Hi tglx,
在 2016年07月29日 21:36, Thomas Gleixner 写道:
On Tue, 26 Jul 2016, Dou Liyang wrote:
1. Enable apic registeration flow to handle both enabled and disabled cpus.
This is done by introducing an extra parameter to generic_processor_info to
let the caller control if disabled cpus are ignored.
If I'm reading the patch correctly then the 'enabled' argument controls more
than the disabled cpus accounting. It also controls the modification of
num_processors and the present mask.
In the patch, they both need mapping to a logic cpu.
As you said, the 'enabled' controls extra functions:
1. num_processors parameter
2. physid_set method
3. set_cpu_present method
-int generic_processor_info(int apicid, int version)
+static int __generic_processor_info(int apicid, int version, bool enabled)
{
int cpu, max = nr_cpu_ids;
bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
@@ -2032,7 +2032,8 @@ int generic_processor_info(int apicid, int version)
" Processor %d/0x%x ignored.\n",
thiscpu, apicid);
- disabled_cpus++;
+ if (enabled)
+ disabled_cpus++;
return -ENODEV;
}
@@ -2049,7 +2050,8 @@ int generic_processor_info(int apicid, int version)
" reached. Keeping one slot for boot cpu."
" Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
- disabled_cpus++;
+ if (enabled)
+ disabled_cpus++;
This is utterly confusing. That code path cannot be reached when enabled is
false, because num_processors is 0 as we never increment it when enabled is
false.
That said, I really do not like this 'slap some argument on it and make it
work somehow' approach.
The proper solution for this is to seperate out the functionality which you
need for the preparation run (enabled = false) and make sure that the
information you need for the real run (enabled = true) is properly cached
somewhere so we don't have to evaluate the same thing over and over.
Thank you very much for your advice. That solution is very good for me.
I thought about the differences between them carefully. Firstly, I
intend to separate out the functionality in two functions. It's simple
but not good. Then, I try to put them together to judge just once.
After, considering the judgment statement independence and the order of
assignment. I remove all the "if (enabled)" code and do the unified
judgment like this:
@@ -2180,12 +2176,19 @@ int __generic_processor_info(int apicid, int
version, bool enabled)
apic->x86_32_early_logical_apicid(cpu);
#endif
set_cpu_possible(cpu, true);
- if (enabled)
+
+ if (enabled){
+ num_processors++;
+ physid_set(apicid, phys_cpu_present_map);
set_cpu_present(cpu, true);
+ }else{
+ disabled_cpus++;
+ }
return cpu;
}
I hope that patch could consistent with your advice. And I will submit
the detailed modification in the next version patches.
Thanks,
Dou.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>