<pthread.h> fixes and pthread cleanup.

<pthread.h> was missing nonnull attributes, noreturn on pthread_exit,
and had incorrect cv qualifiers for several standard functions.

I've also marked the non-standard stuff (where I count glibc rather
than POSIX as "standard") so we can revisit this cruft for LP64 and
try to ensure we're compatible with glibc.

I've also broken out the pthread_cond* functions into a new file.

I've made the remaining pthread files (plus ptrace) part of the bionic code
and fixed all the warnings.

I've added a few more smoke tests for chunks of untested pthread functionality.

We no longer need the libc_static_common_src_files hack for any of the
pthread implementation because we long since stripped out the rest of
the armv5 support, and this hack was just to ensure that __get_tls in libc.a
went via the kernel if necessary.

This patch also finishes the job of breaking up the pthread.c monolith, and
adds a handful of new tests.

Change-Id: Idc0ae7f5d8aa65989598acd4c01a874fe21582c7

1 files changed, 844 insertions, 0 deletions

diff --git a/libc/bionic/pthread_mutex.cpp b/libc/bionic/pthread_mutex.cpp
new file mode 100644
index 0000000..6b82151
--- /dev/null
+++ b/libc/bionic/pthread_mutex.cpp
@@ -0,0 +1,844 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <pthread.h>
+
+#include <errno.h>
+#include <limits.h>
+#include <sys/atomics.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "pthread_internal.h"
+
+#include "private/bionic_atomic_inline.h"
+#include "private/bionic_futex.h"
+#include "private/bionic_pthread.h"
+#include "private/bionic_tls.h"
+#include "private/thread_private.h"
+
+extern void pthread_debug_mutex_lock_check(pthread_mutex_t *mutex);
+extern void pthread_debug_mutex_unlock_check(pthread_mutex_t *mutex);
+
+/* a mutex is implemented as a 32-bit integer holding the following fields
+ *
+ * bits:     name     description
+ * 31-16     tid      owner thread's tid (recursive and errorcheck only)
+ * 15-14     type     mutex type
+ * 13        shared   process-shared flag
+ * 12-2      counter  counter of recursive mutexes
+ * 1-0       state    lock state (0, 1 or 2)
+ */
+
+/* Convenience macro, creates a mask of 'bits' bits that starts from
+ * the 'shift'-th least significant bit in a 32-bit word.
+ *
+ * Examples: FIELD_MASK(0,4)  -> 0xf
+ *           FIELD_MASK(16,9) -> 0x1ff0000
+ */
+#define  FIELD_MASK(shift,bits)           (((1 << (bits))-1) << (shift))
+
+/* This one is used to create a bit pattern from a given field value */
+#define  FIELD_TO_BITS(val,shift,bits)    (((val) & ((1 << (bits))-1)) << (shift))
+
+/* And this one does the opposite, i.e. extract a field's value from a bit pattern */
+#define  FIELD_FROM_BITS(val,shift,bits)  (((val) >> (shift)) & ((1 << (bits))-1))
+
+/* Mutex state:
+ *
+ * 0 for unlocked
+ * 1 for locked, no waiters
+ * 2 for locked, maybe waiters
