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Atomic/SMP update, part 3.

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Update ARM atomic ops to use LDREX/STREX.  Stripped out #if 0 chunk.

Insert explicit memory barriers in pthread and semaphore code.

For bug 2721865.

Change-Id: I0f153b797753a655702d8be41679273d1d5d6ae7
This commit is contained in:
Andy McFadden 2010-05-28 13:31:45 -07:00
parent 4fdbadde92
commit fcd00ebbdf
4 changed files with 109 additions and 61 deletions
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8
libc/Android.mk
View file

@ -455,6 +455,14 @@ else # !arm
endif # x86
endif # !arm
# Define ANDROID_SMP appropriately.
ifeq ($(TARGET_CPU_SMP),true)
libc_common_cflags += -DANDROID_SMP=1
else
libc_common_cflags += -DANDROID_SMP=0
endif
# Define some common includes
# ========================================================
libc_common_c_includes := \

133
libc/arch-arm/bionic/atomics_arm.S
View file

@ -26,6 +26,7 @@
* SUCH DAMAGE.
*/
#include <sys/linux-syscalls.h>
#include <machine/cpu-features.h>
.global __atomic_cmpxchg
.type __atomic_cmpxchg, %function
@ -39,9 +40,73 @@
#define FUTEX_WAIT 0
#define FUTEX_WAKE 1
#if 1
.equ kernel_cmpxchg, 0xFFFF0FC0
.equ kernel_atomic_base, 0xFFFF0FFF
#if defined(__ARM_HAVE_LDREX_STREX)
/*
* ===========================================================================
* ARMv6+ implementation
* ===========================================================================
*/
/* r0(addr) -> r0(old) */
__atomic_dec:
.fnstart
mov r1, r0 @ copy addr so we don't clobber it
1: ldrex r0, [r1] @ load current value into r0
sub r2, r0, #1 @ generate new value into r2
strex r3, r2, [r1] @ try to store new value; result in r3
cmp r3, #0 @ success?
bxeq lr @ yes, return
b 1b @ no, retry
.fnend
/* r0(addr) -> r0(old) */
__atomic_inc:
.fnstart
mov r1, r0
1: ldrex r0, [r1]
add r2, r0, #1
strex r3, r2, [r1]
cmp r3, #0
bxeq lr
b 1b
.fnend
/* r0(old) r1(new) r2(addr) -> r0(zero_if_succeeded) */
__atomic_cmpxchg:
.fnstart
1: mov ip, #2 @ ip=2 means "new != old"
ldrex r3, [r2] @ load current value into r3
teq r0, r3 @ new == old?
strexeq ip, r1, [r2] @ yes, try store, set ip to 0 or 1
teq ip, #1 @ strex failure?
beq 1b @ yes, retry
mov r0, ip @ return 0 on success, 2 on failure
bx lr
.fnend
/* r0(new) r1(addr) -> r0(old) */
__atomic_swap:
.fnstart
1: ldrex r2, [r1]
strex r3, r0, [r1]
teq r3, #0
bne 1b
mov r0, r2
bx lr
.fnend
#else /*not defined __ARM_HAVE_LDREX_STREX*/
/*
* ===========================================================================
* Pre-ARMv6 implementation
* ===========================================================================
*/
/* int __kernel_cmpxchg(int oldval, int newval, int* ptr) */
.equ kernel_cmpxchg, 0xFFFF0FC0
.equ kernel_atomic_base, 0xFFFF0FFF
/* r0(addr) -> r0(old) */
__atomic_dec:
.fnstart
.save {r4, lr}
@ -59,6 +124,7 @@ __atomic_dec:
bx lr
.fnend
/* r0(addr) -> r0(old) */
__atomic_inc:
.fnstart
.save {r4, lr}
@ -95,64 +161,16 @@ __atomic_cmpxchg:
ldmia sp!, {r4, lr}
bx lr
.fnend
#else
#define KUSER_CMPXCHG 0xffffffc0
/* r0(old) r1(new) r2(addr) -> r0(zero_if_succeeded) */
__atomic_cmpxchg:
stmdb sp!, {r4, lr}
mov r4, r0 /* r4 = save oldvalue */
1: add lr, pc, #4
mov r0, r4 /* r0 = oldvalue */
mov pc, #KUSER_CMPXCHG
bcs 2f /* swap was made. we're good, return. */
ldr r3, [r2] /* swap not made, see if it's because *ptr!=oldvalue */
cmp r3, r4
beq 1b
2: ldmia sp!, {r4, lr}
bx lr
/* r0(addr) -> r0(old) */
__atomic_dec:
stmdb sp!, {r4, lr}
mov r2, r0 /* address */
1: ldr r0, [r2] /* oldvalue */
add lr, pc, #4
sub r1, r0, #1 /* newvalue = oldvalue - 1 */
mov pc, #KUSER_CMPXCHG
bcc 1b /* no swap, try again until we get it right */
mov r0, ip /* swapped, return the old value */
ldmia sp!, {r4, lr}
bx lr
/* r0(addr) -> r0(old) */
__atomic_inc:
stmdb sp!, {r4, lr}
mov r2, r0 /* address */
1: ldr r0, [r2] /* oldvalue */
add lr, pc, #4
add r1, r0, #1 /* newvalue = oldvalue + 1 */
mov pc, #KUSER_CMPXCHG
bcc 1b /* no swap, try again until we get it right */
mov r0, ip /* swapped, return the old value */
ldmia sp!, {r4, lr}
bx lr
#endif
/* r0(new) r1(addr) -> r0(old) */
/* replaced swp instruction with ldrex/strex for ARMv6 & ARMv7 */
__atomic_swap:
#if defined (__ARM_HAVE_LDREX_STREX)
1: ldrex r2, [r1]
strex r3, r0, [r1]
teq r3, #0
bne 1b
mov r0, r2
mcr p15, 0, r0, c7, c10, 5 /* or, use dmb */
#else
.fnstart
swp r0, r0, [r1]
#endif
bx lr
.fnend
#endif /*not defined __ARM_HAVE_LDREX_STREX*/
/* __futex_wait(*ftx, val, *timespec) */
/* __futex_wake(*ftx, counter) */
@ -197,6 +215,8 @@ __futex_wait:
.fnend
__futex_wake:
.fnstart
.save {r4, r7}
stmdb sp!, {r4, r7}
mov r2, r1
mov r1, #FUTEX_WAKE
@ -204,6 +224,7 @@ __futex_wake:
swi #0
ldmia sp!, {r4, r7}
bx lr
.fnend
#else

