Re: [PATCH, v2] hwmon: coretemp: use list instead of fixed sizearray for temp data

[Guenter Roeck]

On Thu, May 03, 2012 at 07:18:56AM -0400, Kirill A. Shutemov wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> 
> Let's rework code to allow arbitrary number of cores on a CPU, not
> limited by hardcoded array size.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> ---
>  v2:
>    - fix NULL pointer dereference. Thanks to R, Durgadoss;
>    - use mutex instead of spinlock for list locking.
> ---
>  drivers/hwmon/coretemp.c |  178 +++++++++++++++++++++++++++++++++-------------
>  1 files changed, 129 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index 54a70fe..1c66131 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -36,6 +36,8 @@
>  #include <linux/cpu.h>
>  #include <linux/pci.h>
>  #include <linux/smp.h>
> +#include <linux/list.h>
> +#include <linux/kref.h>
>  #include <linux/moduleparam.h>
>  #include <asm/msr.h>
>  #include <asm/processor.h>
> @@ -52,11 +54,9 @@ module_param_named(tjmax, force_tjmax, int, 0444);
>  MODULE_PARM_DESC(tjmax, "TjMax value in degrees Celsius");
> 
>  #define BASE_SYSFS_ATTR_NO     2       /* Sysfs Base attr no for coretemp */
> -#define NUM_REAL_CORES         16      /* Number of Real cores per cpu */
>  #define CORETEMP_NAME_LENGTH   17      /* String Length of attrs */
>  #define MAX_CORE_ATTRS         4       /* Maximum no of basic attrs */
>  #define TOTAL_ATTRS            (MAX_CORE_ATTRS + 1)
> -#define MAX_CORE_DATA          (NUM_REAL_CORES + BASE_SYSFS_ATTR_NO)
> 
>  #define TO_PHYS_ID(cpu)                (cpu_data(cpu).phys_proc_id)
>  #define TO_CORE_ID(cpu)                (cpu_data(cpu).cpu_core_id)
> @@ -82,6 +82,9 @@ MODULE_PARM_DESC(tjmax, "TjMax value in degrees Celsius");
>   * @valid: If this is 1, the current temperature is valid.
>   */
>  struct temp_data {
> +       struct list_head list;
> +       struct kref refcount;

Hi,

the kref is not needed. The attribute access functions don't
need to be protected since the attributes for a core are deleted
before the core data itself is deleted. So it is not neccessary 
to hold a lock while accessing/using temp_data in the attribute
access functions. All you need is to hold a mutex while you are
manipulating or walking the list.

Thanks,
Guenter

> +       int id;
>         int temp;
>         int ttarget;
>         int tjmax;
> @@ -101,7 +104,8 @@ struct temp_data {
>  struct platform_data {
>         struct device *hwmon_dev;
>         u16 phys_proc_id;
> -       struct temp_data *core_data[MAX_CORE_DATA];
> +       struct list_head temp_data_list;
> +       struct mutex temp_data_lock;
>         struct device_attribute name_attr;
>  };
> 
> @@ -114,6 +118,29 @@ struct pdev_entry {
>  static LIST_HEAD(pdev_list);
>  static DEFINE_MUTEX(pdev_list_mutex);
> 
> +static void temp_data_release(struct kref *ref)
> +{
> +       struct temp_data *tdata = container_of(ref, struct temp_data, refcount);
> +
> +       kfree(tdata);
> +}
> +
> +static struct temp_data *get_temp_data(struct platform_data *pdata, int id)
> +{
> +       struct temp_data *tdata;
> +
> +       mutex_lock(&pdata->temp_data_lock);
> +       list_for_each_entry(tdata, &pdata->temp_data_list, list)
> +               if (tdata->id == id) {
> +                       kref_get(&tdata->refcount);
> +                       goto out;
> +               }
> +       tdata = NULL;
> +out:
> +       mutex_unlock(&pdata->temp_data_lock);
> +       return tdata;
> +}
> +
>  static ssize_t show_name(struct device *dev,
>                         struct device_attribute *devattr, char *buf)
>  {