+ */
+#define  MUTEX_STATE_SHIFT      0
+#define  MUTEX_STATE_LEN        2
+
+#define  MUTEX_STATE_MASK           FIELD_MASK(MUTEX_STATE_SHIFT, MUTEX_STATE_LEN)
+#define  MUTEX_STATE_FROM_BITS(v)   FIELD_FROM_BITS(v, MUTEX_STATE_SHIFT, MUTEX_STATE_LEN)
+#define  MUTEX_STATE_TO_BITS(v)     FIELD_TO_BITS(v, MUTEX_STATE_SHIFT, MUTEX_STATE_LEN)
+
+#define  MUTEX_STATE_UNLOCKED            0   /* must be 0 to match __PTHREAD_MUTEX_INIT_VALUE */
+#define  MUTEX_STATE_LOCKED_UNCONTENDED  1   /* must be 1 due to atomic dec in unlock operation */
+#define  MUTEX_STATE_LOCKED_CONTENDED    2   /* must be 1 + LOCKED_UNCONTENDED due to atomic dec */
+
+#define  MUTEX_STATE_FROM_BITS(v)    FIELD_FROM_BITS(v, MUTEX_STATE_SHIFT, MUTEX_STATE_LEN)
+#define  MUTEX_STATE_TO_BITS(v)      FIELD_TO_BITS(v, MUTEX_STATE_SHIFT, MUTEX_STATE_LEN)
+
+#define  MUTEX_STATE_BITS_UNLOCKED            MUTEX_STATE_TO_BITS(MUTEX_STATE_UNLOCKED)
+#define  MUTEX_STATE_BITS_LOCKED_UNCONTENDED  MUTEX_STATE_TO_BITS(MUTEX_STATE_LOCKED_UNCONTENDED)
+#define  MUTEX_STATE_BITS_LOCKED_CONTENDED    MUTEX_STATE_TO_BITS(MUTEX_STATE_LOCKED_CONTENDED)
+
+/* return true iff the mutex if locked with no waiters */
+#define  MUTEX_STATE_BITS_IS_LOCKED_UNCONTENDED(v)  (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_LOCKED_UNCONTENDED)
+
+/* return true iff the mutex if locked with maybe waiters */
+#define  MUTEX_STATE_BITS_IS_LOCKED_CONTENDED(v)   (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_LOCKED_CONTENDED)
+
+/* used to flip from LOCKED_UNCONTENDED to LOCKED_CONTENDED */
+#define  MUTEX_STATE_BITS_FLIP_CONTENTION(v)      ((v) ^ (MUTEX_STATE_BITS_LOCKED_CONTENDED ^ MUTEX_STATE_BITS_LOCKED_UNCONTENDED))
+
+/* Mutex counter:
+ *
+ * We need to check for overflow before incrementing, and we also need to
+ * detect when the counter is 0
+ */
+#define  MUTEX_COUNTER_SHIFT         2
+#define  MUTEX_COUNTER_LEN           11
+#define  MUTEX_COUNTER_MASK          FIELD_MASK(MUTEX_COUNTER_SHIFT, MUTEX_COUNTER_LEN)
+
+#define  MUTEX_COUNTER_BITS_WILL_OVERFLOW(v)    (((v) & MUTEX_COUNTER_MASK) == MUTEX_COUNTER_MASK)
+#define  MUTEX_COUNTER_BITS_IS_ZERO(v)          (((v) & MUTEX_COUNTER_MASK) == 0)
+
+/* Used to increment the counter directly after overflow has been checked */
+#define  MUTEX_COUNTER_BITS_ONE      FIELD_TO_BITS(1,MUTEX_COUNTER_SHIFT,MUTEX_COUNTER_LEN)
+
+/* Returns true iff the counter is 0 */
+#define  MUTEX_COUNTER_BITS_ARE_ZERO(v)  (((v) & MUTEX_COUNTER_MASK) == 0)
+
+/* Mutex shared bit flag
+ *
+ * This flag is set to indicate that the mutex is shared among processes.
+ * This changes the futex opcode we use for futex wait/wake operations
+ * (non-shared operations are much faster).
+ */
+#define  MUTEX_SHARED_SHIFT    13
+#define  MUTEX_SHARED_MASK     FIELD_MASK(MUTEX_SHARED_SHIFT,1)
+
+/* Mutex type:
+ *
+ * We support normal, recursive and errorcheck mutexes.
