linux-kernel - [PATCH] kernel/irq: Limit validation of cpumask_var_t to CONFIG_CPUMASK

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Message-Id: <20170411235217.71604-1-mka@chromium.org>
Date:   Tue, 11 Apr 2017 16:52:17 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Grant Grundler <grundler@...omium.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Michael Davidson <md@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH] kernel/irq: Limit validation of cpumask_var_t to CONFIG_CPUMASK_OFFSTACK=y

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

irq_thread_check_affinity() validates the cpumask_var_t field in the
interrupt descriptor by checking if it is not NULL. This works for
both CONFIG_CPUMASK_OFFSTACK=y/n, however clang raises the following
warning with 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]

To get rid of the warning only validate the cpumask_var_t field when
CONFIG_CPUMASK_OFFSTACK=y.

Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
 kernel/irq/manage.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index a4afe5cc5af1..5d38fe85122b 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -848,14 +848,14 @@ irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action)
 	}
 
 	raw_spin_lock_irq(&desc->lock);
-	/*
-	 * This code is triggered unconditionally. Check the affinity
-	 * mask pointer. For CPU_MASK_OFFSTACK=n this is optimized out.
-	 */
-	if (desc->irq_common_data.affinity)
-		cpumask_copy(mask, desc->irq_common_data.affinity);
-	else
+
+#ifdef CONFIG_CPUMASK_OFFSTACK
+	if (!desc->irq_common_data.affinity)
 		valid = false;
+	else
+#endif
+	cpumask_copy(mask, desc->irq_common_data.affinity);
+
 	raw_spin_unlock_irq(&desc->lock);
 
 	if (valid)
-- 
2.12.2.715.g7642488e1d-goog