Messages in this thread | | | From | "Manfred Spraul" <> | Subject | Re: softirq buggy [Re: Serial port latency] | Date | Sun, 8 Apr 2001 20:16:49 +0200 |
| |
From: <kuznet@ms2.inr.ac.ru> To: "Manfred Spraul" <manfred@colorfullife.com> Cc: <linux-kernel@vger.redhat.com> Sent: Sunday, April 08, 2001 7:58 PM Subject: Re: softirq buggy [Re: Serial port latency]
> Hello! > > > But with a huge overhead. I'd prefer to call it directly from within the > > idle functions, the overhead of schedule is IMHO too high. > > > + if (current->need_resched) { > + return 0; > ^^^^^^^^ > + } > + if (softirq_active(smp_processor_id()) & softirq_mask(smp_processor_id())) { > + do_softirq(); > + return 0; > ^^^^^^^^^ > You return one value in both casesand I decided it means "schedule". 8) > Apparently you meaned return 1 in the first case. 8) > No, the code is correct. 0 means "don't stop the cpu". The pm_idle function pointer will return to cpu_idle() (arch/i386/kernel/process.c), and that function contains another
while(!current->need_resched) idle();
loop ;-)
> But in this case it becomes wrong. do_softirq() can raise need_reshed > and moreover irqs arrive during it. Order of check should be different. > Yes, I'll correct that.
> > BTW what's about overhead... I suspect it is _lower_ in the case > of schedule(). In the case of networking at least, when softirq > most likely wakes some socket. > I'm not sure - what if the computer is just a router? But OTHO: the cpu is idle, so it doesn't matter at all if the idle cpu spends it's time within schedule() or within safe_hlt(), I'll change my patch.
I have another question: I added cpu_is_idle() into <linux/interrupt.h>. Is that acceptable, or is there a better header file for such a function?
-- Manfred
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |