generic-library/bionic
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Implement pthread_condattr_{get,set}clock.

Browse Source 
We only support CLOCK_REALTIME and CLOCK_MONOTONIC for now,
so we us a single bit from pthread_cond_t->value to denote
the clock type. Note that this reduces the width of the counter
to 30 bits, but this should be large enough for all practical
purposes.

bug: 13232338

Change-Id: I857e7da64b3ecbb23eeac7c9f3fbd460f60231bd
This commit is contained in:
Narayan Kamath
2014-03-03 15:38:51 +00:00
parent 2c7c79e6e5
commit 51e6cb33e3
3 changed files with 116 additions and 35 deletions
Download Patch File Download Diff File Expand all files Collapse all files

87
libc/bionic/pthread_cond.cpp
View File

@@ -32,6 +32,7 @@
#include <limits.h>
#include <sys/atomics.h>
#include <sys/mman.h>
#include <time.h>
#include <unistd.h>
#include "pthread_internal.h"
@@ -42,30 +43,55 @@
#include "private/bionic_tls.h"
#include "private/thread_private.h"
// We use one bit in pthread_condattr_t (long) values as the 'shared' flag
// and one bit for the clock type (CLOCK_REALTIME is ((clockid_t) 1), and
// CLOCK_MONOTONIC is ((clockid_t) 0).). The rest of the bits are a counter.
//
// The 'value' field pthread_cond_t has the same layout.
#define COND_SHARED_MASK 0x0001
#define COND_CLOCK_MASK 0x0002
#define COND_COUNTER_STEP 0x0004
#define COND_FLAGS_MASK (COND_SHARED_MASK | COND_CLOCK_MASK)
#define COND_COUNTER_MASK (~COND_FLAGS_MASK)
#define COND_IS_SHARED(c) (((c) & COND_SHARED_MASK) != 0)
#define COND_GET_CLOCK(c) (((c) & COND_CLOCK_MASK) >> 1)
#define COND_SET_CLOCK(attr, c) ((attr) | (c << 1))
int pthread_condattr_init(pthread_condattr_t* attr) {
if (attr == NULL) {
return EINVAL;
}
*attr = PTHREAD_PROCESS_PRIVATE;
*attr = 0;
*attr |= PTHREAD_PROCESS_PRIVATE;
*attr |= (CLOCK_REALTIME << 1);
return 0;
}
int pthread_condattr_getpshared(const pthread_condattr_t* attr, int* pshared) {
if (attr == NULL || pshared == NULL) {
return EINVAL;
}
*pshared = *attr;
*pshared = static_cast<int>(COND_IS_SHARED(*attr));
return 0;
}
int pthread_condattr_setpshared(pthread_condattr_t* attr, int pshared) {
if (attr == NULL) {
return EINVAL;
}
if (pshared != PTHREAD_PROCESS_SHARED && pshared != PTHREAD_PROCESS_PRIVATE) {
return EINVAL;
}
*attr = pshared;
*attr |= pshared;
return 0;
}
int pthread_condattr_getclock(const pthread_condattr_t* attr, clockid_t* clock) {
*clock = COND_GET_CLOCK(*attr);
return 0;
}
int pthread_condattr_setclock(pthread_condattr_t* attr, clockid_t clock) {
if (clock != CLOCK_MONOTONIC && clock != CLOCK_REALTIME) {
return EINVAL;
}
*attr = COND_SET_CLOCK(*attr, clock);
return 0;
}
@@ -77,13 +103,6 @@ int pthread_condattr_destroy(pthread_condattr_t* attr) {
return 0;
}
// We use one bit in condition variable values as the 'shared' flag
// The rest is a counter.
#define COND_SHARED_MASK 0x0001
#define COND_COUNTER_INCREMENT 0x0002
#define COND_COUNTER_MASK (~COND_SHARED_MASK)
#define COND_IS_SHARED(c) (((c)->value & COND_SHARED_MASK) != 0)
// XXX *technically* there is a race condition that could allow
// XXX a signal to be missed. If thread A is preempted in _wait()
@@ -97,10 +116,10 @@ int pthread_cond_init(pthread_cond_t* cond, const pthread_condattr_t* attr) {
return EINVAL;
}
cond->value = 0;
if (attr != NULL && *attr == PTHREAD_PROCESS_SHARED) {
cond->value |= COND_SHARED_MASK;
if (attr != NULL) {
cond->value = (*attr & COND_FLAGS_MASK);
} else {
cond->value = 0;
}
return 0;
@@ -123,10 +142,10 @@ static int __pthread_cond_pulse(pthread_cond_t* cond, int counter) {
return EINVAL;
}
long flags = (cond->value & ~COND_COUNTER_MASK);
int flags = (cond->value & COND_FLAGS_MASK);
while (true) {
long old_value = cond->value;
long new_value = ((old_value - COND_COUNTER_INCREMENT) & COND_COUNTER_MASK) | flags;
int old_value = cond->value;
int new_value = ((old_value - COND_COUNTER_STEP) & COND_COUNTER_MASK) | flags;
if (__bionic_cmpxchg(old_value, new_value, &cond->value) == 0) {
break;
}
@@ -142,7 +161,7 @@ static int __pthread_cond_pulse(pthread_cond_t* cond, int counter) {
// hold the mutex, they're subject to race conditions anyway.
ANDROID_MEMBAR_FULL();
__futex_wake_ex(&cond->value, COND_IS_SHARED(cond), counter);
__futex_wake_ex(&cond->value, COND_IS_SHARED(cond->value), counter);
return 0;
}
@@ -151,7 +170,7 @@ int __pthread_cond_timedwait_relative(pthread_cond_t* cond, pthread_mutex_t* mut
int old_value = cond->value;
pthread_mutex_unlock(mutex);
int status = __futex_wait_ex(&cond->value, COND_IS_SHARED(cond), old_value, reltime);
int status = __futex_wait_ex(&cond->value, COND_IS_SHARED(cond->value), old_value, reltime);
pthread_mutex_lock(mutex);
if (status == -ETIMEDOUT) {
@@ -186,21 +205,23 @@ int pthread_cond_signal(pthread_cond_t* cond) {
}
int pthread_cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex) {
return __pthread_cond_timedwait(cond, mutex, NULL, CLOCK_REALTIME);
return __pthread_cond_timedwait(cond, mutex, NULL, COND_GET_CLOCK(cond->value));
}
int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t * mutex, const timespec *abstime) {
return __pthread_cond_timedwait(cond, mutex, abstime, CLOCK_REALTIME);
return __pthread_cond_timedwait(cond, mutex, abstime, COND_GET_CLOCK(cond->value));
}
// TODO: this exists only for backward binary compatibility.
int pthread_cond_timedwait_monotonic(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) {
#if !defined(__LP64__)
// TODO: this exists only for backward binary compatibility on 32 bit platforms.
extern "C" int pthread_cond_timedwait_monotonic(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) {
return __pthread_cond_timedwait(cond, mutex, abstime, CLOCK_MONOTONIC);
}
int pthread_cond_timedwait_monotonic_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) {
extern "C" int pthread_cond_timedwait_monotonic_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) {
return __pthread_cond_timedwait(cond, mutex, abstime, CLOCK_MONOTONIC);
}
#endif // !defined(__LP64__)
int pthread_cond_timedwait_relative_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* reltime) {
return __pthread_cond_timedwait_relative(cond, mutex, reltime);