Re: [RFC PATCH] Dynamic sched domains (v0.5)

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Dinakar Guniguntala wrote:
On Mon, May 02, 2005 at 07:44:05PM +1000, Nick Piggin wrote:

Dinakar Guniguntala wrote:


+void rebuild_sched_domains(cpumask_t span1, cpumask_t span2)
+{
+	cpumask_t change_map;
+
+	cpus_or(change_map, span1, span2);
+
+	preempt_disable();

Oh, you can't do this here, attach_domains does a synchronize_kernel.
So take it out, it doesn't do anything anyway, does it?


I put that in to prevent hangs with CONFIG_PREEMPT turned on, but
clearly didn't test it with preempt turned on. Looks like all I need to do here is a local_irq_disable


What are you protecting against, though? synchroinze_kernel can
sleep, so local_irq_disable is probably the wrong thing to do as well.

AFAIKS, you don't need anything here - so long as you have mutual
exclusion from other sched-domain building then this can take as long
as it wants / be preempted as many times as we like.


I suggest you also use some sort of locking to prevent concurrent rebuilds
and rebuilds racing with cpu hotplug. You could probably have a static
semaphore around rebuild_sched_domains, and take lock_cpu_hotplug here too.


I already do a lock_cpu_hotplug() in cpuset.c before calling rebuild_sched_domains and also am holding cpuset_sem, so that should take
care of both hotplug and concurrent rebuilds


OK.

But if we want this to be a respectable interface (possibly for more than
just cpusets) then it should probably do some locking itself. It isn't
performance critical, so I think taking a semaphore wouldn't hurt.

--
SUSE Labs, Novell Inc.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux