On Fri, Dec 09, 2005 at 14:37:49 +0200, MHD.Tayseer wrote: > Hsieh Steve wrote: > > >Hi , everybody > > I've got some problem about kernel thread and hope some one give > >me some hint. > > 1) is kernel thread a real-time process? > > No .. acctualy , being a real-time or non-real-time task is a diferent > issue from being a process/thread ... this means you can use the call > "sched_setscheduler(2)" to change the scheduling algorithms to meet > real-time constrains, and changing the scheduling algorithm can be > applied to both proceses and kernel threads .. > AFAIK, the difference between process and thread in linux is subtle .. > they are almost the same but what make them different is that the > process has a separate memory allocated for it while the thread is a > process that it's memory is a pointer to it's parent process > > > 2) is there any difference between the scheduling of kernel > >thread and that of user process?? > > > kernel is unaware of the user-level threads .. this means that it's not It depends on what you call a "user-level" thread. Threads created with pthreads *ARE* scheduled by kernel. All schedulable entities are the same as far as scheduler is concerned (ok, they can use different scheduling algorithm (real-time/normal)). > responsible of scheduling them, scheduling user-level threads is done by > the thread library, while scheduling kernel-level threads is a kernel > responsibility kernel-level threads and kernel threads are two vastly different things. kernel-level thread (usually) means: A thread of a user space application, that is a schedulable entity. kernel thread means: A schedulable entity that runs kernel space code and has no associated user space. > this makes the 3 kernel-level threads able of doing 3 blocking calls > while user-level threads are not .. cause calling a blocking operation > from a user-level thread will end to blocking the whole process owning them Right, but I believe the question was about the kernel threads, NOT kernel-level (user space) threads. -- Jan 'Bulb' Hudec <bulb@xxxxxx>
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