linux-kernel - [PATCH 4.19 21/28] x86/mmiotrace: Use cpumask_available() for cpumask_var

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Message-Id: <20200605140253.634271247@linuxfoundation.org>
Date:   Fri,  5 Jun 2020 16:15:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sedat Dilek <sedat.dilek@...il.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Borislav Petkov <bp@...e.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 21/28] x86/mmiotrace: Use cpumask_available() for cpumask_var_t variables

From: Nathan Chancellor <natechancellor@...il.com>

[ Upstream commit d7110a26e5905ec2fe3fc88bc6a538901accb72b ]

When building with Clang + -Wtautological-compare and
CONFIG_CPUMASK_OFFSTACK unset:

  arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
  equal to a null pointer is always false [-Wtautological-pointer-compare]
          if (downed_cpus == NULL &&
              ^~~~~~~~~~~    ~~~~
  arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
  equal to a null pointer is always false [-Wtautological-pointer-compare]
          if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
              ^~~~~~~~~~~    ~~~~
  2 warnings generated.

Commit

  f7e30f01a9e2 ("cpumask: Add helper cpumask_available()")

added cpumask_available() to fix warnings of this nature. Use that here
so that clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's
value.

Reported-by: Sedat Dilek <sedat.dilek@...il.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/982
Link: https://lkml.kernel.org/r/20200408205323.44490-1-natechancellor@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/mm/mmio-mod.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
index 2c1ecf4763c4..e32b003e064a 100644
--- a/arch/x86/mm/mmio-mod.c
+++ b/arch/x86/mm/mmio-mod.c
@@ -384,7 +384,7 @@ static void enter_uniprocessor(void)
 	int cpu;
 	int err;
 
-	if (downed_cpus == NULL &&
+	if (!cpumask_available(downed_cpus) &&
 	    !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
 		pr_notice("Failed to allocate mask\n");
 		goto out;
@@ -414,7 +414,7 @@ static void leave_uniprocessor(void)
 	int cpu;
 	int err;
 
-	if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
+	if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
 		return;
 	pr_notice("Re-enabling CPUs...\n");
 	for_each_cpu(cpu, downed_cpus) {
-- 
2.25.1