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futex: restartable futex_wait

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LTP test sigaction_16_24 fails, because it expects sem_wait to be restarted
if SA_RESTART is set.  sem_wait is implemented with futex_wait, that
currently doesn't support being restarted.  Ulrich confirms that the call
should be restartable.

Implement a restart_block method to handle the relative timeout, and allow
restarts.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2007-05-08 00:26:43 -07:00 committed by Linus Torvalds
parent 9adef58b1d
commit 72c1bbf308
1 changed files with 51 additions and 5 deletions
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56
kernel/futex.c
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@ -980,12 +980,15 @@ static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb)
drop_futex_key_refs(&q->key);
}
static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
static long futex_wait_restart(struct restart_block *restart);
static int futex_wait_abstime(u32 __user *uaddr, u32 val,
int timed, unsigned long abs_time)
{
struct task_struct *curr = current;
DECLARE_WAITQUEUE(wait, curr);
struct futex_hash_bucket *hb;
struct futex_q q;
unsigned long time_left = 0;
u32 uval;
int ret;
@ -1065,8 +1068,21 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
* !list_empty() is safe here without any lock.
* q.lock_ptr != 0 is not safe, because of ordering against wakeup.
*/
if (likely(!list_empty(&q.list)))
time = schedule_timeout(time);
time_left = 0;
if (likely(!list_empty(&q.list))) {
unsigned long rel_time;
if (timed) {
unsigned long now = jiffies;
if (time_after(now, abs_time))
rel_time = 0;
else
rel_time = abs_time - now;
} else
rel_time = MAX_SCHEDULE_TIMEOUT;
time_left = schedule_timeout(rel_time);
}
__set_current_state(TASK_RUNNING);
/*
@ -1077,13 +1093,25 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
/* If we were woken (and unqueued), we succeeded, whatever. */
if (!unqueue_me(&q))
return 0;
if (time == 0)
if (time_left == 0)
return -ETIMEDOUT;
/*
* We expect signal_pending(current), but another thread may
* have handled it for us already.
*/
return -EINTR;
if (time_left == MAX_SCHEDULE_TIMEOUT)
return -ERESTARTSYS;
else {
struct restart_block *restart;
restart = &current_thread_info()->restart_block;
restart->fn = futex_wait_restart;
restart->arg0 = (unsigned long)uaddr;
restart->arg1 = (unsigned long)val;
restart->arg2 = (unsigned long)timed;
restart->arg3 = abs_time;
return -ERESTART_RESTARTBLOCK;
}
out_unlock_release_sem:
queue_unlock(&q, hb);
@ -1093,6 +1121,24 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
return ret;
}
static int futex_wait(u32 __user *uaddr, u32 val, unsigned long rel_time)
{
int timed = (rel_time != MAX_SCHEDULE_TIMEOUT);
return futex_wait_abstime(uaddr, val, timed, jiffies+rel_time);
}
static long futex_wait_restart(struct restart_block *restart)
{
u32 __user *uaddr = (u32 __user *)restart->arg0;
u32 val = (u32)restart->arg1;
int timed = (int)restart->arg2;
unsigned long abs_time = restart->arg3;
restart->fn = do_no_restart_syscall;
return (long)futex_wait_abstime(uaddr, val, timed, abs_time);
}
/*
* Userspace tried a 0 -> TID atomic transition of the futex value
* and failed. The kernel side here does the whole locking operation: