On 09/27/2015 01:56 AM, Tejun Heo wrote:
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?
Right, indeed. It is in
generic_processor_info()
|--> if (num_processors >= nr_cpu_ids)
Will remove my new added check.
Thanks.
Thanks.
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