From f4e0bcf06b9771af04273473592aeeb860ca2816 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Mon, 23 May 2011 14:05:38 -0700 Subject: hwmon: (coretemp) Add comments describing the handling of HT CPUs 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 d883b9f09772 ("hwmon: (coretemp) Skip duplicate CPU entries"). Commit e40cc4bdfd4b ("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 Cc: Fenghua Yu Cc: Durgadoss R Signed-off-by: Linus Torvalds --- drivers/hwmon/coretemp.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) (limited to 'drivers/hwmon') diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c index a00245eb3fa0..9577c432e77f 100644 --- a/drivers/hwmon/coretemp.c +++ b/drivers/hwmon/coretemp.c @@ -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; } } -- cgit v1.2.3