+ *
+ * The constants defined here *cannot* be changed because they must match
+ * the C library ABI which defines the following initialization values in
+ * <pthread.h>:
+ *
+ *   __PTHREAD_MUTEX_INIT_VALUE
+ *   __PTHREAD_RECURSIVE_MUTEX_VALUE
+ *   __PTHREAD_ERRORCHECK_MUTEX_INIT_VALUE
+ */
+#define  MUTEX_TYPE_SHIFT      14
+#define  MUTEX_TYPE_LEN        2
+#define  MUTEX_TYPE_MASK       FIELD_MASK(MUTEX_TYPE_SHIFT,MUTEX_TYPE_LEN)
+
+#define  MUTEX_TYPE_NORMAL          0  /* Must be 0 to match __PTHREAD_MUTEX_INIT_VALUE */
+#define  MUTEX_TYPE_RECURSIVE       1
+#define  MUTEX_TYPE_ERRORCHECK      2
+
+#define  MUTEX_TYPE_TO_BITS(t)       FIELD_TO_BITS(t, MUTEX_TYPE_SHIFT, MUTEX_TYPE_LEN)
+
+#define  MUTEX_TYPE_BITS_NORMAL      MUTEX_TYPE_TO_BITS(MUTEX_TYPE_NORMAL)
+#define  MUTEX_TYPE_BITS_RECURSIVE   MUTEX_TYPE_TO_BITS(MUTEX_TYPE_RECURSIVE)
+#define  MUTEX_TYPE_BITS_ERRORCHECK  MUTEX_TYPE_TO_BITS(MUTEX_TYPE_ERRORCHECK)
+
+/* Mutex owner field:
+ *
+ * This is only used for recursive and errorcheck mutexes. It holds the
+ * tid of the owning thread. Note that this works because the Linux
+ * kernel _only_ uses 16-bit values for tids.
+ *
+ * More specifically, it will wrap to 10000 when it reaches over 32768 for
+ * application processes. You can check this by running the following inside
+ * an adb shell session:
+ *
+    OLDPID=$$;
+    while true; do
+    NEWPID=$(sh -c 'echo $$')
+    if [ "$NEWPID" -gt 32768 ]; then
+        echo "AARGH: new PID $NEWPID is too high!"
+        exit 1
+    fi
+    if [ "$NEWPID" -lt "$OLDPID" ]; then
+        echo "****** Wrapping from PID $OLDPID to $NEWPID. *******"
+    else
+        echo -n "$NEWPID!"
+    fi
+    OLDPID=$NEWPID
+    done
+
+ * Note that you can run the same example on a desktop Linux system,
+ * the wrapping will also happen at 32768, but will go back to 300 instead.
+ */
+#define  MUTEX_OWNER_SHIFT     16
+#define  MUTEX_OWNER_LEN       16
+
+#define  MUTEX_OWNER_FROM_BITS(v)    FIELD_FROM_BITS(v,MUTEX_OWNER_SHIFT,MUTEX_OWNER_LEN)
+#define  MUTEX_OWNER_TO_BITS(v)      FIELD_TO_BITS(v,MUTEX_OWNER_SHIFT,MUTEX_OWNER_LEN)
+
+/* Convenience macros.
+ *
+ * These are used to form or modify the bit pattern of a given mutex value
+ */
+
+
+
+/* a mutex attribute holds the following fields
+ *
+ * bits:     name       description
+ * 0-3       type       type of mutex
+ * 4         shared     process-shared flag
+ */
+#define  MUTEXATTR_TYPE_MASK   0x000f
+#define  MUTEXATTR_SHARED_MASK 0x0010
+
+
+int pthread_mutexattr_init(pthread_mutexattr_t *attr)
+{
+    if (attr) {
+        *attr = PTHREAD_MUTEX_DEFAULT;
+        return 0;
+    } else {
+        return EINVAL;
+    }
+}
+
+int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
+{
+    if (attr) {
+        *attr = -1;
+        return 0;
+    } else {
+        return EINVAL;
+    }
+}
+
+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;
+        }
+    }
+    return EINVAL;
+}
+
+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;
+        return 0;
+    }
+    return EINVAL;
+}
+
+/* process-shared mutexes are not supported at the moment */
+
+int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int  pshared)
+{
+    if (!attr)
+        return EINVAL;
+
+    switch (pshared) {
+    case PTHREAD_PROCESS_PRIVATE:
+        *attr &= ~MUTEXATTR_SHARED_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_SHARED_MASK;
+        return 0;
+    }
+    return EINVAL;
+}
+
+int pthread_mutexattr_getpshared(const pthread_mutexattr_t* attr, int* pshared) {
+    if (!attr || !pshared)
+        return EINVAL;
+
+    *pshared = (*attr & MUTEXATTR_SHARED_MASK) ? PTHREAD_PROCESS_SHARED
+                                               : PTHREAD_PROCESS_PRIVATE;
+    return 0;
+}
+
+int pthread_mutex_init(pthread_mutex_t *mutex,
+                       const pthread_mutexattr_t *attr)
+{
+    int value = 0;
+
+    if (mutex == NULL)
+        return EINVAL;
+
+    if (__predict_true(attr == NULL)) {
+        mutex->value = MUTEX_TYPE_BITS_NORMAL;
+        return 0;
+    }
+
+    if ((*attr & MUTEXATTR_SHARED_MASK) != 0)
+        value |= MUTEX_SHARED_MASK;
+
+    switch (*attr & MUTEXATTR_TYPE_MASK) {
+    case PTHREAD_MUTEX_NORMAL:
+        value |= MUTEX_TYPE_BITS_NORMAL;
+        break;
+    case PTHREAD_MUTEX_RECURSIVE:
+        value |= MUTEX_TYPE_BITS_RECURSIVE;
+        break;
+    case PTHREAD_MUTEX_ERRORCHECK:
+        value |= MUTEX_TYPE_BITS_ERRORCHECK;
+        break;
+    default:
+        return EINVAL;
+    }
+
+    mutex->value = value;
+    return 0;
+}
+
+
+/*
+ * Lock a non-recursive mutex.
+ *
+ * As noted above, there are three states:
+ *   0 (unlocked, no contention)
+ *   1 (locked, no contention)
+ *   2 (locked, contention)
+ *
+ * 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.
+ */
+static __inline__ void
+_normal_lock(pthread_mutex_t*  mutex, int shared)
+{
+    /* convenience shortcuts */
+    const int unlocked           = shared | MUTEX_STATE_BITS_UNLOCKED;
+    const int locked_uncontended = shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
+    /*
+     * The common case is an unlocked mutex, so we begin by trying to
+     * change the lock's state from 0 (UNLOCKED) to 1 (LOCKED).
+     * __bionic_cmpxchg() returns 0 if it made the swap successfully.
+     * If the result is nonzero, this lock is already held by another thread.
+     */
+    if (__bionic_cmpxchg(unlocked, locked_uncontended, &mutex->value) != 0) {
+        const int locked_contended = shared | MUTEX_STATE_BITS_LOCKED_CONTENDED;
+        /*
+         * We want to go to sleep until the mutex is available, which
+         * requires promoting it to state 2 (CONTENDED). We need to
+         * swap in the new state value and then wait until somebody wakes us up.
+         *
+         * __bionic_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 (__bionic_swap(locked_contended, &mutex->value) != unlocked)
+            __futex_wait_ex(&mutex->value, shared, locked_contended, 0);
+    }
+    ANDROID_MEMBAR_FULL();
+}
+
+/*
+ * Release a non-recursive mutex.  The caller is responsible for determining
+ * that we are in fact the owner of this lock.
+ */
+static __inline__ void
+_normal_unlock(pthread_mutex_t*  mutex, int shared)
+{
+    ANDROID_MEMBAR_FULL();
+
+    /*
+     * The mutex state will be 1 or (rarely) 2.  We use an atomic decrement
+     * to release the lock.  __bionic_atomic_dec() returns the previous value;
+     * if it wasn't 1 we have to do some additional work.
+     */
+    if (__bionic_atomic_dec(&mutex->value) != (shared|MUTEX_STATE_BITS_LOCKED_UNCONTENDED)) {
+        /*
+         * 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 = shared;
+
+        /*
+         * 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_ex(&mutex->value, shared, 1);
+    }
+}
+
+/* This common inlined function is used to increment the counter of an
+ * errorcheck or recursive mutex.
