Messages in this thread | | | Date | Sat, 26 Sep 2015 13:56:22 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH v2 5/7] x86, acpi, cpu-hotplug: Introduce apicid_to_cpuid[] array to store persistent cpuid <-> apicid mapping. |
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On Sat, Sep 26, 2015 at 05:52:09PM +0800, Tang Chen wrote: > >>+static int allocate_logical_cpuid(int apicid) > >>+{ > >>+ int i; > >>+ > >>+ /* > >>+ * cpuid <-> apicid mapping is persistent, so when a cpu is up, > >>+ * check if the kernel has allocated a cpuid for it. > >>+ */ > >>+ for (i = 0; i < max_logical_cpuid; i++) { > >>+ if (cpuid_to_apicid[i] == apicid) > >>+ return i; > >>+ } > >>+ > >>+ /* Allocate a new cpuid. */ > >>+ if (max_logical_cpuid >= nr_cpu_ids) { > >>+ WARN_ONCE(1, "Only %d processors supported." > >>+ "Processor %d/0x%x and the rest are ignored.\n", > >>+ nr_cpu_ids - 1, max_logical_cpuid, apicid); > >>+ return -1; > >>+ } > >So, the original code didn't have this failure mode, why is this > >different for the new code? > > It is not different. Since max_logical_cpuid is new, this is ensure it won't > go beyond NR_CPUS.
If the above condition can happen, the original code should have had a similar check as above, right? Sure, max_logical_cpuid is a new thing but that doesn't seem to change whether the above condition can happen or not, no?
Thanks.
-- tejun
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