> @@ -125,12 +152,19 @@ static ssize_t show_label(struct device *dev,
>  {
>         struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
>         struct platform_data *pdata = dev_get_drvdata(dev);
> -       struct temp_data *tdata = pdata->core_data[attr->index];
> +       struct temp_data *tdata = get_temp_data(pdata, attr->index);
> +       ssize_t ret;
> +
> +       if (!tdata)
> +               return -ENOENT;
> 
>         if (tdata->is_pkg_data)
> -               return sprintf(buf, "Physical id %u\n", pdata->phys_proc_id);
> +               ret = sprintf(buf, "Physical id %u\n", pdata->phys_proc_id);
> +       else
> +               ret = sprintf(buf, "Core %u\n", tdata->cpu_core_id);
> 
> -       return sprintf(buf, "Core %u\n", tdata->cpu_core_id);
> +       kref_put(&tdata->refcount, temp_data_release);
> +       return ret;
>  }
> 
>  static ssize_t show_crit_alarm(struct device *dev,
> @@ -139,11 +173,18 @@ static ssize_t show_crit_alarm(struct device *dev,
>         u32 eax, edx;
>         struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
>         struct platform_data *pdata = dev_get_drvdata(dev);
> -       struct temp_data *tdata = pdata->core_data[attr->index];
> +       struct temp_data *tdata = get_temp_data(pdata, attr->index);
> +       ssize_t ret;
> +
> +       if (!tdata)
> +               return -ENOENT;
> 
>         rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
> 
> -       return sprintf(buf, "%d\n", (eax >> 5) & 1);
> +       ret = sprintf(buf, "%d\n", (eax >> 5) & 1);
> +
> +       kref_put(&tdata->refcount, temp_data_release);
> +       return ret;
>  }
> 
>  static ssize_t show_tjmax(struct device *dev,
> @@ -151,8 +192,16 @@ static ssize_t show_tjmax(struct device *dev,
>  {
>         struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
>         struct platform_data *pdata = dev_get_drvdata(dev);
> +       struct temp_data *tdata = get_temp_data(pdata, attr->index);
> +       ssize_t ret;
> +
> +       if (!tdata)
> +               return -ENOENT;
> +
> +       ret = sprintf(buf, "%d\n", tdata->tjmax);
> 
> -       return sprintf(buf, "%d\n", pdata->core_data[attr->index]->tjmax);
> +       kref_put(&tdata->refcount, temp_data_release);
> +       return ret;
>  }
> 
>  static ssize_t show_ttarget(struct device *dev,
> @@ -160,8 +209,16 @@ static ssize_t show_ttarget(struct device *dev,
>  {
>         struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
>         struct platform_data *pdata = dev_get_drvdata(dev);
> +       struct temp_data *tdata = get_temp_data(pdata, attr->index);
> +       ssize_t ret;
> 
> -       return sprintf(buf, "%d\n", pdata->core_data[attr->index]->ttarget);
> +       if (!tdata)
> +               return -ENOENT;
> +
> +       ret = sprintf(buf, "%d\n", tdata->ttarget);
> +
> +       kref_put(&tdata->refcount, temp_data_release);
> +       return ret;
>  }
> 
>  static ssize_t show_temp(struct device *dev,
> @@ -170,7 +227,11 @@ static ssize_t show_temp(struct device *dev,
>         u32 eax, edx;
>         struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
>         struct platform_data *pdata = dev_get_drvdata(dev);
> -       struct temp_data *tdata = pdata->core_data[attr->index];
> +       struct temp_data *tdata = get_temp_data(pdata, attr->index);
> +       ssize_t ret = -EAGAIN;
> +
> +       if (!tdata)
> +               return -ENOENT;
> 
>         mutex_lock(&tdata->update_lock);
> 
> @@ -188,7 +249,12 @@ static ssize_t show_temp(struct device *dev,
>         }
> 
>         mutex_unlock(&tdata->update_lock);
> -       return tdata->valid ? sprintf(buf, "%d\n", tdata->temp) : -EAGAIN;
> +
