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unify and overhaul timed futex waits

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new features:

- FUTEX_WAIT_BITSET op will be used for timed waits if available. this
  saves a call to clock_gettime.

- error checking for the timespec struct is now inside __timedwait so
  it doesn't need to be duplicated everywhere. cond_timedwait still
  needs to duplicate it to avoid unlocking the mutex, though.

- pushing and popping the cancellation handler is delegated to
  __timedwait, and cancellable/non-cancellable waits are unified.
This commit is contained in:
Rich Felker 2011-08-02 21:11:36 -04:00
commit ec381af902
10 changed files with 56 additions and 53 deletions
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53
src/thread/__timedwait.c
View file

@ -1,23 +1,48 @@
#include <pthread.h>
#include <time.h>
#include <errno.h>
#include "futex.h"
#include "syscall.h"
int __timedwait(volatile int *addr, int val, clockid_t clk, const struct timespec *at, int priv)
static int do_wait(volatile int *addr, int val, clockid_t clk, const struct timespec *at, int cp, int priv)
{
int r;
struct timespec to;
if (at) {
clock_gettime(clk, &to);
to.tv_sec = at->tv_sec - to.tv_sec;
if ((to.tv_nsec = at->tv_nsec - to.tv_nsec) < 0) {
to.tv_sec--;
to.tv_nsec += 1000000000;
}
if (to.tv_sec < 0) return ETIMEDOUT;
int r, flag = 0;
struct timespec to, *top=0;
if (!at) goto notimeout;
if (at->tv_nsec >= 1000000000UL)
return EINVAL;
if (clk == CLOCK_REALTIME || clk == CLOCK_MONOTONIC) {
if (clk == CLOCK_REALTIME) flag = FUTEX_CLOCK_REALTIME;
if (cp) r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT_BITSET|flag, val, at, 0, -1);
else r = -__syscall(SYS_futex, addr, FUTEX_WAIT_BITSET|flag, val, at, 0, -1);
if (r != ENOSYS) goto done;
}
if (priv) priv = 128; priv=0;
r = -__syscall(SYS_futex, (long)addr, FUTEX_WAIT | priv, val, at ? (long)&to : 0);
if (r == ETIMEDOUT || r == EINTR) return r;
if (clock_gettime(clk, &to)) return EINVAL;
to.tv_sec = at->tv_sec - to.tv_sec;
if ((to.tv_nsec = at->tv_nsec - to.tv_nsec) < 0) {
to.tv_sec--;
to.tv_nsec += 1000000000;
}
if (to.tv_sec < 0) return ETIMEDOUT;
top = &to;
notimeout:
if (cp) r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT, val, top);
else r = -__syscall(SYS_futex, addr, FUTEX_WAIT, val, top);
done:
if (r == EINTR || r == EINVAL || r == ETIMEDOUT) return r;
return 0;
}
int __timedwait(volatile int *addr, int val, clockid_t clk, const struct timespec *at, void (*cleanup)(void *), void *arg, int priv)
{
int r;
if (cleanup) {
pthread_cleanup_push(cleanup, arg);
r = do_wait(addr, val, clk, at, 1, priv);
pthread_cleanup_pop(0);
} else {
r = do_wait(addr, val, clk, at, 0, priv);
}
return r;
}