Re: [PATCH] powerpc/pseries: avoid harmless preempt warning

[Christophe Leroy]

Le 20/03/2020 à 16:24, Nicholas Piggin a écrit :

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
  arch/powerpc/platforms/pseries/lpar.c | 10 +++++++++-
  1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/lpar.c 
b/arch/powerpc/platforms/pseries/lpar.c
index 3c3da25b445c..e4ed5317f117 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -636,8 +636,16 @@ static const struct proc_ops 
vcpudispatch_stats_freq_proc_ops = {

static int __init vcpudispatch_stats_procfs_init(void)

  {
-       if (!lppaca_shared_proc(get_lppaca()))
+       /*
+        * Avoid smp_processor_id while preemptible. All CPUs should have
+        * the same value for lppaca_shared_proc.
+        */
+       preempt_disable();
+       if (!lppaca_shared_proc(get_lppaca())) {
+               preempt_enable();
                return 0;
+       }
+       preempt_enable();

Can we avoid the double preempt_enable() with something like:

        preempt_disable();
        is_shared = lppaca_shared_proc(get_lppaca());
        preempt_enable();
        if (!is_shared)
                return 0;

if (!proc_create("powerpc/vcpudispatch_stats", 0600, NULL,

                                        &vcpudispatch_stats_proc_ops))

Christophe