cpumask: add cpumask_var_t documentation

a64a26e8 · KOSAKI Motohiro <[email protected]> · 2011-07-26 16:08:45 -07:00

cpumask_var_t has one notable difference from cpumask_t.  Add the
explanation.

Signed-off-by: KOSAKI Motohiro <[email protected]>
Cc: Thiago Farina <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: a64a26e822ddb739de464540dfd2cbb6abce47d5
Parents: 37e7b5f1

Changes

1 files changed · +14 −0

File	Status	Add	Del	Content
include/linux/cpumask.h	modified	+14	−0	View file

include/linux/cpumask.h

View file

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index b24ac56..4f7a632 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -617,6 +617,20 @@ static inline size_t cpumask_size(void)
  *	  ... use 'tmpmask' like a normal struct cpumask * ...
  *
  *	free_cpumask_var(tmpmask);
+ *
+ *
+ * However, one notable exception is there. alloc_cpumask_var() allocates
+ * only nr_cpumask_bits bits (in the other hand, real cpumask_t always has
+ * NR_CPUS bits). Therefore you don't have to dereference cpumask_var_t.
+ *
+ *	cpumask_var_t tmpmask;
+ *	if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL))
+ *		return -ENOMEM;
+ *
+ *	var = *tmpmask;
+ *
+ * This code makes NR_CPUS length memcopy and brings to a memory corruption.
+ * cpumask_copy() provide safe copy functionality.
  */
 #ifdef CONFIG_CPUMASK_OFFSTACK
 typedef struct cpumask *cpumask_var_t;