Re: Changing Kernel thread priorities

[Monica Puig-Pey]

El 06/06/11 18:49, Mark Hounschell escribió:
> On 06/06/2011 07:58 AM, Monica Puig-Pey wrote:
> > El 06/06/11 13:54, Rolando Martins escribió:
> > > 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@xxxxxxxxx>
> > > 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
> > > >
> > > > Mónica
> > > >
> > > > --
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> >
> > 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
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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?

Thank you so much for your help

Mónica
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