Message-ID: <4DEDF366.6000706@cfl.rr.com>
Date: Tue, 07 Jun 2011 05:46:14 -0400
From: Mark Hounschell <dmarkh@cfl.rr.com>
Reply-To: dmarkh@cfl.rr.com
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.17) Gecko/20110414 SUSE/3.1.10 Thunderbird/3.1.10
MIME-Version: 1.0
To: Monica Puig-Pey <puigpeym@unican.es>
CC: dmarkh@cfl.rr.com, markh@compro.net,
        Rolando Martins <rolando.martins@gmail.com>,
        linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Changing Kernel thread priorities
References: <4DEA1BA9.7020303@unican.es><4DEA1F22.6000603@unican.es><4DEA255				B.2050503@unican.es><4DECBE44.2070803@unican.es> 			<BANLkTi=xSJOgY735PE44YtkQmrdhgetGdQ@mail.gmail.com> 		<4DECC0DF.8070209@unican.es> <4DED051A.6020702@compro.net> <4DEDE411.6010807@unican.es> <4DEDEBFF.10907@cfl.rr.com>
In-Reply-To: <4DEDEBFF.10907@cfl.rr.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 4180
Lines: 121

On 06/07/2011 05:14 AM, Mark Hounschell wrote:
> On 06/07/2011 04:40 AM, Monica Puig-Pey wrote:
>> El 06/06/11 18:49, Mark Hounschell escribi?:
>>> On 06/06/2011 07:58 AM, Monica Puig-Pey wrote:
>>>> El 06/06/11 13:54, Rolando Martins escribi?:
>>>>> Hi,
>>>>> I use the following:
>>>>>
>>>>> PIDs=$(ps -eLo pid,cls,rtprio,pri,nice,cmd | grep -i "irq" | awk '{
>>>>> print $1; }' | xargs echo)
>>>>> for i in $PIDs
>>>>> do
>>>>> ret=$(chrt -f -p 99 $i)
>>>>> done
>>>>>
>>>>> This will change the kernel thread associated with an irq handler to
>>>>> RT FIFO prio 99.
>>>>> Just change the script to your specific interrupt.
>>>>>
>>>>> Hope it helps,
>>>>> Rolando
>>>>>
>>>>> On Mon, Jun 6, 2011 at 12:47 PM, Monica Puig-Pey<puigpeym@unican.es>
>>>>> wrote:
>>>>>> I am writing a driver which has one kernel thread associated with it.
>>>>>> I want to change the priority of this thread, so that I can specify the
>>>>>> order in which it is scheduled following an interrupt.
>>>>>> I'm using:
>>>>>>
>>>>>> sched_setscheduler(struct task_struct *, int, struct sched_param *);
>>>>>>
>>>>>> but it doesn't work. I tried to change the priority from the
>>>>>> init_module,
>>>>>> and also from the Kernel Thread, but there is no way.
>>>>>>
>>>>>> Kernel version is 2.6.31-11-rt
>>>>>>
>>>>>> What do I call to change a kernel thread priority?
>>>>>>
>>>>>> Thanks you very much
>>>>>>
>>>>>> M?nica
>>>>>>
>>>>>> --
>>>>>> To unsubscribe from this list: send the line "unsubscribe
>>>>>> linux-rt-users" in
>>>>>> the body of a message to majordomo@vger.kernel.org
>>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>>>>
>>>>
>>>> I need to change the priority from inside the driver, when creating the
>>>> kernel thread.
>>>> Your script is useful but it is done in user context,
>>>> Any other help please?
>>>
>>> What I do is record the PID of the thread in the driver, then create an
>>> IOCTL for your driver that user land can call that either returns the
>>> PID so you can do it in user land, or cause the IOCTL code to do it in
>>> the driver.
>>>
>>> The same can be done with the affinity of the IRQ if you record the IRQ
>>> number.
>>>
>>> Mark
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe
>>> linux-rt-users" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>> But I don't have de PID of my Kthread, I only have the task_struc * that
>> gives me the function:
>>
>> struct task_struct *kthread_create(int (*threadfn)(void *data),
>> void *data,
>> const char namefmt[], ...)
>>
>> How could I get the PID, and which function should I use in the IOCTL
>> (kernel context) for changing its priority?
>>
>
> The PID can be obtained from within the interrupt handler its self via
> current->pid.
> Obviously an interrupt has to occur first but after one interrupt you have it.
>
> Actually I had forgot how I handled this. Where I change the RT priority
> and cpu affinity is in what used to be called the Bottom Half and the IOCTL
> referred to above simply tells the BH to do it and with what values.
>

In interrupt handler code snippet:

struct task_struct *TSK;
struct sched_param PARAM = {.sched_priority = MAX_RT_PRIO };

         TSK = current;

Code snippet from BH:

         if (((rtom_rtprio != 0) &&
              (rtom_rtprio != PARAM.sched_priority)) ||
              (my_rtom_rtprio[BOARD] != rtom_rtprio)) {

                 PARAM.sched_priority = rtom_rtprio;
                 my_rtom_rtprio[COUNT] = rtom_rtprio;
                 sched_setscheduler(TSK, SCHED_FIFO, &PARAM);

                 set_cpus_allowed(TSK, rtom_devices[BOARD].irq_cpu_mask);
                 rtom_devices[BOARD].irq_task_pid = TSK->pid;
        }

rtom_rtprio and irq_cpu_mask are set by userland via an IOCTL. An interrupt 
must occur for this to happen and my BOARD never shares IRQs.

Mark

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/