kernel/profile.c: 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 c738f03d101f ("cpumask: Add helper cpumask_available()") to fix
warnings like this while keeping the code the same.

Link: https://github.com/ClangBuiltLinux/linux/issues/747
Link: http://lkml.kernel.org/r/20191022191957.9554-1-natechancellor@gmail.com
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/profile.c b/kernel/profile.c
index af7c94bf5fa1dbc7305fcbd57c6f6aea3a0fd33b..4b144b02ca5d91c7b60a96384b223c04c6311acf 100644 (file)
--- 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));
 }