> +       if (tdata->valid)
> +               ret = sprintf(buf, "%d\n", tdata->temp);
> +
> +       kref_put(&tdata->refcount, temp_data_release);
> +       return ret;
>  }
> 
>  static int __cpuinit adjust_tjmax(struct cpuinfo_x86 *c, u32 id,
> @@ -412,6 +478,7 @@ static struct temp_data __cpuinit *init_temp_data(unsigned int cpu,
>         tdata = kzalloc(sizeof(struct temp_data), GFP_KERNEL);
>         if (!tdata)
>                 return NULL;
> +       kref_init(&tdata->refcount);
> 
>         tdata->status_reg = pkg_flag ? MSR_IA32_PACKAGE_THERM_STATUS :
>                                                         MSR_IA32_THERM_STATUS;
> @@ -423,7 +490,7 @@ static struct temp_data __cpuinit *init_temp_data(unsigned int cpu,
>         return tdata;
>  }
> 
> -static int __cpuinit create_core_data(struct platform_device *pdev,
> +static int __cpuinit create_temp_data(struct platform_device *pdev,
>                                 unsigned int cpu, int pkg_flag)
>  {
>         struct temp_data *tdata;
> @@ -440,9 +507,6 @@ static int __cpuinit create_core_data(struct platform_device *pdev,
>          */
>         attr_no = pkg_flag ? 1 : TO_ATTR_NO(cpu);
> 
> -       if (attr_no > MAX_CORE_DATA - 1)
> -               return -ERANGE;
> -
>         /*
>          * 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
> @@ -450,8 +514,14 @@ static int __cpuinit create_core_data(struct platform_device *pdev,
>          * Skip if a HT sibling of this core is already registered.
>          * This is not an error.
>          */
> -       if (pdata->core_data[attr_no] != NULL)
> -               return 0;
> +       mutex_lock(&pdata->temp_data_lock);
> +       list_for_each_entry(tdata, &pdata->temp_data_list, list) {
> +               if (tdata->id == attr_no) {
> +                       mutex_unlock(&pdata->temp_data_lock);
> +                       return 0;
> +               }
> +       }
> +       mutex_unlock(&pdata->temp_data_lock);
> 
>         tdata = init_temp_data(cpu, pkg_flag);
>         if (!tdata)
> @@ -480,16 +550,23 @@ static int __cpuinit create_core_data(struct platform_device *pdev,
>                 }
>         }
> 
> -       pdata->core_data[attr_no] = tdata;
> +       tdata->id = attr_no;
> +
> +       mutex_lock(&pdata->temp_data_lock);
> +       list_add(&tdata->list, &pdata->temp_data_list);
> +       mutex_unlock(&pdata->temp_data_lock);
> 
>         /* Create sysfs interfaces */
>         err = create_core_attrs(tdata, &pdev->dev, attr_no);
>         if (err)
> -               goto exit_free;
> +               goto exit_list_del;
> 
>         return 0;
> +exit_list_del:
> +       mutex_lock(&pdata->temp_data_lock);
> +       list_del(&tdata->list);
> +       mutex_unlock(&pdata->temp_data_lock);
>  exit_free:
> -       pdata->core_data[attr_no] = NULL;
>         kfree(tdata);
>         return err;
>  }
> @@ -502,23 +579,21 @@ static void __cpuinit coretemp_add_core(unsigned int cpu, int pkg_flag)
>         if (!pdev)
>                 return;
> 
> -       err = create_core_data(pdev, cpu, pkg_flag);
> +       err = create_temp_data(pdev, cpu, pkg_flag);
>         if (err)
>                 dev_err(&pdev->dev, "Adding Core %u failed\n", cpu);
>  }
> 
> -static void coretemp_remove_core(struct platform_data *pdata,
> -                               struct device *dev, int indx)
> +static void coretemp_remove_core(struct temp_data *tdata, struct device *dev)
>  {
>         int i;
> -       struct temp_data *tdata = pdata->core_data[indx];
> 
>         /* Remove the sysfs attributes */
>         for (i = 0; i < tdata->attr_size; i++)
>                 device_remove_file(dev, &tdata->sd_attrs[i].dev_attr);
