From: David 'Digit' Turner Date: Fri, 19 Mar 2010 00:13:41 +0000 (-0700) Subject: Use private futexes for pthread_mutex_t. X-Git-Tag: android-x86-2.2~59 X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=88f06cd84a70f8a5212cb03272ec2c7cf0017afa;p=android-x86%2Fbionic.git Use private futexes for pthread_mutex_t. This does not change the implementation of conditional variables since we're waiting for other system components to properly use pthread_condattr_init/setpshared before that. Also remove an obsolete x86 source file. Change-Id: Ia3e3fbac35b87a534fb04d4381c3c66b975bc8f7 --- diff --git a/libc/arch-arm/bionic/atomics_arm.S b/libc/arch-arm/bionic/atomics_arm.S index 55c642f8d..047541fc2 100644 --- a/libc/arch-arm/bionic/atomics_arm.S +++ b/libc/arch-arm/bionic/atomics_arm.S @@ -35,10 +35,6 @@ .type __atomic_dec, %function .global __atomic_inc .type __atomic_inc, %function -.global __futex_wait -.type __futex_wait, %function -.global __futex_wake -.type __futex_wake, %function #define FUTEX_WAIT 0 #define FUTEX_WAKE 1 @@ -159,10 +155,34 @@ __atomic_swap: bx lr /* __futex_wait(*ftx, val, *timespec) */ -/* __futex_syscall(*ftx, op, val, *timespec, *addr2, val3) */ +/* __futex_wake(*ftx, counter) */ +/* __futex_syscall3(*ftx, op, val) */ +/* __futex_syscall4(*ftx, op, val, *timespec) */ + +.global __futex_wait +.type __futex_wait, %function + +.global __futex_wake +.type __futex_wake, %function + +.global __futex_syscall3 +.type __futex_syscall3, %function + +.global __futex_syscall4 +.type __futex_syscall4, %function #if __ARM_EABI__ +__futex_syscall3: + .fnstart + stmdb sp!, {r4, r7} + .save {r4, r7} + ldr r7, =__NR_futex + swi #0 + ldmia sp!, {r4, r7} + bx lr + .fnend + __futex_wait: .fnstart stmdb sp!, {r4, r7} @@ -187,6 +207,10 @@ __futex_wake: #else +__futex_syscall3: + swi #__NR_futex + bx lr + __futex_wait: mov r3, r2 mov r2, r1 @@ -201,3 +225,6 @@ __futex_wake: bx lr #endif + +__futex_syscall4: + b __futex_syscall3 diff --git a/libc/arch-sh/bionic/atomics_sh.c b/libc/arch-sh/bionic/atomics_sh.c index 16966f762..c7815ff2c 100644 --- a/libc/arch-sh/bionic/atomics_sh.c +++ b/libc/arch-sh/bionic/atomics_sh.c @@ -98,3 +98,13 @@ int __futex_wake(volatile void *ftx, int count) { return futex(ftx, FUTEX_WAKE, count, NULL, NULL, 0); } + +int __futex_syscall3(volatile void *ftx, int op, int val) +{ + return futex(ftx, op, val, NULL, NULL, 0); +} + +int __futex_syscall4(volative void *ftx, int op, int val, const struct timespec *timeout) +{ + return futex(ftx, op, val, (void *)timeout, NULL, 0); +} diff --git a/libc/arch-x86/bionic/atomics_x86.S b/libc/arch-x86/bionic/atomics_x86.S index 2370f2358..666e1821c 100644 --- a/libc/arch-x86/bionic/atomics_x86.S +++ b/libc/arch-x86/bionic/atomics_x86.S @@ -41,6 +41,38 @@ __futex_wake: popl %ebx ret +/* int __futex_syscall3(volatile void *ftx, int op, int count) */ +.text +.globl __futex_syscall3 +.type __futex_syscall3, @function +.align 4 +__futex_syscall3: + pushl %ebx + movl 8(%esp), %ebx /* ftx */ + movl 12(%esp), %ecx /* op */ + movl 16(%esp), %edx /* value */ + movl $__NR_futex, %eax + int $0x80 + popl %ebx + ret + +/* int __futex_syscall4(volatile void *ftx, int op, int val, const struct timespec *timeout) */ +.text +.globl __futex_syscall4 +.type __futex_syscall4, @function +.align 4 +__futex_syscall4: + pushl %ebx + pushl %esi + movl 12(%esp), %ebx /* ftx */ + movl 16(%esp), %ecx /* op */ + movl 20(%esp), %edx /* val */ + movl 24(%esp), %esi /* timeout */ + movl $__NR_futex, %eax + int $0x80 + popl %esi + popl %ebx + ret /* int __atomic_cmpxchg(int old, int new, volatile int* addr) */ diff --git a/libc/arch-x86/bionic/atomics_x86.c b/libc/arch-x86/bionic/atomics_x86.c deleted file mode 100644 index b7b20e6ef..000000000 --- a/libc/arch-x86/bionic/atomics_x86.c +++ /dev/null @@ -1,104 +0,0 @@ -/* - * 