On Thu, May 03, 2012 at 10:41:22PM -0700, Guenter Roeck wrote:
> 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.
Without kref, what prevents following situation:
CPU-A CPU-B
tdata = get_temp_data();
coretemp_remove_core() {
device_remove_file();
kfree(tdata);
}
<tdata dereference>
?
--
Kirill A. Shutemov
Attachment:
signature.asc
Description: Digital signature
_______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