15
libc/bionic/pthread.c
View file

@ -44,6 +44,7 @@
#include <assert.h>
#include <malloc.h>
#include <linux/futex.h>
#include <cutils/atomic-inline.h>
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);
@ -936,6 +937,7 @@ _normal_lock(pthread_mutex_t* mutex)
while (__atomic_swap(shared|2, &mutex->value ) != (shared|0))
__futex_syscall4(&mutex->value, wait_op, shared|2, 0);
}
ANDROID_MEMBAR_FULL();
}
/*
@ -945,6 +947,8 @@ _normal_lock(pthread_mutex_t* mutex)
static __inline__ void
_normal_unlock(pthread_mutex_t* mutex)
{
ANDROID_MEMBAR_FULL();
/* We need to preserve the shared flag during operations */
int shared = mutex->value & MUTEX_SHARED_MASK;
@ -1144,8 +1148,10 @@ int pthread_mutex_trylock(pthread_mutex_t *mutex)
/* Handle common case first */
if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
{
if (__atomic_cmpxchg(shared|0, shared|1, &mutex->value) == 0)
if (__atomic_cmpxchg(shared|0, shared|1, &mutex->value) == 0) {
ANDROID_MEMBAR_FULL();
return 0;
}
return EBUSY;
}
@ -1241,9 +1247,11 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
{
int wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE;
/* fast path for unconteded lock */
if (__atomic_cmpxchg(shared|0, shared|1, &mutex->value) == 0)
/* fast path for uncontended lock */
if (__atomic_cmpxchg(shared|0, shared|1, &mutex->value) == 0) {
ANDROID_MEMBAR_FULL();
return 0;
}
/* loop while needed */
while (__atomic_swap(shared|2, &mutex->value) != (shared|0)) {
@ -1252,6 +1260,7 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
__futex_syscall4(&mutex->value, wait_op, shared|2, &ts);
}
ANDROID_MEMBAR_FULL();
return 0;
}

14
libc/bionic/semaphore.c
View file

@ -30,6 +30,7 @@
#include <sys/time.h>
#include <sys/atomics.h>
#include <time.h>
#include <cutils/atomic-inline.h>
int sem_init(sem_t *sem, int pshared, unsigned int value)
{
@ -103,6 +104,7 @@ __atomic_dec_if_positive( volatile unsigned int* pvalue )
return old;
}
/* lock a semaphore */
int sem_wait(sem_t *sem)
{
if (sem == NULL) {
@ -116,6 +118,7 @@ int sem_wait(sem_t *sem)
__futex_wait(&sem->count, 0, 0);
}
ANDROID_MEMBAR_FULL();
return 0;
}
@ -130,8 +133,10 @@ int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout)
/* POSIX says we need to try to decrement the semaphore
* before checking the timeout value */
if (__atomic_dec_if_positive(&sem->count))
if (__atomic_dec_if_positive(&sem->count)) {
ANDROID_MEMBAR_FULL();
return 0;
}
/* check it as per Posix */
if (abs_timeout == NULL ||
@ -169,17 +174,21 @@ int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout)
return -1;
}
if (__atomic_dec_if_positive(&sem->count))
if (__atomic_dec_if_positive(&sem->count)) {
ANDROID_MEMBAR_FULL();
break;
}
}
return 0;
}
/* unlock a semaphore */
int sem_post(sem_t *sem)
{
if (sem == NULL)
return EINVAL;
ANDROID_MEMBAR_FULL();
if (__atomic_inc((volatile int*)&sem->count) >= 0)
__futex_wake(&sem->count, 1);
@ -194,6 +203,7 @@ int sem_trywait(sem_t *sem)
}
if (__atomic_dec_if_positive(&sem->count) > 0) {
ANDROID_MEMBAR_FULL();
return 0;
} else {
errno = EAGAIN;