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Message-ID: <20081002214308.GP13822@parisc-linux.org>
Date: Thu, 2 Oct 2008 15:43:08 -0600
From: Matthew Wilcox <matthew@....cx>
To: Greg KH <greg@...ah.com>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] Remove completion from struct klist_node
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@...ux.intel.com>
include/linux/klist.h | 2 --
lib/klist.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 44 insertions(+), 6 deletions(-)
diff --git a/include/linux/klist.h b/include/linux/klist.h
index 06c338e..989a335 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 {
struct klist *n_klist;
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 cca37f9..2b609ee 100644
--- a/lib/klist.c
+++ b/lib/klist.c
@@ -36,7 +36,7 @@
#include <linux/klist.h>
#include <linux/module.h>
-
+#include <linux/sched.h>
/**
* klist_init - Initialize a klist structure.
@@ -77,7 +77,6 @@ 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);
n->n_klist = k;
if (k->get)
@@ -140,12 +139,36 @@ void klist_add_before(struct klist_node *n, struct klist_node *pos)
}
EXPORT_SYMBOL_GPL(klist_add_before);
+struct klist_waiter {
+ struct klist_waiter *next;
+ struct klist_node *node;
+ struct task_struct *process;
+ int woken;
+};
+
+static DEFINE_SPINLOCK(klist_remove_lock);
+static struct klist_waiter *klist_remove_waiters;
+
static void klist_release(struct kref *kref)
{
+ struct klist_waiter **pprev, *this;
struct klist_node *n = container_of(kref, struct klist_node, n_ref);
list_del(&n->n_node);
- complete(&n->n_removed);
+ spin_lock(&klist_remove_lock);
+ pprev = &klist_remove_waiters;
+ while ((this = *pprev)) {
+ if (this->node != n) {
+ pprev = &this->next;
+ continue;
+ }
+
+ this->woken = 1;
+ mb();
+ wake_up_process(this->process);
+ *pprev = this->next;
+ }
+ spin_unlock(&klist_remove_lock);
n->n_klist = NULL;
}
@@ -178,8 +201,25 @@ 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);
+ waiter.next = klist_remove_waiters;
+ klist_remove_waiters = &waiter;
+ 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);
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
--
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