Messages in this thread | | | From | Mike Frysinger <> | Date | Wed, 24 Nov 2010 03:33:02 -0500 | Subject | Re: [PATCH] hrtimer: make epoll_wait() use the hrtimer range feature |
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On Sun, Aug 8, 2010 at 18:45, Shawn Bohrer wrote: > @@ -1116,18 +1113,22 @@ static int ep_send_events(struct eventpoll *ep, > static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, > int maxevents, long timeout) > { > - int res, eavail; > + int res, eavail, timed_out = 0; > unsigned long flags; > - long jtimeout; > + long slack; > wait_queue_t wait; > - > - /* > - * Calculate the timeout by checking for the "infinite" value (-1) > - * and the overflow condition. The passed timeout is in milliseconds, > - * that why (t * HZ) / 1000. > - */ > - jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? > - MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; > + struct timespec end_time; > + ktime_t expires, *to = NULL; > + > + if (timeout > 0) { > + ktime_get_ts(&end_time); > + timespec_add_ns(&end_time, (u64)timeout * NSEC_PER_MSEC); > + slack = estimate_accuracy(&end_time); > + to = &expires; > + *to = timespec_to_ktime(end_time); > + } else if (timeout == 0) { > + timed_out = 1; > + } > > retry: > spin_lock_irqsave(&ep->lock, flags); > @@ -1149,7 +1150,7 @@ retry: > * to TASK_INTERRUPTIBLE before doing the checks. > */ > set_current_state(TASK_INTERRUPTIBLE); > - if (!list_empty(&ep->rdllist) || !jtimeout) > + if (!list_empty(&ep->rdllist) || timed_out) > break; > if (signal_pending(current)) { > res = -EINTR; > @@ -1157,7 +1158,9 @@ retry: > } > > spin_unlock_irqrestore(&ep->lock, flags); > - jtimeout = schedule_timeout(jtimeout); > + if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) > + timed_out = 1; > + > spin_lock_irqsave(&ep->lock, flags); > } > __remove_wait_queue(&ep->wq, &wait);
this code introduces a warning: fs/eventpoll.c: In function ‘ep_poll’: fs/eventpoll.c:1119: warning: ‘slack’ may be used uninitialized in this function
looks to me like you arent properly handling negative timeouts. certainly epoll_wait() passes the timeout value straight from userspace to ep_poll() without any error checking, so if userspace passes a negative timeout value, it looks like "slack" will be used uninitialized. -mike
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