[PATCH 1/6] x86/mce: Don't print MCEs when mcelog is active

[Borislav Petkov]

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

Since

  cd9c57cad3fe ("x86/MCE: Dump MCE to dmesg if no consumers")

all MCEs are printed even when mcelog is running. Fix the regression to
not print to dmesg when mcelog is running as it is a consumer too.

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 4.10..
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx>
Cc: x86-ml <x86@xxxxxxxxxx>
Fixes: cd9c57cad3fe ("x86/MCE: Dump MCE to dmesg if no consumers")
Link: http://lkml.kernel.org/r/20170324003140.26400-1-andi@xxxxxxxxxxxxxx
[ Massage commit message. ]
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 5e365a2fabe5..e95e02734f25 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -55,6 +55,8 @@
 
 static DEFINE_MUTEX(mce_chrdev_read_mutex);
 
+static int mce_chrdev_open_count;	/* #times opened */
+
 #define mce_log_get_idx_check(p) \
 ({ \
 	RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
@@ -599,6 +601,10 @@ static int mce_default_notifier(struct notifier_block *nb, unsigned long val,
 	if (atomic_read(&num_notifiers) > 2)
 		return NOTIFY_DONE;
 
+	/* Don't print when mcelog is running */
+	if (mce_chrdev_open_count > 0)
+		return NOTIFY_DONE;
+
 	__print_mce(m);
 
 	return NOTIFY_DONE;
@@ -1848,7 +1854,6 @@ void mcheck_cpu_clear(struct cpuinfo_x86 *c)
  */
 
 static DEFINE_SPINLOCK(mce_chrdev_state_lock);
-static int mce_chrdev_open_count;	/* #times opened */
 static int mce_chrdev_open_exclu;	/* already open exclusive? */
 
 static int mce_chrdev_open(struct inode *inode, struct file *file)
-- 
2.11.0