Experimental Physics and
Industrial Control System

<[email protected]> · Fri, 28 Jan 2011 16:16:45 +0000

Hi Andrew

The PREEMPT_RT patch makes the kernel fully pre-emptive (leading to
improved maximum latency) and adds support for priority inheritance
mutexes. There are no user space API changes, the code to use
_POSIX_THREAD_PRIORITY_SCHEDULING and _POSIX_THREAD_PRIO_INHERIT is
already in libCom (if disabled by default). I'd like to use the
epicsMessageQueue from a high priority thread but the send and receive
functions may calloc an eventNode, and that might cause a page fault or
block my thread on the malloc lock. I'd like to be able to pre-allocate
the eventNodes because I know the maximum number of threads that may
wait on the queue in advance.

James

> -----Original Message-----
> From: Andrew Johnson [mailto:[email protected]]
> Sent: 28 January 2011 15:50
> To: [email protected]
> Cc: Rowland, James (DLSLtd,RAL,DIA)
> Subject: Re: epicsMessageQueue Linux PREEMPT_RT
> 
> Hi James,
> 
> On Friday 28 January 2011 06:48:54 [email protected] wrote:
> >
> > I'd like to use the epicsMessageQueue on Linux PREEMPT_RT, but the
> event
> > nodes are calloc'ed at runtime. I can fill up the event node free
> list
> > by creating some dummy threads at initialization, is there interest
> in a
> > patch to add a call for this pre-allocation on Linux?
> 
> You've lost me, I know very little (assume nothing) about what's
> different
> with Linux PREEMPT_RT. Can you explain more what you're trying to do
> and how
> our existing code is deficient for that purpose.
> 
> - Andrew
> --
> If a man is offered a fact which goes against his instincts, he will
> scrutinize it closely, and unless the evidence is overwhelming, he
will
> refuse to believe it.  If, on the other hand, he is offered something
> which affords a reason for acting in accordance to his instincts, he
> will accept it even on the slightest evidence.  -- Bertrand Russell

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System