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-rw-r--r--include/linux/cpumask.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 2997af6d2ccd..0a9a6da21e74 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -666,10 +666,19 @@ static inline size_t cpumask_size(void)
*
* This code makes NR_CPUS length memcopy and brings to a memory corruption.
* cpumask_copy() provide safe copy functionality.
+ *
+ * Note that there is another evil here: If you define a cpumask_var_t
+ * as a percpu variable then the way to obtain the address of the cpumask
+ * structure differently influences what this_cpu_* operation needs to be
+ * used. Please use this_cpu_cpumask_var_t in those cases. The direct use
+ * of this_cpu_ptr() or this_cpu_read() will lead to failures when the
+ * other type of cpumask_var_t implementation is configured.
*/
#ifdef CONFIG_CPUMASK_OFFSTACK
typedef struct cpumask *cpumask_var_t;
+#define this_cpu_cpumask_var_ptr(x) this_cpu_read(x)
+
bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node);
bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags);
bool zalloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node);
@@ -681,6 +690,8 @@ void free_bootmem_cpumask_var(cpumask_var_t mask);
#else
typedef struct cpumask cpumask_var_t[1];
+#define this_cpu_cpumask_var_ptr(x) this_cpu_ptr(x)
+
static inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
{
return true;