+ *
+ * For errorcheck mutexes, it will return EDEADLK
+ * If the counter overflows, it will return EAGAIN
+ * Otherwise, it atomically increments the counter and returns 0
+ * after providing an acquire barrier.
+ *
+ * mtype is the current mutex type
+ * mvalue is the current mutex value (already loaded)
+ * mutex pointers to the mutex.
+ */
+static __inline__ __attribute__((always_inline)) int
+_recursive_increment(pthread_mutex_t* mutex, int mvalue, int mtype)
+{
+    if (mtype == MUTEX_TYPE_BITS_ERRORCHECK) {
+        /* trying to re-lock a mutex we already acquired */
+        return EDEADLK;
+    }
+
+    /* Detect recursive lock overflow and return EAGAIN.
+     * This is safe because only the owner thread can modify the
+     * counter bits in the mutex value.
+     */
+    if (MUTEX_COUNTER_BITS_WILL_OVERFLOW(mvalue)) {
+        return EAGAIN;
+    }
+
+    /* We own the mutex, but other threads are able to change
+     * the lower bits (e.g. promoting it to "contended"), so we
+     * need to use an atomic cmpxchg loop to update the counter.
+     */
+    for (;;) {
+        /* increment counter, overflow was already checked */
+        int newval = mvalue + MUTEX_COUNTER_BITS_ONE;
+        if (__predict_true(__bionic_cmpxchg(mvalue, newval, &mutex->value) == 0)) {
+            /* mutex is still locked, not need for a memory barrier */
+            return 0;
+        }
+        /* the value was changed, this happens when another thread changes
+         * the lower state bits from 1 to 2 to indicate contention. This
+         * cannot change the counter, so simply reload and try again.
+         */
+        mvalue = mutex->value;
+    }
+}
+
+__LIBC_HIDDEN__
+int pthread_mutex_lock_impl(pthread_mutex_t *mutex)
+{
+    int mvalue, mtype, tid, shared;
+
+    if (__predict_false(mutex == NULL))
+        return EINVAL;
+
+    mvalue = mutex->value;
+    mtype = (mvalue & MUTEX_TYPE_MASK);
+    shared = (mvalue & MUTEX_SHARED_MASK);
+
+    /* Handle normal case first */
+    if ( __predict_true(mtype == MUTEX_TYPE_BITS_NORMAL) ) {
+        _normal_lock(mutex, shared);
+        return 0;
+    }
+
+    /* Do we already own this recursive or error-check mutex ? */
+    tid = __get_thread()->tid;
+    if ( tid == MUTEX_OWNER_FROM_BITS(mvalue) )
+        return _recursive_increment(mutex, mvalue, mtype);
+
+    /* Add in shared state to avoid extra 'or' operations below */
+    mtype |= shared;
+
+    /* First, if the mutex is unlocked, try to quickly acquire it.
+     * In the optimistic case where this works, set the state to 1 to
+     * indicate locked with no contention */
+    if (mvalue == mtype) {
+        int newval = MUTEX_OWNER_TO_BITS(tid) | mtype | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
+        if (__bionic_cmpxchg(mvalue, newval, &mutex->value) == 0) {
+            ANDROID_MEMBAR_FULL();
+            return 0;
+        }
+        /* argh, the value changed, reload before entering the loop */
+        mvalue = mutex->value;
+    }
+
+    for (;;) {
+        int newval;
+
+        /* if the mutex is unlocked, its value should be 'mtype' and
+         * we try to acquire it by setting its owner and state atomically.
+         * NOTE: We put the state to 2 since we _know_ there is contention
+         * when we are in this loop. This ensures all waiters will be
+         * unlocked.
+         */
+        if (mvalue == mtype) {
+            newval = MUTEX_OWNER_TO_BITS(tid) | mtype | MUTEX_STATE_BITS_LOCKED_CONTENDED;
+            /* TODO: Change this to __bionic_cmpxchg_acquire when we
+             *        implement it to get rid of the explicit memory
+             *        barrier below.
+             */
+            if (__predict_false(__bionic_cmpxchg(mvalue, newval, &mutex->value) != 0)) {
+                mvalue = mutex->value;
+                continue;
+            }
+            ANDROID_MEMBAR_FULL();
+            return 0;
+        }
+
+        /* the mutex is already locked by another thread, if its state is 1
+         * we will change it to 2 to indicate contention. */
+        if (MUTEX_STATE_BITS_IS_LOCKED_UNCONTENDED(mvalue)) {
+            newval = MUTEX_STATE_BITS_FLIP_CONTENTION(mvalue); /* locked state 1 => state 2 */
+            if (__predict_false(__bionic_cmpxchg(mvalue, newval, &mutex->value) != 0)) {
+                mvalue = mutex->value;
+                continue;
+            }
+            mvalue = newval;
+        }
+
+        /* wait until the mutex is unlocked */
+        __futex_wait_ex(&mutex->value, shared, mvalue, NULL);
+
+        mvalue = mutex->value;
+    }
+    /* NOTREACHED */
+}
+
+int pthread_mutex_lock(pthread_mutex_t *mutex)
+{
+    int err = pthread_mutex_lock_impl(mutex);
+#ifdef PTHREAD_DEBUG
+    if (PTHREAD_DEBUG_ENABLED) {
+        if (!err) {
+            pthread_debug_mutex_lock_check(mutex);
+        }
+    }
+#endif
+    return err;
+}
+
+__LIBC_HIDDEN__
+int pthread_mutex_unlock_impl(pthread_mutex_t *mutex)
+{
+    int mvalue, mtype, tid, shared;
+
+    if (__predict_false(mutex == NULL))
+        return EINVAL;
+
+    mvalue = mutex->value;
+    mtype  = (mvalue & MUTEX_TYPE_MASK);
+    shared = (mvalue & MUTEX_SHARED_MASK);
+
+    /* Handle common case first */
+    if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) {
+        _normal_unlock(mutex, shared);
+        return 0;
+    }
+
+    /* Do we already own this recursive or error-check mutex ? */
+    tid = __get_thread()->tid;
+    if ( tid != MUTEX_OWNER_FROM_BITS(mvalue) )
+        return EPERM;
+
+    /* If the counter is > 0, we can simply decrement it atomically.
+     * Since other threads can mutate the lower state bits (and only the
+     * lower state bits), use a cmpxchg to do it.
+     */
+    if (!MUTEX_COUNTER_BITS_IS_ZERO(mvalue)) {
+        for (;;) {
+            int newval = mvalue - MUTEX_COUNTER_BITS_ONE;
+            if (__predict_true(__bionic_cmpxchg(mvalue, newval, &mutex->value) == 0)) {
+                /* success: we still own the mutex, so no memory barrier */
+                return 0;
+            }
+            /* the value changed, so reload and loop */
+            mvalue = mutex->value;
+        }
+    }
+
+    /* the counter is 0, so we're going to unlock the mutex by resetting
+     * its value to 'unlocked'. We need to perform a swap in order
+     * to read the current state, which will be 2 if there are waiters
+     * to awake.
+     *
+     * TODO: Change this to __bionic_swap_release when we implement it
+     *        to get rid of the explicit memory barrier below.
+     */
+    ANDROID_MEMBAR_FULL();  /* RELEASE BARRIER */
+    mvalue = __bionic_swap(mtype | shared | MUTEX_STATE_BITS_UNLOCKED, &mutex->value);
+
+    /* Wake one waiting thread, if any */
+    if (MUTEX_STATE_BITS_IS_LOCKED_CONTENDED(mvalue)) {
+        __futex_wake_ex(&mutex->value, shared, 1);
+    }
+    return 0;
+}
+
+int pthread_mutex_unlock(pthread_mutex_t *mutex)
+{
+#ifdef PTHREAD_DEBUG
+    if (PTHREAD_DEBUG_ENABLED) {
+        pthread_debug_mutex_unlock_check(mutex);
+    }
+#endif
+    return pthread_mutex_unlock_impl(mutex);
+}
+
+__LIBC_HIDDEN__
+int pthread_mutex_trylock_impl(pthread_mutex_t *mutex)
+{
+    int mvalue, mtype, tid, shared;
+
+    if (__predict_false(mutex == NULL))
+        return EINVAL;
+
+    mvalue = mutex->value;
+    mtype  = (mvalue & MUTEX_TYPE_MASK);
+    shared = (mvalue & MUTEX_SHARED_MASK);
+
+    /* Handle common case first */
+    if ( __predict_true(mtype == MUTEX_TYPE_BITS_NORMAL) )
+    {
+        if (__bionic_cmpxchg(shared|MUTEX_STATE_BITS_UNLOCKED,
+                             shared|MUTEX_STATE_BITS_LOCKED_UNCONTENDED,
+                             &mutex->value) == 0) {
+            ANDROID_MEMBAR_FULL();
+            return 0;
+        }
+
+        return EBUSY;
+    }
+
+    /* Do we already own this recursive or error-check mutex ? */
+    tid = __get_thread()->tid;
+    if ( tid == MUTEX_OWNER_FROM_BITS(mvalue) )
+        return _recursive_increment(mutex, mvalue, mtype);
+
+    /* Same as pthread_mutex_lock, except that we don't want to wait, and
+     * the only operation that can succeed is a single cmpxchg to acquire the
+     * lock if it is released / not owned by anyone. No need for a complex loop.
+     */
+    mtype |= shared | MUTEX_STATE_BITS_UNLOCKED;
+    mvalue = MUTEX_OWNER_TO_BITS(tid) | mtype | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
+
+    if (__predict_true(__bionic_cmpxchg(mtype, mvalue, &mutex->value) == 0)) {
+        ANDROID_MEMBAR_FULL();
+        return 0;
+    }
+
+    return EBUSY;
+}
+
+int pthread_mutex_trylock(pthread_mutex_t *mutex)
+{
+    int err = pthread_mutex_trylock_impl(mutex);
+#ifdef PTHREAD_DEBUG
+    if (PTHREAD_DEBUG_ENABLED) {
+        if (!err) {
+            pthread_debug_mutex_lock_check(mutex);
+        }
+    }
+#endif
+    return err;
+}
+
+/* initialize 'abstime' to the current time according to 'clock' plus 'msecs'
+ * milliseconds.
+ */
+static void __timespec_to_relative_msec(timespec* abstime, unsigned msecs, clockid_t clock) {
+    clock_gettime(clock, abstime);
+    abstime->tv_sec  += msecs/1000;
+    abstime->tv_nsec += (msecs%1000)*1000000;
+    if (abstime->tv_nsec >= 1000000000) {
+        abstime->tv_sec++;
+        abstime->tv_nsec -= 1000000000;
+    }
+}
+
+__LIBC_HIDDEN__
+int pthread_mutex_lock_timeout_np_impl(pthread_mutex_t *mutex, unsigned msecs)
+{
+    clockid_t        clock = CLOCK_MONOTONIC;
+    timespec  abstime;
+    timespec  ts;
+    int               mvalue, mtype, tid, shared;
+
+    /* compute absolute expiration time */
+    __timespec_to_relative_msec(&abstime, msecs, clock);
+
+    if (__predict_false(mutex == NULL))
+        return EINVAL;
+
+    mvalue = mutex->value;
+    mtype  = (mvalue & MUTEX_TYPE_MASK);
+    shared = (mvalue & MUTEX_SHARED_MASK);
+
+    /* Handle common case first */
+    if ( __predict_true(mtype == MUTEX_TYPE_BITS_NORMAL) )
+    {
+        const int unlocked           = shared | MUTEX_STATE_BITS_UNLOCKED;
+        const int locked_uncontended = shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
+        const int locked_contended   = shared | MUTEX_STATE_BITS_LOCKED_CONTENDED;
+
+        /* fast path for uncontended lock. Note: MUTEX_TYPE_BITS_NORMAL is 0 */
+        if (__bionic_cmpxchg(unlocked, locked_uncontended, &mutex->value) == 0) {
+            ANDROID_MEMBAR_FULL();
+            return 0;
+        }
+
+        /* loop while needed */
+        while (__bionic_swap(locked_contended, &mutex->value) != unlocked) {
+            if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
+                return EBUSY;
+
+            __futex_wait_ex(&mutex->value, shared, locked_contended, &ts);
+        }
+        ANDROID_MEMBAR_FULL();
+        return 0;
+    }
+
+    /* Do we already own this recursive or error-check mutex ? */
+    tid = __get_thread()->tid;
+    if ( tid == MUTEX_OWNER_FROM_BITS(mvalue) )
+        return _recursive_increment(mutex, mvalue, mtype);
+
+    /* the following implements the same loop than pthread_mutex_lock_impl
+     * but adds checks to ensure that the operation never exceeds the
+     * absolute expiration time.
