linux-kernel - [PATCH] [2/3] x86: mce: Improve comments in CMCI code

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Message-Id: <20090711074410.958AB1D0261@basil.firstfloor.org>
Date:	Sat, 11 Jul 2009 09:44:10 +0200 (CEST)
From:	Andi Kleen <andi@...stfloor.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] [2/3] x86: mce: Improve comments in CMCI code


Improve the comments in the CMCI code in mce_intel.c. This documents
some of the design decisions and adds references to the appropiate
manuals. 

No code changes.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 arch/x86/kernel/cpu/mcheck/mce_intel.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

Index: linux/arch/x86/kernel/cpu/mcheck/mce_intel.c
===================================================================
--- linux.orig/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ linux/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -19,8 +19,16 @@
  * the CPU to raise an interrupt when a corrected machine check happened.
  * Normally we pick those up using a regular polling timer.
  * Also supports reliable discovery of shared banks.
+ *
+ * For reference see the Intel 64 Software Developer's Manual, Volume 3a,
+ * 15.5.2. This code is a relatively faithful implementation of the
+ * recommendations there.
  */
 
+/*
+ * Ownership of MCE banks per CPU. To avoid duplicated events
+ * for shared banks we assign ownership to specific CPUs.
+ */
 static DEFINE_PER_CPU(mce_banks_t, mce_banks_owned);
 
 /*
@@ -29,6 +37,10 @@ static DEFINE_PER_CPU(mce_banks_t, mce_b
  */
 static DEFINE_SPINLOCK(cmci_discover_lock);
 
+/*
+ * CMCI threshold in hardware has some drawbacks. We chose to log every event
+ * and hardcode 1
+ */
 #define CMCI_THRESHOLD 1
 
 static int cmci_supported(int *banks)
@@ -163,7 +175,7 @@ void cmci_clear(void)
 
 /*
  * After a CPU went down cycle through all the others and rediscover
- * Must run in process context.
+ * bank ownership.  Must run in process context.
  */
 void cmci_rediscover(int dying)
 {
--
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