> 
> -       kfree(pdata->core_data[indx]);
> -       pdata->core_data[indx] = NULL;
> +       list_del(&tdata->list);
> +       kref_put(&tdata->refcount, temp_data_release);
>  }
> 
>  static int __devinit coretemp_probe(struct platform_device *pdev)
> @@ -536,6 +611,8 @@ static int __devinit coretemp_probe(struct platform_device *pdev)
>                 goto exit_free;
> 
>         pdata->phys_proc_id = pdev->id;
> +       INIT_LIST_HEAD(&pdata->temp_data_list);
> +       mutex_init(&pdata->temp_data_lock);
>         platform_set_drvdata(pdev, pdata);
> 
>         pdata->hwmon_dev = hwmon_device_register(&pdev->dev);
> @@ -557,11 +634,12 @@ exit_free:
>  static int __devexit coretemp_remove(struct platform_device *pdev)
>  {
>         struct platform_data *pdata = platform_get_drvdata(pdev);
> -       int i;
> +       struct temp_data *cur, *tmp;
> 
> -       for (i = MAX_CORE_DATA - 1; i >= 0; --i)
> -               if (pdata->core_data[i])
> -                       coretemp_remove_core(pdata, &pdev->dev, i);
> +       mutex_lock(&pdata->temp_data_lock);
> +       list_for_each_entry_safe(cur, tmp, &pdata->temp_data_list, list)
> +               coretemp_remove_core(cur, &pdev->dev);
> +       mutex_unlock(&pdata->temp_data_lock);
> 
>         device_remove_file(&pdev->dev, &pdata->name_attr);
>         hwmon_device_unregister(pdata->hwmon_dev);
> @@ -641,16 +719,17 @@ static void __cpuinit coretemp_device_remove(unsigned int cpu)
> 
>  static bool __cpuinit is_any_core_online(struct platform_data *pdata)
>  {
> -       int i;
> -
> -       /* Find online cores, except pkgtemp data */
> -       for (i = MAX_CORE_DATA - 1; i >= 0; --i) {
> -               if (pdata->core_data[i] &&
> -                       !pdata->core_data[i]->is_pkg_data) {
> -                       return true;
> -               }
> -       }
> -       return false;
> +       struct temp_data *tdata;
> +       bool ret = true;
> +
> +       mutex_lock(&pdata->temp_data_lock);
> +       list_for_each_entry(tdata, &pdata->temp_data_list, list)
> +               if (!tdata->is_pkg_data)
> +                        goto out;
> +       ret = false;
> +out:
> +       mutex_unlock(&pdata->temp_data_lock);
> +       return ret;
>  }
> 
>  static void __cpuinit get_core_online(unsigned int cpu)
> @@ -697,9 +776,10 @@ static void __cpuinit get_core_online(unsigned int cpu)
> 
>  static void __cpuinit put_core_offline(unsigned int cpu)
>  {
> -       int i, indx;
> +       int i, attr_no;
>         struct platform_data *pdata;
>         struct platform_device *pdev = coretemp_get_pdev(cpu);
> +       struct temp_data *tdata;
> 
>         /* If the physical CPU device does not exist, just return */
>         if (!pdev)
> @@ -707,14 +787,14 @@ static void __cpuinit put_core_offline(unsigned int cpu)
> 
>         pdata = platform_get_drvdata(pdev);
> 
> -       indx = TO_ATTR_NO(cpu);
> +       attr_no = TO_ATTR_NO(cpu);
> 
> -       /* The core id is too big, just return */
> -       if (indx > MAX_CORE_DATA - 1)
> -               return;
> -
> -       if (pdata->core_data[indx] && pdata->core_data[indx]->cpu == cpu)
> -               coretemp_remove_core(pdata, &pdev->dev, indx);
> +       tdata = get_temp_data(pdata, attr_no);
> +       if (tdata) {
> +               if (tdata->cpu == cpu)
> +                       coretemp_remove_core(tdata, &pdev->dev);
> +               kref_put(&tdata->refcount, temp_data_release);
> +       }
> 
>         /*
>          * If a HT sibling of a core is taken offline, but another HT sibling
> --
> 1.7.9.1
> 
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