During high load wait_event_timeout might return a wrong value

[Kalle Kankare]

Hi,

The problem is that the call to might_sleep might sleep and the return value of wait_event_timeout does not account for the time slept in there.

The might_sleep includes a call to __schedule if CONFIG_PREEMPT_VOLUNTARY is defined.

A problematic scenario can be like the following:

- A driver calls wait_event_timeout with timeout = 10 jiffies, starts sleeping in might_sleep.
- An interrupt handler sets the condition true at 5 jiffies and calls wake_up for the waitqueue.
- Due to high load the might_sleep wakes up at 100 jiffies.
- In the next if the __wait_cond_timeout returns 1 without manipulating __ret.
- wait_event_timeout returns 10 where it should have returned 1 to denote that a timeout was reached.

Or am I misunderstanding what the return value should be ?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/