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List:       squeak-vm-dev
Subject:    Re: [Vm-dev] [Pharo-dev] Problem with OSSubprocess / signals / heartbeat ?
From:       Eliot Miranda <eliot.miranda () gmail ! com>
Date:       2017-03-31 14:31:10
Message-ID: F1F98C96-4B47-46B1-A169-E9F16EDC1B96 () gmail ! com
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Hi Levente,

> On Mar 31, 2017, at 6:42 AM, Levente Uzonyi <leves@caesar.elte.hu> wrote:
> 
> > On Thu, 30 Mar 2017, Eliot Miranda wrote:
> > 
> > Once the active process is in a tight loop the delay is effectively 
> disabled because the tight loop effectively shuts out the heartbeat thread and \
> hence the system never notices that the delay has expired. 
> I think that won't happen, because the process scheduler (O(1), CFS, BFS) on linux \
> is not cooperative. So, the kernel will periodically preempt the main thread and \
> run the heartbeat thread no matter what their priorities are. The higher priority \
> only provides lower jitter on the heartbeat thread.

It did happen.  In 2009 Andreas and I demonstrated it on Linux. Yes it may be the \
case that certain Linux kernel versions fix the issue but the only reliable way is to \
have the heartbeat thread run at a higher priority than the Smalltalk thread.
> 
> Levente


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