2009/3/16 Matthias Kaehlcke <matthias@xxxxxxxxxxxx>: > El Mon, Mar 16, 2009 at 01:03:35PM +0300 Denis Borisevich ha dit: > >> 2009/3/16 Razvan Deaconescu <razvan@xxxxxxxxxxxxxxxxxx>: >> > On Mon, 2009-03-16 at 00:41 +0300, Denis Borisevich wrote: >> >> Hi! >> >> Is there any way to achieve a timeout of say 10 usecs in kernel module? >> > >> > See udelay[1]. Please note that it does busy-waiting (you can't >> > block/put to sleep the current process for periods less than 1000/HZ >> > milliseconds). >> > >> > Razvan >> > >> > [1] http://lxr.linux.no/linux+v2.6.28.7/arch/x86/include/asm/delay.h#20 >> >> >> Hmm..busy-wait is not good for my situation. Is there any way to >> achieve these little timeouts with RT_PREEMPT patch? > > user space processes can use nanosleep() for sleeping for short times, > though the kernel only guarantees that the process will sleep *at > least* the specified time. the implementation of nanosleep() uses > hrtimer_nanosleep() to achieve this, maybe you could try something > similar: > > http://lxr.linux.no/linux+v2.6.28/kernel/hrtimer.c#L1632 > > 10 usecs is a very short time for sleeping, i'm not sure if the kernel > can provide this granularity. probably your task needs to have rt > priority to be re-scheduled after such a short period. > > ftrace (Documentation/ftrace.txt) can be useful to determine whether > the real sleep time is near to the period you pretend. > > -- > Matthias Kaehlcke > Embedded Linux Engineer > Barcelona > > > Someone has said that it requires less mental effort to condemn than to think > (Emma Goldman) > .''`. > using free software / Debian GNU/Linux | http://debian.org : :' : > `. `'` > gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `- > In our project we use rt-enabled kernel. And the application's main working loop is about 2ms that's why I need such little timeouts in my driver. Thank you for your help. I will look at hr-timers usage. -- Denis -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
