Messages in this thread | | | Date | Thu, 18 Oct 2007 13:27:02 +0530 | From | Gautham R Shenoy <> | Subject | Re: [RFC PATCH 2/4] Rename lock_cpu_hotplug to get_online_cpus |
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Hi Nathan, > Hi Gautham- > > Gautham R Shenoy wrote: > > Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use > > get_online_cpus and put_online_cpus instead as it highlights > > the refcount semantics in these operations. > > Something other than "get_online_cpus", please? lock_cpu_hotplug() > protects cpu_present_map as well as cpu_online_map. For example, some > of the powerpc code modified in this patch is made a bit less clear > because it is manipulating cpu_present_map, not cpu_online_map.
A quick look at the code, and I am wondering why is lock_cpu_hotplug() used there in the first place. It doesn't look like we require any protection against cpus coming up/ going down in the code below, since the cpu-hotplug operation doesn't affect the cpu_present_map.
Can't we use another mutex here instead of the cpu_hotplug mutex here ?
> > > > Index: linux-2.6.23/arch/powerpc/platforms/pseries/hotplug-cpu.c > > =================================================================== > > --- linux-2.6.23.orig/arch/powerpc/platforms/pseries/hotplug-cpu.c > > +++ linux-2.6.23/arch/powerpc/platforms/pseries/hotplug-cpu.c > > @@ -151,7 +151,7 @@ static int pseries_add_processor(struct > > for (i = 0; i < nthreads; i++) > > cpu_set(i, tmp); > > > > - lock_cpu_hotplug(); > > + get_online_cpus(); > > > > BUG_ON(!cpus_subset(cpu_present_map, cpu_possible_map)); > > > > @@ -188,7 +188,7 @@ static int pseries_add_processor(struct > > } > > err = 0; > > out_unlock: > > - unlock_cpu_hotplug(); > > + put_online_cpus(); > > return err; > > } > > > > @@ -209,7 +209,7 @@ static void pseries_remove_processor(str > > > > nthreads = len / sizeof(u32); > > > > - lock_cpu_hotplug(); > > + get_online_cpus(); > > for (i = 0; i < nthreads; i++) { > > for_each_present_cpu(cpu) { > > if (get_hard_smp_processor_id(cpu) != intserv[i]) > > @@ -223,7 +223,7 @@ static void pseries_remove_processor(str > > printk(KERN_WARNING "Could not find cpu to remove " > > "with physical id 0x%x\n", intserv[i]); > > } > > - unlock_cpu_hotplug(); > > + put_online_cpus(); > > }
-- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!" - 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/
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