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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Matthias Kaehlcke <mka@chromium.org>,
        Grant Grundler <grundler@chromium.org>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Greg Hackmann <ghackmann@google.com>,
        Michael Davidson <md@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH 4.9 018/102] cpumask: Add helper cpumask_available()
Date:   Fri,  6 Apr 2018 15:22:59 +0200
Message-Id: <20180406084334.167293827@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Kaehlcke <mka@chromium.org>

commit f7e30f01a9e221067bb4b579e3cfc25cd2617467 upstream.

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>
Cc: Grant Grundler <grundler@chromium.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Michael Davidson <md@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20170412182030.83657-1-mka@chromium.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -680,6 +680,11 @@ void alloc_bootmem_cpumask_var(cpumask_v
 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];
 
@@ -720,6 +725,11 @@ static inline void free_cpumask_var(cpum
 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,