[03/04 mm-patch, rfc] Add lightweight rwlock to net/dccp/ccid.c (was Re: [mm-patch] bluetooth: use GFP_ATOMIC in *_sock_create's sk_alloc)

Frederik Deweerdt
2006-07-28T16:28:24Z

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This patch is part of the lw_rwlock patchset, it removes the
ccids_{read,write}_{lock,unlock} functions which have been moved
to linux/lw_rwlock.h and made more generic.

Signed-off-by: Frederik Deweerdt <frederik.deweerdt@gmail.com>

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--- v2.6.18-rc2-mm1~ori/net/dccp/ccid.c 2006-06-18 03:49:35.000000000 +0200
+++ v2.6.18-rc2-mm1/net/dccp/ccid.c 2006-07-28 16:19:32.000000000 +0200
@@ -12,48 +12,11 @@
*/

#include "ccid.h"
+#include <linux/lw_rwlock.h>

static struct ccid_operations *ccids[CCID_MAX];
-#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
-static atomic_t ccids_lockct = ATOMIC_INIT(0);
-static DEFINE_SPINLOCK(ccids_lock);
-
-/*
- * The strategy is: modifications ccids vector are short, do not sleep and
- * veeery rare, but read access should be free of any exclusive locks.
- */
-static void ccids_write_lock(void)
-{
- spin_lock(&ccids_lock);
- while (atomic_read(&ccids_lockct) != 0) {
- spin_unlock(&ccids_lock);
- yield();
- spin_lock(&ccids_lock);
- }
-}
-
-static inline void ccids_write_unlock(void)
-{
- spin_unlock(&ccids_lock);
-}
+static DEFINE_LW_RWLOCK(ccids_lock);

-static inline void ccids_read_lock(void)
-{
- atomic_inc(&ccids_lockct);
- spin_unlock_wait(&ccids_lock);
-}
-
-static inline void ccids_read_unlock(void)
-{
- atomic_dec(&ccids_lockct);
-}
-
-#else
-#define ccids_write_lock() do { } while(0)
-#define ccids_write_unlock() do { } while(0)
-#define ccids_read_lock() do { } while(0)
-#define ccids_read_unlock() do { } while(0)
-#endif

static kmem_cache_t *ccid_kmem_cache_create(int obj_size, const char *fmt,...)
{
@@ -103,13 +66,13 @@ int ccid_register(struct ccid_operations
if (ccid_ops->ccid_hc_tx_slab == NULL)
goto out_free_rx_slab;

- ccids_write_lock();
+ lw_write_lock(&ccids_lock);
err = -EEXIST;
if (ccids[ccid_ops->ccid_id] == NULL) {
ccids[ccid_ops->ccid_id] = ccid_ops;
err = 0;
}
- ccids_write_unlock();
+ lw_write_unlock(&ccids_lock);
if (err != 0)
goto out_free_tx_slab;

@@ -131,9 +94,9 @@ EXPORT_SYMBOL_GPL(ccid_register);

int ccid_unregister(struct ccid_operations *ccid_ops)
{
- ccids_write_lock();
+ lw_write_lock(&ccids_lock);
ccids[ccid_ops->ccid_id] = NULL;
- ccids_write_unlock();
+ lw_write_unlock(&ccids_lock);

ccid_kmem_cache_destroy(ccid_ops->ccid_hc_tx_slab);
ccid_ops->ccid_hc_tx_slab = NULL;
@@ -152,15 +115,15 @@ struct ccid *ccid_new(unsigned char id,
struct ccid_operations *ccid_ops;
struct ccid *ccid = NULL;

- ccids_read_lock();
+ lw_read_lock(&ccids_lock);
#ifdef CONFIG_KMOD
if (ccids[id] == NULL) {
/* We only try to load if in process context */
- ccids_read_unlock();
+ lw_read_unlock(&ccids_lock);
if (gfp & GFP_ATOMIC)
goto out;
request_module("net-dccp-ccid-%d", id);
- ccids_read_lock();
+ lw_read_lock(&ccids_lock);
}
#endif
ccid_ops = ccids[id];
@@ -170,7 +133,7 @@ struct ccid *ccid_new(unsigned char id,
if (!try_module_get(ccid_ops->ccid_owner))
goto out_unlock;

- ccids_read_unlock();
+ lw_read_unlock(&ccids_lock);

ccid = kmem_cache_alloc(rx ? ccid_ops->ccid_hc_rx_slab :
ccid_ops->ccid_hc_tx_slab, gfp);
@@ -191,7 +154,7 @@ struct ccid *ccid_new(unsigned char id,
out:
return ccid;
out_unlock:
- ccids_read_unlock();
+ lw_read_unlock(&ccids_lock);
goto out;
out_free_ccid:
kmem_cache_free(rx ? ccid_ops->ccid_hc_rx_slab :
@@ -235,10 +198,10 @@ static void ccid_delete(struct ccid *cci
ccid_ops->ccid_hc_tx_exit(sk);
kmem_cache_free(ccid_ops->ccid_hc_tx_slab, ccid);
}
- ccids_read_lock();
+ lw_read_lock(&ccids_lock);
if (ccids[ccid_ops->ccid_id] != NULL)
module_put(ccid_ops->ccid_owner);
- ccids_read_unlock();
+ lw_read_unlock(&ccids_lock);
}

void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk)