Messages in this thread | | | Date | Tue, 10 Nov 2015 09:18:12 +0200 | From | Kalle Kankare <> | Subject | During high load wait_event_timeout might return a wrong value |
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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 ?
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