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Subject[PATCH 04/60] driver core: Remove completion from struct klist_node
Date
From: Matthew Wilcox <matthew@wil.cx>

Removing the completion from klist_node reduces its size from 64 bytes
to 28 on x86-64. To maintain the semantics of klist_remove(), we add
a single list of klist nodes which are pending deletion and scan them.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
include/linux/klist.h | 2 --
lib/klist.c | 43 ++++++++++++++++++++++++++++++++++++++++---
2 files changed, 40 insertions(+), 5 deletions(-)
diff --git a/include/linux/klist.h b/include/linux/klist.h
index 8ea98db..d5a27af 100644
--- a/include/linux/klist.h
+++ b/include/linux/klist.h
@@ -13,7 +13,6 @@
#define _LINUX_KLIST_H

#include <linux/spinlock.h>
-#include <linux/completion.h>
#include <linux/kref.h>
#include <linux/list.h>

@@ -41,7 +40,6 @@ struct klist_node {
void *n_klist; /* never access directly */
struct list_head n_node;
struct kref n_ref;
- struct completion n_removed;
};

extern void klist_add_tail(struct klist_node *n, struct klist *k);
diff --git a/lib/klist.c b/lib/klist.c
index bbdd301..573d606 100644
--- a/lib/klist.c
+++ b/lib/klist.c
@@ -36,6 +36,7 @@

#include <linux/klist.h>
#include <linux/module.h>
+#include <linux/sched.h>

/*
* Use the lowest bit of n_klist to mark deleted nodes and exclude
@@ -108,7 +109,6 @@ static void add_tail(struct klist *k, struct klist_node *n)
static void klist_node_init(struct klist *k, struct klist_node *n)
{
INIT_LIST_HEAD(&n->n_node);
- init_completion(&n->n_removed);
kref_init(&n->n_ref);
knode_set_klist(n, k);
if (k->get)
@@ -171,13 +171,34 @@ void klist_add_before(struct klist_node *n, struct klist_node *pos)
}
EXPORT_SYMBOL_GPL(klist_add_before);

+struct klist_waiter {
+ struct list_head list;
+ struct klist_node *node;
+ struct task_struct *process;
+ int woken;
+};
+
+static DEFINE_SPINLOCK(klist_remove_lock);
+static LIST_HEAD(klist_remove_waiters);
+
static void klist_release(struct kref *kref)
{
+ struct klist_waiter *waiter, *tmp;
struct klist_node *n = container_of(kref, struct klist_node, n_ref);

WARN_ON(!knode_dead(n));
list_del(&n->n_node);
- complete(&n->n_removed);
+ spin_lock(&klist_remove_lock);
+ list_for_each_entry_safe(waiter, tmp, &klist_remove_waiters, list) {
+ if (waiter->node != n)
+ continue;
+
+ waiter->woken = 1;
+ mb();
+ wake_up_process(waiter->process);
+ list_del(&waiter->list);
+ }
+ spin_unlock(&klist_remove_lock);
knode_set_klist(n, NULL);
}

@@ -217,8 +238,24 @@ EXPORT_SYMBOL_GPL(klist_del);
*/
void klist_remove(struct klist_node *n)
{
+ struct klist_waiter waiter;
+
+ waiter.node = n;
+ waiter.process = current;
+ waiter.woken = 0;
+ spin_lock(&klist_remove_lock);
+ list_add(&waiter.list, &klist_remove_waiters);
+ spin_unlock(&klist_remove_lock);
+
klist_del(n);
- wait_for_completion(&n->n_removed);
+
+ for (;;) {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ if (waiter.woken)
+ break;
+ schedule();
+ }
+ __set_current_state(TASK_RUNNING);
}
EXPORT_SYMBOL_GPL(klist_remove);

--
1.6.0.4


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