linux-kernel - [PATCH] kernel/profile: Use cpumask_available to check for NULL cpumask

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Message-Id: <20191022191957.9554-1-natechancellor@gmail.com>
Date:   Tue, 22 Oct 2019 12:19:57 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] kernel/profile: Use cpumask_available to check for NULL cpumask

When building with clang + -Wtautological-pointer-compare, these
instances pop up:

kernel/profile.c:339:6: warning: comparison of array 'prof_cpu_mask' not
equal to a null pointer is always true [-Wtautological-pointer-compare]
        if (prof_cpu_mask != NULL)
            ^~~~~~~~~~~~~    ~~~~
kernel/profile.c:376:6: warning: comparison of array 'prof_cpu_mask' not
equal to a null pointer is always true [-Wtautological-pointer-compare]
        if (prof_cpu_mask != NULL)
            ^~~~~~~~~~~~~    ~~~~
kernel/profile.c:406:26: warning: comparison of array 'prof_cpu_mask'
not equal to a null pointer is always true
[-Wtautological-pointer-compare]
        if (!user_mode(regs) && prof_cpu_mask != NULL &&
                                ^~~~~~~~~~~~~    ~~~~
3 warnings generated.

This can be addressed with the cpumask_available helper, introduced in
commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") to fix
warnings like this while keeping the code the same.

Link: https://github.com/ClangBuiltLinux/linux/issues/747
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 kernel/profile.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/profile.c b/kernel/profile.c
index af7c94bf5fa1..4b144b02ca5d 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -336,7 +336,7 @@ static int profile_dead_cpu(unsigned int cpu)
 	struct page *page;
 	int i;
 
-	if (prof_cpu_mask != NULL)
+	if (cpumask_available(prof_cpu_mask))
 		cpumask_clear_cpu(cpu, prof_cpu_mask);
 
 	for (i = 0; i < 2; i++) {
@@ -373,7 +373,7 @@ static int profile_prepare_cpu(unsigned int cpu)
 
 static int profile_online_cpu(unsigned int cpu)
 {
-	if (prof_cpu_mask != NULL)
+	if (cpumask_available(prof_cpu_mask))
 		cpumask_set_cpu(cpu, prof_cpu_mask);
 
 	return 0;
@@ -403,7 +403,7 @@ void profile_tick(int type)
 {
 	struct pt_regs *regs = get_irq_regs();
 
-	if (!user_mode(regs) && prof_cpu_mask != NULL &&
+	if (!user_mode(regs) && cpumask_available(prof_cpu_mask) &&
 	    cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 		profile_hit(type, (void *)profile_pc(regs));
 }
-- 
2.23.0