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

[Yazen Ghannam]

From: Yazen Ghannam <yazen.ghan...@amd.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.ghan...@amd.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