[PATCH] Fix a pthreadpool race

[jim]

On 12/15/2017 10:57 AM, Ralph Wuerthner via samba-technical wrote:
> On 15.12.2017 12:54, Volker Lendecke wrote:
>> That is of course a lot more elegant. Looking through the code I have
>> one concern: The threads are kept busy throughout the fork, which is
>> good. I would like to see a good argument why the while(num_idle!=0)
>> loop in pthreadpool_prepare_pool deterministically terminates. It's
>> probably not really supported right now, but what if a helper thread
>> creates new jobs? This might keep the helper threads busy, and they
>> might re-enter idle state over and over again when prepare_pool checks
>> for idle threads. More parallelism is good, your patch is of course
>> simpler and thus preferrable, but I would feel better if we had a
>> "proof" that prepare_pool never runs into an endless loop. Keep in
>> mind that every single small race we open will eventually be hit at a
>> customer installation :-)
>
> I see, this is a valid concern. Let me check if I can harden the code 
> to guarantee that pthreadpool_prepare_pool will not end in an endless 
> loop.

You could add a loop counter with a limit value test to generate an 
error if exceeded.