linux-kernel - [PATCH 2/3] x86/mce/AMD: Define a list_head for threshold blocks outside the list

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Date:   Wed, 24 May 2017 15:41:46 -0500
From:   Yazen Ghannam <Yazen.Ghannam@....com>
To:     <linux-edac@...r.kernel.org>
CC:     Borislav Petkov <bp@...e.de>, Tony Luck <tony.luck@...el.com>,
        <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: [PATCH 2/3] x86/mce/AMD: Define a list_head for threshold blocks outside the list

From: Yazen Ghannam <yazen.ghannam@....com>

There needs to be a list_head outside of a linked list in order to iterate
over it and have access to all its elements. This is because the
list_for_each* macros iterate starting from head->next rather than head.

Define a list_head for the threshold blocks list in struct threshold_bank
since this is the container of the list. Use this list_head as the head
instead of the first element in the blocks list.

This is needed in a future patch where we read the blocks list in the
threshold interrupt handler. Currently, we'll always skip block 0 since it
is the head of the list.

Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
---
 arch/x86/include/asm/amd_nb.h        |  2 ++
 arch/x86/kernel/cpu/mcheck/mce_amd.c | 19 ++++++++++---------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/amd_nb.h b/arch/x86/include/asm/amd_nb.h
index da181ad..81334b4 100644
--- a/arch/x86/include/asm/amd_nb.h
+++ b/arch/x86/include/asm/amd_nb.h
@@ -55,6 +55,8 @@ struct threshold_bank {
 	struct kobject		*kobj;
 	struct threshold_block	*blocks;
 
+	struct list_head	blocks_head;
+
 	/* initialized to the number of CPUs on the node sharing this bank */
 	refcount_t		cpus;
 };
diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index d11f94e..2074b870 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -1119,15 +1119,15 @@ static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank,
 		threshold_ktype.default_attrs[2] = NULL;
 	}
 
-	INIT_LIST_HEAD(&b->miscj);
-
-	if (per_cpu(threshold_banks, cpu)[bank]->blocks) {
-		list_add(&b->miscj,
-			 &per_cpu(threshold_banks, cpu)[bank]->blocks->miscj);
-	} else {
+	if (!per_cpu(threshold_banks, cpu)[bank]->blocks) {
+		INIT_LIST_HEAD(&per_cpu(threshold_banks, cpu)[bank]->blocks_head);
 		per_cpu(threshold_banks, cpu)[bank]->blocks = b;
 	}
 
+	INIT_LIST_HEAD(&b->miscj);
+
+	list_add(&b->miscj, &per_cpu(threshold_banks, cpu)[bank]->blocks_head);
+
 	err = kobject_init_and_add(&b->kobj, &threshold_ktype,
 				   per_cpu(threshold_banks, cpu)[bank]->kobj,
 				   get_name(bank, b));
@@ -1158,7 +1158,7 @@ static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank,
 
 static int __threshold_add_blocks(struct threshold_bank *b)
 {
-	struct list_head *head = &b->blocks->miscj;
+	struct list_head *head = &b->blocks_head;
 	struct threshold_block *pos = NULL;
 	struct threshold_block *tmp = NULL;
 	int err = 0;
@@ -1256,7 +1256,7 @@ static void deallocate_threshold_block(unsigned int cpu,
 	if (!head)
 		return;
 
-	list_for_each_entry_safe(pos, tmp, &head->blocks->miscj, miscj) {
+	list_for_each_entry_safe(pos, tmp, &head->blocks_head, miscj) {
 		kobject_put(&pos->kobj);
 		list_del(&pos->miscj);
 		kfree(pos);
@@ -1273,7 +1273,7 @@ static void __threshold_remove_blocks(struct threshold_bank *b)
 
 	kobject_del(b->kobj);
 
-	list_for_each_entry_safe(pos, tmp, &b->blocks->miscj, miscj)
+	list_for_each_entry_safe(pos, tmp, &b->blocks_head, miscj)
 		kobject_del(&pos->kobj);
 }
 
@@ -1307,6 +1307,7 @@ static void threshold_remove_bank(unsigned int cpu, int bank)
 	deallocate_threshold_block(cpu, bank);
 
 free_out:
+	list_del(&b->blocks_head);
 	kobject_del(b->kobj);
 	kobject_put(b->kobj);
 	kfree(b);
-- 
2.7.4