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]
