
+            }
+            else {
+                /* trying to unlock a lock we do not own */
+                return EPERM;
+            }
         }
+        return 0;
     }
-    return 0;
+    return EINVAL;
 }
 
 
 int pthread_mutex_trylock(pthread_mutex_t *mutex)
 {
-    int mtype, sharing, tid, oldv;
+    if (__likely(mutex != NULL))
+    {
+        int  mtype = (mutex->value & MUTEX_TYPE_MASK);
 
-    if (__unlikely(mutex == NULL))
-        return EINVAL;
+        if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
+        {
+            if (__atomic_cmpxchg(0, 1, &mutex->value) == 0)
+                return 0;
 
-    mtype = (mutex->value & MUTEX_TYPE_MASK);
+            return EBUSY;
+        }
+        else
+        {
+            int  tid = __get_thread()->kernel_id;
+            int  oldv;
 
-    /* handle normal mutex first */
-    if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
-    {
-        int sharing = (mutex->value & MUTEX_SHARING_MASK);
+            if ( tid == MUTEX_OWNER(mutex) )
+            {
+                int  oldv, counter;
 
-        if (__atomic_cmpxchg(sharing|0, sharing|1, &mutex->value) == 0)
-            return 0;
+                if (mtype == MUTEX_TYPE_ERRORCHECK) {
+                    /* already locked by ourselves */
+                    return EDEADLK;
+                }
 
-        return EBUSY;
-    }
+                _recursive_lock();
+                oldv = mutex->value;
+                counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
+                mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
+                _recursive_unlock();
+                return 0;
+            }
 
-    /* recursive or errorcheck mutex, do we already own it ? */
-    tid = __get_thread()->kernel_id;
-    sharing = mutex->value & MUTEX_SHARING_MASK;
+            /* try to lock it */
+            _recursive_lock();
+            oldv = mutex->value;
+            if (oldv == mtype)  /* uncontended released lock => state 1 */
+                mutex->value = ((tid << 16) | mtype | 1);
+            _recursive_unlock();
 
-    if ( tid == MUTEX_OWNER(mutex) )
-    {
-        int  counter;
+            if (oldv != mtype)
+                return EBUSY;
 
-        if (mtype == MUTEX_TYPE_ERRORCHECK) {
-            /* already locked by ourselves */
-            return EDEADLK;
+            return 0;
         }
-
-        _recursive_lock();
-        oldv = mutex->value;
-        counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
-        mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
-        _recursive_unlock();
-        return 0;
     }
-
-    /* we don't own it, so try to get it */
-    mtype |= sharing;
-
-    /* try to lock it */
-    _recursive_lock();
-    oldv = mutex->value;
-    if (oldv == mtype)  /* uncontended released lock => state 1 */
-        mutex->value = ((tid << 16) | mtype | 1);
-    _recursive_unlock();
-
-    if (oldv != mtype)
-        return EBUSY;
-
-    return 0;
+    return EINVAL;
 }
 
 
@@ -1247,21 +1164,16 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
     clockid_t        clock = CLOCK_MONOTONIC;
     struct timespec  abstime;
     struct timespec  ts;
-    int              mtype, tid, oldv, sharing, new_lock_type;
 
     /* compute absolute expiration time */
     __timespec_to_relative_msec(&abstime, msecs, clock);
 
-    if (__unlikely(mutex == NULL))
-        return EINVAL;
-
-
-    /* handle normal mutexes first */
-    mtype = (mutex->value & MUTEX_TYPE_MASK);
-
-    if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
+    if (__likely(mutex != NULL))
     {
-        if (__likely(!MUTEX_IS_SHARED(mutex))) {
+        int  mtype = (mutex->value & MUTEX_TYPE_MASK);
+
+        if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
+        {
             /* fast path for unconteded lock */
             if (__atomic_cmpxchg(0, 1, &mutex->value) == 0)
                 return 0;
@@ -1271,124 +1183,76 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
                 if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
                     return EBUSY;
 
-                __futex_wait_private(&mutex->value, 2, &ts);
-            }
-        } else /* sharing */ {
-            const int  sharing = MUTEX_SHARING_MASK;
-            if (__atomic_cmpxchg(sharing|0, sharing|1, &mutex->value) == 0)
-                return 0;
-
-            /* loop while needed */
-            while (__atomic_swap(sharing|2, &mutex->value) != (sharing|0)) {
-                if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
-                    return EBUSY;
-
-                __futex_wait(&mutex->value, sharing|2, &ts);
+                __futex_wait(&mutex->value, 2, &ts);
             }
+            return 0;
         }
-        return 0;
-    }
-
-    /* recursive or errorcheck - do we own the mutex ? */
-    tid = __get_thread()->kernel_id;
-
-    if ( tid == MUTEX_OWNER(mutex) )
-    {
-        int  counter;
-
-        if (mtype == MUTEX_TYPE_ERRORCHECK) {
-            /* already locked by ourselves */
-            return EDEADLK;
-        }
-
-        _recursive_lock();
-        oldv = mutex->value;
-        counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
-        mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
-        _recursive_unlock();
-        return 0;
-    }
-
-    /* we don't own it, try to lock it */
-    new_lock_type = 1;
-    sharing = (mutex->value & MUTEX_SHARING_MASK);
-
-    mtype |= sharing;
-
-    for (;;) {
-        struct timespec  ts;
-
-        _recursive_lock();
-        oldv = mutex->value;
-        if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
-            mutex->value = ((tid << 16) | mtype | new_lock_type);
-        } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
-            oldv ^= 3;
-            mutex->value = oldv;
-        }
-        _recursive_unlock();
+        else
+        {
+            int  tid = __get_thread()->kernel_id;
+            int  oldv;
 
-        if (oldv == mtype)
-            break;
-
-        /*
-         * The lock was held, possibly contended by others.  From
-         * now on, if we manage to acquire the lock, we have to
-         * assume that others are still contending for it so that
-         * we'll wake them when we unlock it.
-         */
-        new_lock_type = 2;
+            if ( tid == MUTEX_OWNER(mutex) )
+            {
+                int  oldv, counter;
 
-        if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
-            return EBUSY;
+                if (mtype == MUTEX_TYPE_ERRORCHECK) {
+                    /* already locked by ourselves */
+                    return EDEADLK;
+                }
 
-        if (sharing) {
-            __futex_wait(&mutex->value, oldv, &ts);
-        } else {
-            __futex_wait_private(&mutex->value, oldv, &ts);
+                _recursive_lock();
+                oldv = mutex->value;
+                counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
+                mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
+                _recursive_unlock();
+                return 0;
+            }
+            else
+            {
+                /*
+                 * If the new lock is available immediately, we grab it in
+                 * the "uncontended" state.
+                 */
+                int new_lock_type = 1;
+
+                for (;;) {
+                    int  oldv;
+                    struct timespec  ts;
+
+                    _recursive_lock();
+                    oldv = mutex->value;
+                    if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
+                        mutex->value = ((tid << 16) | mtype | new_lock_type);
+                    } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
+                        oldv ^= 3;
+                        mutex->value = oldv;
+                    }
+                    _recursive_unlock();
+
+                    if (oldv == mtype)
+                        break;
+
+                    /*
+                     * The lock was held, possibly contended by others.  From
+                     * now on, if we manage to acquire the lock, we have to
+                     * assume that others are still contending for it so that
+                     * we'll wake them when we unlock it.
+                     */
+                    new_lock_type = 2;
+
+                    if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
+                        return EBUSY;
+
+                    __futex_wait( &mutex->value, oldv, &ts );
+                }
+                return 0;
+            }
         }
     }
-    return 0;
-}
-
-
-int
-pthread_condattr_init(pthread_condattr_t *attr)
-{
-    *attr = PTHREAD_PROCESS_PRIVATE;
-    return 0;
-}
-
-int
-pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared)
-{
-    if (attr == NULL)
-        return EINVAL;
-
-    if (pshared != PTHREAD_PROCESS_PRIVATE &&
-        pshared != PTHREAD_PROCESS_SHARED)
-        return EINVAL;
-
-    *attr = pshared;
-    return 0;
-}
-
-int
-pthread_condattr_getpshared(pthread_condattr_t *attr, int *pshared)
-{
-    if (attr == NULL || pshared == NULL)
-        return EINVAL;
-
-    *pshared = *attr;
-    return 0;
+    return EINVAL;
 }
 
-int
-pthread_condattr_destroy(pthread_condattr_t *attr)
-{
-    *attr = 0xdeada11d;
-    return 0;
-}
 
 /* XXX *technically* there is a race condition that could allow
  * XXX a signal to be missed.  If thread A is preempted in _wait()
@@ -1398,29 +1262,10 @@ pthread_condattr_destroy(pthread_condattr_t *attr)
  * XXX then the signal will be lost.
  */
 
-/* Condition variables:
- * bits     name      description
- * 0        sharing   1 if process-shared, 0 if private
- * 2-31     counter   counter increment on each signal/broadcast
- */
-
-#define COND_SHARING_MASK       0x0001
-#define COND_COUNTER_INCREMENT  0x0002
-#define COND_COUNTER_MASK       (~COND_SHARING_MASK)
-
-#define  COND_IS_SHARED(cond) (((cond)->value & COND_SHARING_MASK) != 0)
-
 int pthread_cond_init(pthread_cond_t *cond,
                       const pthread_condattr_t *attr)
 {
-    if (cond == NULL)
-        return EINVAL;
-
     cond->value = 0;
-
-    if (attr != NULL && *attr == PTHREAD_PROCESS_SHARED)
-        cond->value |= COND_SHARING_MASK;
-
     return 0;
 }
 
@@ -1430,53 +1275,17 @@ int pthread_cond_destroy(pthread_cond_t *cond)
     return 0;
 }
 
-/* This function is used by pthread_cond_broadcast and
- * pthread_cond_signal to 'pulse' the condition variable.
- *
- * This means atomically decrementing the counter value
- * while leaving the other bits untouched.
- */
-static void
-__pthread_cond_pulse(pthread_cond_t *cond)
-{
-    long flags = (cond->value & ~COND_COUNTER_MASK);
-
-    for (;;) {
-        long  oldval  = cond->value;
-        long  newval  = ((oldval - COND_COUNTER_INCREMENT) & COND_COUNTER_MASK) | flags;
-        if (__atomic_cmpxchg(oldval, newval, &cond->value) == 0)
-            break;
-    }
-}
-
 int pthread_cond_broadcast(pthread_cond_t *cond)
 {
-    if (cond == NULL)
-        return EINVAL;
-
-    __pthread_cond_pulse(cond);
-
-    if (COND_IS_SHARED(cond)) {
-        __futex_wake(&cond->value, INT_MAX);
-    } else {
-        __futex_wake_private(&cond->value, INT_MAX);
-    }
-
+    __atomic_dec(&cond->value);
+    __futex_wake(&cond->value, INT_MAX);
     return 0;
 }
 
 int pthread_cond_signal(pthread_cond_t *cond)
 {
-    if (cond == NULL)
-        return EINVAL;
-
-    __pthread_cond_pulse(cond);
-
-    if (COND_IS_SHARED(cond)) {
-        __futex_wake(&cond->value, 1);
-    } else {
-        __futex_wake_private(&cond->value, 1);
-    }
+    __atomic_dec(&cond->value);
+    __futex_wake(&cond->value, 1);
     return 0;
 }
 
@@ -1493,11 +1302,7 @@ int __pthread_cond_timedwait_relative(pthread_cond_t *cond,
     int  oldvalue = cond->value;
 
     pthread_mutex_unlock(mutex);
-    if (COND_IS_SHARED(cond)) {
-        status = __futex_wait(&cond->value, oldvalue, reltime);
-    } else {
-        status = __futex_wait_private(&cond->value, oldvalue, reltime);
-    }
+    status = __futex_wait(&cond->value, oldvalue, reltime);
     pthread_mutex_lock(mutex);
 
     if (status == (-ETIMEDOUT)) return ETIMEDOUT;
diff --git a/libc/docs/CHANGES.TXT b/libc/docs/CHANGES.TXT
index 2e3ba62a0..4f875473d 100644
--- a/libc/docs/CHANGES.TXT
+++ b/libc/docs/CHANGES.TXT
@@ -80,16 +80,6 @@ Differences between current and Android 2.1:
   an unknown domain name. Due to an initialization bug, a random DNS search
   list was generated for each thread is net.dns.search is not defined.
 
-- <pthread.h>: Add pthread_condattr_init/destroy/setpshared/getpshared.
-  Also modify mutex and condvar implementation to use private futexes by
-  default, unless PROCESS_SHARED is specified in the init attributes.
-
-  Private futexes are limited to a single address space and can't be shared
-  among processes. However they are much faster to wake/wait for. This should
-  speed up mutex and condvar operations.
-
-  NOTE: PROCESS_SHARED mutexes are still NOT robust (see note below).
-
 -------------------------------------------------------------------------------
 Differences between Android 2.1 and 2.0.1:
 
diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 5c0a34937..6603b3f6c 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -165,11 +165,6 @@ int pthread_mutex_unlock(pthread_mutex_t *mutex);
 int pthread_mutex_trylock(pthread_mutex_t *mutex);
 int pthread_mutex_timedlock(pthread_mutex_t *mutex, struct timespec*  ts);
 
-int pthread_condattr_init(pthread_condattr_t *attr);
-int pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared);
-int pthread_condattr_getpshared(pthread_condattr_t *attr, int *pshared);
-int pthread_condattr_destroy(pthread_condattr_t *attr);
-
 int pthread_cond_init(pthread_cond_t *cond,
                       const pthread_condattr_t *attr);
 int pthread_cond_destroy(pthread_cond_t *cond);