[PATCH v2 1/2] cpumask: Add helper cpumask_available()

* [PATCH v2 1/2] cpumask: Add helper cpumask_available()
@ 2017-04-12 18:20 Matthias Kaehlcke
  2017-04-12 18:20 ` [PATCH v2 2/2] kernel/irq: Use cpumask_available() for check of cpumask variable Matthias Kaehlcke
  2017-04-14 17:54 ` [tip:irq/core] cpumask: Add helper cpumask_available() tip-bot for Matthias Kaehlcke
  0 siblings, 2 replies; 6+ messages in thread
From: Matthias Kaehlcke @ 2017-04-12 18:20 UTC (permalink / raw)
  To: Thomas Gleixner, Andrew Morton, Rusty Russell
  Cc: linux-kernel, Grant Grundler, Greg Hackmann, Michael Davidson,
	Matthias Kaehlcke

With CONFIG_CPUMASK_OFFSTACK=y cpumask_var_t is a struct cpumask
pointer, otherwise a struct cpumask array with a single element.

Some code dealing with cpumasks needs to validate that a cpumask_var_t
is not a NULL pointer when CONFIG_CPUMASK_OFFSTACK=y. This is typically
done by performing the check always, regardless of the underlying type
of cpumask_var_t. This works in both cases, however clang raises a
warning like this when CONFIG_CPUMASK_OFFSTACK=n:

kernel/irq/manage.c:839:28: error: address of array
'desc->irq_common_data.affinity' will always evaluate to 'true'
[-Werror,-Wpointer-bool-conversion]

Add the inline helper cpumask_available() which only performs the
pointer check if CONFIG_CPUMASK_OFFSTACK=y.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
Changes in v2:
- Patch added

 include/linux/cpumask.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 96f1e88b767c..1a675604b17d 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -667,6 +667,11 @@ void alloc_bootmem_cpumask_var(cpumask_var_t *mask);
 void free_cpumask_var(cpumask_var_t mask);
 void free_bootmem_cpumask_var(cpumask_var_t mask);
 
+static inline bool cpumask_available(cpumask_var_t mask)
+{
+	return mask != NULL;
+}
+
 #else
 typedef struct cpumask cpumask_var_t[1];
 
@@ -708,6 +713,11 @@ static inline void free_cpumask_var(cpumask_var_t mask)
 static inline void free_bootmem_cpumask_var(cpumask_var_t mask)
 {
 }
+
+static inline bool cpumask_available(cpumask_var_t mask)
+{
+	return true;
+}
 #endif /* CONFIG_CPUMASK_OFFSTACK */
 
 /* It's common to want to use cpu_all_mask in struct member initializers,
-- 
2.12.2.715.g7642488e1d-goog

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