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hwmon: (coretemp) Add comments describing the handling of HT CPUs

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The coretemp driver provides a single set of device attributes for each
physical core of a HT CPU to avoid duplicate sensors.  This
functionality was introduced with commit d883b9f097 ("hwmon:
(coretemp) Skip duplicate CPU entries").

Commit e40cc4bdfd ("x86/hwmon: register alternate sibling upon CPU
removal") extends this functionality to register the HT sibling of a CPU
which is taken offline, to ensure that sensor attributes are provided if
at least one HT sibling of a core is online.

Add comments into the code describing the functionality in some more
detail.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Guenter Roeck 2011-05-23 14:05:38 -07:00 committed by Linus Torvalds
parent 5f2e8e2b0b
commit f4e0bcf06b
1 changed files with 18 additions and 2 deletions
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20
drivers/hwmon/coretemp.c
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@ -506,7 +506,13 @@ static int create_core_data(struct platform_data *pdata,
if (attr_no > MAX_CORE_DATA - 1)
return -ERANGE;
/* Skip if it is a HT core, Not an error */
/*
* Provide a single set of attributes for all HT siblings of a core
* to avoid duplicate sensors (the processor ID and core ID of all
* HT siblings of a core is the same).
* Skip if a HT sibling of this core is already online.
* This is not an error.
*/
if (pdata->core_data[attr_no] != NULL)
return 0;
@ -763,10 +769,20 @@ static void __cpuinit put_core_offline(unsigned int cpu)
if (pdata->core_data[indx] && pdata->core_data[indx]->cpu == cpu)
coretemp_remove_core(pdata, &pdev->dev, indx);
/* Online the HT version of this core, if any */
/*
* If a core is taken offline, but a HT sibling of the same core is
* still online, register the alternate sibling. This ensures that
* exactly one set of attributes is provided as long as at least one
* HT sibling of a core is online.
*/
for_each_sibling(i, cpu) {
if (i != cpu) {
get_core_online(i);
/*
* Display temperature sensor data for one HT sibling
* per core only, so abort the loop after one such
* sibling has been found.
*/
break;
}
}