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 - -#define FUTEX_SYSCALL 240 -#define FUTEX_WAIT 0 -#define FUTEX_WAKE 1 - -int __futex_wait(volatile void *ftx, int val) -{ - int ret; - asm volatile ( - "int $0x80;" - : "=a" (ret) - : "0" (FUTEX_SYSCALL), - "b" (ftx), - "c" (FUTEX_WAIT), - "d" (val), - "S" (0) - ); - return ret; -} - -int __futex_wake(volatile void *ftx, int count) -{ - int ret; - asm volatile ( - "int $0x80;" - : "=a" (ret) - : "0" (FUTEX_SYSCALL), - "b" (ftx), - "c" (FUTEX_WAKE), - "d" (count) - ); - return ret; -} - -int __atomic_cmpxchg(int old, int new, volatile int* addr) { - int xchg; - asm volatile ( - "lock;" - "cmpxchg %%ecx, (%%edx);" - "setne %%al;" - : "=a" (xchg) - : "a" (old), - "c" (new), - "d" (addr) - ); - return xchg; -} - -int __atomic_swap(int new, volatile int* addr) { - int old; - asm volatile ( - "lock;" - "xchg %%ecx, (%%edx);" - : "=c" (old) - : "c" (new), - "d" (addr) - ); - return old; -} - -int __atomic_dec(volatile int* addr) { - int old; - do { - old = *addr; - } while (atomic_cmpxchg(old, old-1, addr)); - return old; -} - -int __atomic_inc(volatile int* addr) { - int old; - do { - old = *addr; - } while (atomic_cmpxchg(old, old+1, addr)); - return old; -} - diff --git a/libc/bionic/pthread.c b/libc/bionic/pthread.c index 4ffa9b8e3..3294ceafe 100644 --- a/libc/bionic/pthread.c +++ b/libc/bionic/pthread.c @@ -43,12 +43,16 @@ #include #include #include +#include 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); extern int __set_errno(int); +#define __likely(cond) __builtin_expect(!!(cond), 1) +#define __unlikely(cond) __builtin_expect(!!(cond), 0) + void _thread_created_hook(pid_t thread_id) __attribute__((noinline)); #define PTHREAD_ATTR_FLAG_DETACHED 0x00000001 @@ -712,6 +716,21 @@ 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_syscall3(volatile void *ftx, int op, int val); +int __futex_syscall4(volatile void *ftx, int op, int val, const struct timespec *timeout); + +#ifndef FUTEX_PRIVATE_FLAG +#define FUTEX_PRIVATE_FLAG 128 +#endif + +#ifndef FUTEX_WAIT_PRIVATE +#define FUTEX_WAIT_PRIVATE (FUTEX_WAIT|FUTEX_PRIVATE_FLAG) +#endif + +#ifndef FUTEX_WAKE_PRIVATE +#define FUTEX_WAKE_PRIVATE (FUTEX_WAKE|FUTEX_PRIVATE_FLAG) +#endif + // mutex lock states // // 0: unlocked @@ -723,7 +742,8 @@ int __futex_wake(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 - * 13-2 counter counter of recursive mutexes + * 13 shared process-shared flag + * 12-2 counter counter of recursive mutexes * 1-0 state lock state (0, 1 or 2) */ @@ -737,9 +757,17 @@ int __futex_wake(volatile void *ftx, int count); #define MUTEX_TYPE_ERRORCHECK 0x8000 #define MUTEX_COUNTER_SHIFT 2 -#define MUTEX_COUNTER_MASK 0x3ffc - +#define MUTEX_COUNTER_MASK 0x1ffc +#define MUTEX_SHARED_MASK 0x2000 +/* 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) @@ -764,10 +792,14 @@ int pthread_mutexattr_destroy(pthread_mutexattr_t *attr) int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type) { - if (attr && *attr >= PTHREAD_MUTEX_NORMAL && - *attr <= PTHREAD_MUTEX_ERRORCHECK ) { - *type = *attr; - return 0; + if (attr) { + int atype = (*attr & MUTEXATTR_TYPE_MASK); + + if (atype >= PTHREAD_MUTEX_NORMAL && + atype <= PTHREAD_MUTEX_ERRORCHECK) { + *type = atype; + return 0; + } } return EINVAL; } @@ -776,7 +808,7 @@ int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type) { if (attr && type >= PTHREAD_MUTEX_NORMAL && type <= PTHREAD_MUTEX_ERRORCHECK ) { - *attr = type; + *attr = (*attr & ~MUTEXATTR_TYPE_MASK) | type; return 0; } return EINVAL; @@ -791,54 +823,70 @@ int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared) 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 ENOTSUP; + return EINVAL; } int pthread_mutexattr_getpshared(pthread_mutexattr_t *attr, int *pshared) { - if (!attr) + if (!attr || !pshared) return EINVAL; - *pshared = PTHREAD_PROCESS_PRIVATE; + *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) { - 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; + int value = 0; - case PTHREAD_MUTEX_RECURSIVE: - mutex->value = MUTEX_TYPE_RECURSIVE; - return 0; + if (mutex == NULL) + return EINVAL; - case PTHREAD_MUTEX_ERRORCHECK: - mutex->value = MUTEX_TYPE_ERRORCHECK; - return 0; - } + if (__likely(attr == NULL)) { + mutex->value = MUTEX_TYPE_NORMAL; + return 0; } - return EINVAL; + + if ((*attr & MUTEXATTR_SHARED_MASK) != 0) + value |= MUTEX_SHARED_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; + } + + mutex->value = value; + return 0; } int pthread_mutex_destroy(pthread_mutex_t *mutex) { + if (__unlikely(mutex == NULL)) + return EINVAL; + mutex->value = 0xdead10cc; return 0; } @@ -859,13 +907,15 @@ int pthread_mutex_destroy(pthread_mutex_t *mutex) static __inline__ void _normal_lock(pthread_mutex_t* mutex) { + /* We need to preserve the shared flag during operations */ + int shared = mutex->value & MUTEX_SHARED_MASK; /* * 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) { + if (__atomic_cmpxchg(shared|0, shared|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 @@ -882,8 +932,10 @@ _normal_lock(pthread_mutex_t* mutex) * 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); + int wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE; + + while (__atomic_swap(shared|2, &mutex->value ) != (shared|0)) + __futex_syscall4(&mutex->value, wait_op, shared|2, 0); } } @@ -894,12 +946,16 @@ _normal_lock(pthread_mutex_t* mutex) static __inline__ void _normal_unlock(pthread_mutex_t* mutex) { + /* We need to preserve the shared flag during operations */ + int shared = mutex->value & MUTEX_SHARED_MASK; + /* - * The mutex value will be 1 or (rarely) 2. We use an atomic decrement + * The mutex state 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) { + if (__atomic_dec(&mutex->value) != (shared|1)) { + int wake_op = shared ? FUTEX_WAKE : FUTEX_WAKE_PRIVATE; /* * Start by releasing the lock. The decrement changed it from * "contended lock" to "uncontended lock", which means we still @@ -914,7 +970,7 @@ _normal_unlock(pthread_mutex_t* mutex) * _normal_lock(), because the __futex_wait() call there will * return immediately if the mutex value isn't 2. */ - mutex->value = 0; + mutex->value = shared; /* * Wake up one waiting thread. We don't know which thread will be @@ -937,7 +993,7 @@ _normal_unlock(pthread_mutex_t* mutex) * Either way we have correct behavior and nobody is orphaned on * the wait queue. */ - __futex_wake(&mutex->value, 1); + __futex_syscall3(&mutex->value, wake_op, 1); } } @@ -946,26 +1002,24 @@ static pthread_mutex_t __recursive_lock = PTHREAD_MUTEX_INITIALIZER; static void _recursive_lock(void) { - _normal_lock( &__recursive_lock); + _normal_lock(&__recursive_lock); } static void _recursive_unlock(void) { - _normal_unlock( &__recursive_lock ); + _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; + int mtype, tid, new_lock_type, shared, wait_op; if (__unlikely(mutex == NULL)) return EINVAL; mtype = (mutex->value & MUTEX_TYPE_MASK); + shared = (mutex->value & MUTEX_SHARED_MASK); /* Handle normal case first */ if ( __likely(mtype == MUTEX_TYPE_NORMAL) ) { @@ -1003,6 +1057,10 @@ int pthread_mutex_lock(pthread_mutex_t *mutex) */ new_lock_type = 1; + /* compute futex wait opcode and restore shared flag in mtype */ + wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE; + mtype |= shared; + for (;;) { int oldv; @@ -1027,7 +1085,7 @@ int pthread_mutex_lock(pthread_mutex_t *mutex) */ new_lock_type = 2; - __futex_wait( &mutex->value, oldv, 0 ); + __futex_syscall4(&mutex->value, wait_op, oldv, NULL); } return 0; } @@ -1035,12 +1093,13 @@ int pthread_mutex_lock(pthread_mutex_t *mutex) int pthread_mutex_unlock(pthread_mutex_t *mutex) { - int mtype, tid, oldv; + int