Re: [Threads-devel] Fwd: cond.timed_wait() returns way after deadline?

Subject: Re: [Threads-devel] Fwd: cond.timed_wait() returns way after deadline?
From: Stefan Steuerwald (salsasepp_at_[hidden])
Date: 2009-07-09 09:17:31

2009/7/9 Frank Mori Hess <frank.hess_at_[hidden]>:
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> On Thursday 09 July 2009, Stefan Steuerwald wrote:
>> Dear threaders,
>>
>> I have this code:
>>
>> Â  Â  Â  Â unique_lock<mutex> lock(mut);
>> Â  Â  Â  Â system_time deadline = get_system_time() + timeout;
>> Â  Â  Â  Â while( some_pred() ) {
>> Â  Â  Â  Â  Â  Â  Â  Â if( ! cond.timed_wait( lock, deadline ) )
>> Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â break;
>> Â  Â  Â  Â }
>>
>> boost 1.37.0 on a linux 2.6.30.1 kernel.
>> Works fine 99% of the time. Sometimes however, I see timed_wait()
>> returning several seconds AFTER the deadline (timeout is 5000ms).
>> I wonder what could cause such behaviour?
>
> You didn't show the notify end of the code. Â Does it lock the same mutex
> before calling notify?

Sorry, right. It looks like this:

        unique_lock<mutex> lock(mut);
        // some variable updates here
        lock.unlock();
        cond.notify_all();