factor cancellation cleanup push/pop out of futex __timedwait function

previously, the __timedwait function was optionally a cancellation
point depending on whether it was passed a pointer to a cleaup
function and context to register. as of now, only one caller actually
used such a cleanup function (and it may face removal soon); most
callers either passed a null pointer to disable cancellation or a
dummy cleanup function.

now, __timedwait is never a cancellation point, and __timedwait_cp is
the cancellable version. this makes the intent of the calling code
more obvious and avoids ugly dummy functions and long argument lists.
This commit is contained in:
Rich Felker 2015-03-02 17:46:22 -05:00
parent 76ca7a5446
commit 0fc317d83c
9 changed files with 25 additions and 27 deletions

View File

@ -61,7 +61,7 @@ int aio_suspend(const struct aiocb *const cbs[], int cnt, const struct timespec
break;
}
ret = __timedwait(pfut, expect, CLOCK_MONOTONIC, ts?&at:0, 0, 0, 1);
ret = __timedwait(pfut, expect, CLOCK_MONOTONIC, ts?&at:0, 1);
if (ret) {
errno = ret==ETIMEDOUT ? EAGAIN : ret;

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@ -107,7 +107,8 @@ int __libc_sigprocmask(int, const sigset_t *, sigset_t *);
void __lock(volatile int *);
void __unmapself(void *, size_t);
int __timedwait(volatile int *, int, clockid_t, const struct timespec *, void (*)(void *), void *, int);
int __timedwait(volatile int *, int, clockid_t, const struct timespec *, int);
int __timedwait_cp(volatile int *, int, clockid_t, const struct timespec *, int);
void __wait(volatile int *, volatile int *, int, int);
static inline void __wake(volatile void *addr, int cnt, int priv)
{

View File

@ -3,15 +3,15 @@
#include <errno.h>
#include "futex.h"
#include "syscall.h"
#include "pthread_impl.h"
int __pthread_setcancelstate(int, int *);
int __clock_gettime(clockid_t, struct timespec *);
int __timedwait(volatile int *addr, int val,
clockid_t clk, const struct timespec *at,
void (*cleanup)(void *), void *arg, int priv)
int __timedwait_cp(volatile int *addr, int val,
clockid_t clk, const struct timespec *at, int priv)
{
int r, cs;
int r;
struct timespec to, *top=0;
if (priv) priv = 128;
@ -28,15 +28,19 @@ int __timedwait(volatile int *addr, int val,
top = &to;
}
if (!cleanup) __pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
pthread_cleanup_push(cleanup, arg);
r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT|priv, val, top);
if (r == ENOSYS) r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT, val, top);
if (r != EINTR && r != ETIMEDOUT && r != ECANCELED) r = 0;
pthread_cleanup_pop(0);
if (!cleanup) __pthread_setcancelstate(cs, 0);
return r;
}
int __timedwait(volatile int *addr, int val,
clockid_t clk, const struct timespec *at, int priv)
{
int cs, r;
__pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
r = __timedwait_cp(addr, val, clk, at, priv);
__pthread_setcancelstate(cs, 0);
return r;
}

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@ -64,10 +64,6 @@ enum {
LEAVING,
};
static void dummy(void *arg)
{
}
int __pthread_cond_timedwait(pthread_cond_t *restrict c, pthread_mutex_t *restrict m, const struct timespec *restrict ts)
{
struct waiter node = { 0 };
@ -104,7 +100,7 @@ int __pthread_cond_timedwait(pthread_cond_t *restrict c, pthread_mutex_t *restri
__pthread_setcancelstate(PTHREAD_CANCEL_MASKED, &cs);
do e = __timedwait(fut, seq, clock, ts, dummy, 0, !shared);
do e = __timedwait_cp(fut, seq, clock, ts, !shared);
while (*fut==seq && (!e || e==EINTR));
if (e == EINTR) e = 0;

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@ -3,15 +3,11 @@
int __munmap(void *, size_t);
static void dummy(void *p)
{
}
int __pthread_join(pthread_t t, void **res)
{
int tmp;
pthread_testcancel();
while ((tmp = t->tid)) __timedwait(&t->tid, tmp, 0, 0, dummy, 0, 0);
while ((tmp = t->tid)) __timedwait_cp(&t->tid, tmp, 0, 0, 0);
if (res) *res = t->result;
if (t->map_base) __munmap(t->map_base, t->map_size);
return 0;

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@ -24,7 +24,7 @@ int __pthread_mutex_timedlock(pthread_mutex_t *restrict m, const struct timespec
a_inc(&m->_m_waiters);
t = r | 0x80000000;
a_cas(&m->_m_lock, r, t);
r = __timedwait(&m->_m_lock, t, CLOCK_REALTIME, at, 0, 0, priv);
r = __timedwait(&m->_m_lock, t, CLOCK_REALTIME, at, priv);
a_dec(&m->_m_waiters);
if (r && r != EINTR) break;
}

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@ -15,7 +15,7 @@ int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rw, const struct times
t = r | 0x80000000;
a_inc(&rw->_rw_waiters);
a_cas(&rw->_rw_lock, r, t);
r = __timedwait(&rw->_rw_lock, t, CLOCK_REALTIME, at, 0, 0, rw->_rw_shared^128);
r = __timedwait(&rw->_rw_lock, t, CLOCK_REALTIME, at, rw->_rw_shared^128);
a_dec(&rw->_rw_waiters);
if (r && r != EINTR) return r;
}

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@ -15,7 +15,7 @@ int pthread_rwlock_timedwrlock(pthread_rwlock_t *restrict rw, const struct times
t = r | 0x80000000;
a_inc(&rw->_rw_waiters);
a_cas(&rw->_rw_lock, r, t);
r = __timedwait(&rw->_rw_lock, t, CLOCK_REALTIME, at, 0, 0, rw->_rw_shared^128);
r = __timedwait(&rw->_rw_lock, t, CLOCK_REALTIME, at, rw->_rw_shared^128);
a_dec(&rw->_rw_waiters);
if (r && r != EINTR) return r;
}

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@ -19,8 +19,9 @@ int sem_timedwait(sem_t *restrict sem, const struct timespec *restrict at)
int r;
a_inc(sem->__val+1);
a_cas(sem->__val, 0, -1);
r = __timedwait(sem->__val, -1, CLOCK_REALTIME, at, cleanup, sem->__val+1, sem->__val[2]);
a_dec(sem->__val+1);
pthread_cleanup_push(cleanup, sem->__val+1);
r = __timedwait_cp(sem->__val, -1, CLOCK_REALTIME, at, sem->__val[2]);
pthread_cleanup_pop(1);
if (r && r != EINTR) {
errno = r;
return -1;