+     */
+    mtype |= shared;
+
+    /* first try a quick lock */
+    if (mvalue == mtype) {
+        mvalue = MUTEX_OWNER_TO_BITS(tid) | mtype | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
+        if (__predict_true(__bionic_cmpxchg(mtype, mvalue, &mutex->value) == 0)) {
+            ANDROID_MEMBAR_FULL();
+            return 0;
+        }
+        mvalue = mutex->value;
+    }
+
+    for (;;) {
+        timespec ts;
+
+        /* if the value is 'unlocked', try to acquire it directly */
+        /* NOTE: put state to 2 since we know there is contention */
+        if (mvalue == mtype) /* unlocked */ {
+            mvalue = MUTEX_OWNER_TO_BITS(tid) | mtype | MUTEX_STATE_BITS_LOCKED_CONTENDED;
+            if (__bionic_cmpxchg(mtype, mvalue, &mutex->value) == 0) {
+                ANDROID_MEMBAR_FULL();
+                return 0;
+            }
+            /* the value changed before we could lock it. We need to check
+             * the time to avoid livelocks, reload the value, then loop again. */
+            if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
+                return EBUSY;
+
+            mvalue = mutex->value;
+            continue;
+        }
+
+        /* The value is locked. If 'uncontended', try to switch its state
+         * to 'contented' to ensure we get woken up later. */
+        if (MUTEX_STATE_BITS_IS_LOCKED_UNCONTENDED(mvalue)) {
+            int newval = MUTEX_STATE_BITS_FLIP_CONTENTION(mvalue);
+            if (__bionic_cmpxchg(mvalue, newval, &mutex->value) != 0) {
+                /* this failed because the value changed, reload it */
+                mvalue = mutex->value;
+            } else {
+                /* this succeeded, update mvalue */
+                mvalue = newval;
+            }
+        }
+
+        /* check time and update 'ts' */
+        if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
+            return EBUSY;
+
+        /* Only wait to be woken up if the state is '2', otherwise we'll
+         * simply loop right now. This can happen when the second cmpxchg
+         * in our loop failed because the mutex was unlocked by another
+         * thread.
+         */
+        if (MUTEX_STATE_BITS_IS_LOCKED_CONTENDED(mvalue)) {
+            if (__futex_wait_ex(&mutex->value, shared, mvalue, &ts) == ETIMEDOUT) {
+                return EBUSY;
+            }
+            mvalue = mutex->value;
+        }
+    }
+    /* NOTREACHED */
+}
+
+int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
+{
+    int err = pthread_mutex_lock_timeout_np_impl(mutex, msecs);
+#ifdef PTHREAD_DEBUG
+    if (PTHREAD_DEBUG_ENABLED) {
+        if (!err) {
+            pthread_debug_mutex_lock_check(mutex);
+        }
+    }
+#endif
+    return err;
+}
+
+int pthread_mutex_destroy(pthread_mutex_t *mutex)
+{
+    int ret;
+
+    /* use trylock to ensure that the mutex value is
+     * valid and is not already locked. */
+    ret = pthread_mutex_trylock_impl(mutex);
+    if (ret != 0)
+        return ret;
+
+    mutex->value = 0xdead10cc;
+    return 0;
+}