Heinz Häberle wrote:
>
> Steve Papacharalambous wrote:
> >
> > Philip N Daly wrote:
> > >
> > > Content-MD5: fVT3+tdeWfB8vwdyUSaZXQ==
> > >
> > > Hi,
> > >
> > > Not specifically a RTL/RTAI question but does anyone know how to
> > > "sleep" in a kernel module? Not something I want to do very often
> > > but I have a need right now. udelay appears to crash my kernel.
> > >
> > > Ta,
> > >
> > > +==================================================================+
> > > Phil Daly, NOAO/AURA, 950 N. Cherry Avenue, Tucson AZ 85719, U S A
> > > E-mail: [EMAIL PROTECTED] V-mail: (520) 318 8438 Fax: (520) 318 8360
> > >
> > > --- [rtl] ---
> > > To unsubscribe:
> > > echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR
> > > echo "unsubscribe rtl <Your_email>" | mail [EMAIL PROTECTED]
> > > ----
> > > For more information on Real-Time Linux see:
> > > http://www.rtlinux.org/~rtlinux/
> >
> > Hi Phil,
> >
> > For periods greater than a timer tick you can set current->timeout and
> > sleep on a wait queue. The timeout value is compared with jiffies every
> > time the scheduler runs, and if it is smaller than or equal to the
> > current time the scheduler will wake the process. For example:
> >
> > unsigned long time_delay;
> >
> > time_delay = jiffies + my_delay;
> >
> > current->timeout = time_delay;
> > current->state = TASK_INTERRUPTIBLE;
> > schedule();
> > current->timeout = 0;
> >
> > An alternative to this is to use kernel timers to dispatch a function at
> > some time in the future. For example:
> >
> > unsigned long time_delay;
> > struct timer_list my_timer;
> >
> > init_timer(&my_timer);
> > my_timer.function = <function to be called>;
> > my_timer.data = <any data to pass to the function>;
> > my_timer.expires = jiffies + time_delay;
> > add_timer(&my_timer);
> >
> > For very short delays use the kernel function udelay:
> >
> > #include <linux/udelay.h>
> > void udelay(unsigned long usecs);
> >
> > Remember that udelay is a busy waiting function, so other tasks cannot
> > run during the time lapse. The suggested maximum for this function is 1
> > millisecond.
> >
> > For more information on this topic Chapter 6 of Linux Device Drivers by
> > Rubini has some very useful details,
> >
> > Best regards,
> >
> > Steve
> >
>
> You talk about modules not in the rtl environment, did you?
> I use the function rtl_delay in my module instead, isn't this ok?
>
> Heinz
Hi Heinz,
Yeah, I was only considering the vanilla Linux kernel environment.
For RTLinux rtl_delay is okay for short delays. This is a nanosecond
version of the Linux kernel function and is a busy wait loop.
For RTAI you can use rt_busy_sleep(nanoseconds)
Incidentally my earlier mail on Linux kernel delays was incorrect for
later kernel versions. If, for example, you need to delay the execution
of a Linux kernel task for 20 msecs then one way of doing it is:
#include <linux/sched.h>
current->state = TASK_INTERRUPTIBLE;
#if LINUX_VERSION_CODE >= 0x02017F
schedule_timeout(20 * HZ / 1000);
#else
current->timeout = jiffies + 20 * HZ / 1000; // 20 ms
schedule();
#endif
Hope this helps,
Steve
--- [rtl] ---
To unsubscribe:
echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR
echo "unsubscribe rtl <Your_email>" | mail [EMAIL PROTECTED]
----
For more information on Real-Time Linux see:
http://www.rtlinux.org/~rtlinux/
