Messages in this thread | | | Date | Tue, 09 Nov 2004 09:54:56 -0500 | From | Mike Waychison <> | Subject | Re: problem with printk on SMP-- somebody please help |
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Arun Srinivas wrote: > hi > > I really appreciate your suggestions and as a newcomer eager to learn > more from you people. > > As I said I was able to do printk anywhere in the sched.c (including > _activate_task ) on a non-smp kernel and on a smp-kernel I can do it > only on the main schedule() function. > Also, I would like to add that I am not able to do the macro rdtsc() for > reading the timestamp counter in the same function.When I compile the > kernel it dosent show any error, but just the printk's and rdtsc()'s get > subdued! > > Well, with reference to your reply, I have some basic questions: > 1) on a non-smp kernel will the _activate_task not lock the given runqueue?
The locking is done in schedule(). Read include/linux/spinlock.h to see how spinlocks differ in the SMP vs non-SMP case. In the latter case with spinlock debugging enabled, there is no lock bit and recursively grabbing a lock is possible (though still not allowed!).
> 2) where is the best place I can do the rdtsc() and printk to read the > value as to when a task is being scheduled for execution, on a SMP kernel? >
No idea wrt to rdtsc.
HTH,
- -- Mike Waychison Sun Microsystems, Inc. 1 (650) 352-5299 voice 1 (416) 202-8336 voice
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