From a64a26e822ddb739de464540dfd2cbb6abce47d5 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Tue, 26 Jul 2011 16:08:45 -0700 Subject: [PATCH] cpumask: add cpumask_var_t documentation cpumask_var_t has one notable difference from cpumask_t. Add the explanation. Signed-off-by: KOSAKI Motohiro Cc: Thiago Farina Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cpumask.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index b24ac56477b4..4f7a63237471 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; -- 2.20.1