linux-kernel - [PATCH 5/5] x86/mce: Change default mce logger to check mce->handled

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Message-Id: <20200212204652.1489-6-tony.luck@intel.com>
Date:   Wed, 12 Feb 2020 12:46:52 -0800
From:   Tony Luck <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Tony Luck <tony.luck@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 5/5] x86/mce: Change default mce logger to check mce->handled

Instead of keeping count of how many handlers are registered on the
mce chain and printing if we are below some magic value. Look at the
mce->handled to see if anyone claims to have handled/logged this error.

[debug to always print in this version]

Signed-off-by: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/mce/core.c | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index ce7a78872f8f..5b73df383300 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -156,29 +156,17 @@ void mce_log(struct mce *m)
 }
 EXPORT_SYMBOL_GPL(mce_log);
 
-/*
- * We run the default notifier if we have only the UC, the first and the
- * default notifier registered. I.e., the mandatory NUM_DEFAULT_NOTIFIERS
- * notifiers registered on the chain.
- */
-#define NUM_DEFAULT_NOTIFIERS	3
-static atomic_t num_notifiers;
-
 void mce_register_decode_chain(struct notifier_block *nb)
 {
 	if (WARN_ON(nb->priority > MCE_PRIO_MCELOG && nb->priority < MCE_PRIO_EDAC))
 		return;
 
-	atomic_inc(&num_notifiers);
-
 	blocking_notifier_chain_register(&x86_mce_decoder_chain, nb);
 }
 EXPORT_SYMBOL_GPL(mce_register_decode_chain);
 
 void mce_unregister_decode_chain(struct notifier_block *nb)
 {
-	atomic_dec(&num_notifiers);
-
 	blocking_notifier_chain_unregister(&x86_mce_decoder_chain, nb);
 }
 EXPORT_SYMBOL_GPL(mce_unregister_decode_chain);
@@ -261,6 +249,8 @@ static void __print_mce(struct mce *m)
 	}
 
 	pr_cont("\n");
+	if (m->handled)
+		pr_emerg(HW_ERR "handled = %x\n", m->handled);
 	/*
 	 * Note this output is parsed by external tools and old fields
 	 * should not be changed.
@@ -600,10 +590,8 @@ static int mce_default_notifier(struct notifier_block *nb, unsigned long val,
 	if (!m)
 		return NOTIFY_DONE;
 
-	if (atomic_read(&num_notifiers) > NUM_DEFAULT_NOTIFIERS)
-		return NOTIFY_DONE;
-
-	__print_mce(m);
+	if (1 || !m->handled)
+		__print_mce(m);
 
 	return NOTIFY_DONE;
 }
-- 
2.21.1