mtype, tid, oldv, shared; if (__unlikely(mutex == NULL)) return EINVAL; - mtype = (mutex->value & MUTEX_TYPE_MASK); + mtype = (mutex->value & MUTEX_TYPE_MASK); + shared = (mutex->value & MUTEX_SHARED_MASK); /* Handle common case first */ if (__likely(mtype == MUTEX_TYPE_NORMAL)) { @@ -1060,31 +1119,33 @@ int pthread_mutex_unlock(pthread_mutex_t *mutex) mutex->value = oldv - (1 << MUTEX_COUNTER_SHIFT); oldv = 0; } else { - mutex->value = mtype; + mutex->value = shared | mtype; } _recursive_unlock(); /* Wake one waiting thread, if any */ - if ((oldv & 3) == 2) - __futex_wake( &mutex->value, 1 ); - + if ((oldv & 3) == 2) { + int wake_op = shared ? FUTEX_WAIT_PRIVATE : FUTEX_WAIT; + __futex_syscall3(&mutex->value, wake_op, 1); + } return 0; } int pthread_mutex_trylock(pthread_mutex_t *mutex) { - int mtype, tid, oldv; + int mtype, tid, oldv, shared; if (__unlikely(mutex == NULL)) return EINVAL; - mtype = (mutex->value & MUTEX_TYPE_MASK); + mtype = (mutex->value & MUTEX_TYPE_MASK); + shared = (mutex->value & MUTEX_SHARED_MASK); /* Handle common case first */ if ( __likely(mtype == MUTEX_TYPE_NORMAL) ) { - if (__atomic_cmpxchg(0, 1, &mutex->value) == 0) + if (__atomic_cmpxchg(shared|0, shared|1, &mutex->value) == 0) return 0; return EBUSY; @@ -1109,6 +1170,9 @@ int pthread_mutex_trylock(pthread_mutex_t *mutex) return 0; } + /* Restore sharing bit in mtype */ + mtype |= shared; + /* Try to lock it, just once. */ _recursive_lock(); oldv = mutex->value; @@ -1162,7 +1226,7 @@ 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, new_lock_type; + int mtype, tid, oldv, new_lock_type, shared, wait_op; /* compute absolute expiration time */ __timespec_to_relative_msec(&abstime, msecs, clock); @@ -1170,21 +1234,24 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs) if (__unlikely(mutex == NULL)) return EINVAL; - mtype = (mutex->value & MUTEX_TYPE_MASK); + mtype = (mutex->value & MUTEX_TYPE_MASK); + shared = (mutex->value & MUTEX_SHARED_MASK); /* Handle common case first */ if ( __likely(mtype == MUTEX_TYPE_NORMAL) ) { + int wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE; + /* fast path for unconteded lock */ - if (__atomic_cmpxchg(0, 1, &mutex->value) == 0) + if (__atomic_cmpxchg(shared|0, shared|1, &mutex->value) == 0) return 0; /* loop while needed */ - while (__atomic_swap(2, &mutex->value) != 0) { + while (__atomic_swap(shared|2, &mutex->value) != (shared|0)) { if (__timespec_to_absolute(&ts, &abstime, clock) < 0) return EBUSY; - __futex_wait(&mutex->value, 2, &ts); + __futex_syscall4(&mutex->value, wait_op, shared|2, &ts); } return 0; } @@ -1215,6 +1282,10 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs) */ new_lock_type = 1; + /* Compute wait op and restore sharing bit in mtype */ + wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE; + mtype |= shared; + for (;;) { int oldv; struct timespec ts; @@ -1243,7 +1314,7 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs) if (__timespec_to_absolute(&ts, &abstime, clock) < 0) return EBUSY; - __futex_wait( &mutex->value, oldv, &ts ); + __futex_syscall4(&mutex->value, wait_op, oldv, &ts); } return 0; } diff --git a/libc/docs/CHANGES.TXT b/libc/docs/CHANGES.TXT index ec147c26b..08b2009b3 100644 --- a/libc/docs/CHANGES.TXT +++ b/libc/docs/CHANGES.TXT @@ -83,6 +83,11 @@ Differences between current and Android 2.1: - : Add pthread_condattr_init/destroy/setpshared/getpshared functions to enable proper shared conditional variable initialization. + Modify the pthread_mutex_t implementation to use private futexes for + performance reasons. Mutexes are no longer shareable between processes + by default anymore, unless you use PTHREAD_PROCESS_SHARED with + pthread_mutexattr_setpshared(). + XXX: The implementation still always uses shared condvars, independent of the flags being selected. This will change in a later commit.