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futex: restartable futex_wait
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>
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@ -980,12 +980,15 @@ static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb)
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drop_futex_key_refs(&q->key);
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}
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static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
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static long futex_wait_restart(struct restart_block *restart);
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static int futex_wait_abstime(u32 __user *uaddr, u32 val,
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int timed, unsigned long abs_time)
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{
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struct task_struct *curr = current;
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DECLARE_WAITQUEUE(wait, curr);
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struct futex_hash_bucket *hb;
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struct futex_q q;
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unsigned long time_left = 0;
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u32 uval;
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int ret;
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@ -1065,8 +1068,21 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
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* !list_empty() is safe here without any lock.
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* q.lock_ptr != 0 is not safe, because of ordering against wakeup.
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*/
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if (likely(!list_empty(&q.list)))
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time = schedule_timeout(time);
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time_left = 0;
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if (likely(!list_empty(&q.list))) {
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unsigned long rel_time;
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if (timed) {
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unsigned long now = jiffies;
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if (time_after(now, abs_time))
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rel_time = 0;
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else
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rel_time = abs_time - now;
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} else
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rel_time = MAX_SCHEDULE_TIMEOUT;
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time_left = schedule_timeout(rel_time);
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}
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__set_current_state(TASK_RUNNING);
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/*
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@ -1077,13 +1093,25 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
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/* If we were woken (and unqueued), we succeeded, whatever. */
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if (!unqueue_me(&q))
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return 0;
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if (time == 0)
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if (time_left == 0)
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return -ETIMEDOUT;
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/*
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* We expect signal_pending(current), but another thread may
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* have handled it for us already.
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*/
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return -EINTR;
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if (time_left == MAX_SCHEDULE_TIMEOUT)
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return -ERESTARTSYS;
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else {
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struct restart_block *restart;
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restart = ¤t_thread_info()->restart_block;
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restart->fn = futex_wait_restart;
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restart->arg0 = (unsigned long)uaddr;
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restart->arg1 = (unsigned long)val;
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restart->arg2 = (unsigned long)timed;
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restart->arg3 = abs_time;
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return -ERESTART_RESTARTBLOCK;
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}
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out_unlock_release_sem:
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queue_unlock(&q, hb);
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@ -1093,6 +1121,24 @@ static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
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return ret;
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}
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static int futex_wait(u32 __user *uaddr, u32 val, unsigned long rel_time)
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{
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int timed = (rel_time != MAX_SCHEDULE_TIMEOUT);
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return futex_wait_abstime(uaddr, val, timed, jiffies+rel_time);
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}
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static long futex_wait_restart(struct restart_block *restart)
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{
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u32 __user *uaddr = (u32 __user *)restart->arg0;
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u32 val = (u32)restart->arg1;
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int timed = (int)restart->arg2;
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unsigned long abs_time = restart->arg3;
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restart->fn = do_no_restart_syscall;
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return (long)futex_wait_abstime(uaddr, val, timed, abs_time);
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}
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/*
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* Userspace tried a 0 -> TID atomic transition of the futex value
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* and failed. The kernel side here does the whole locking operation:
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