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    Subject[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)
    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>

    --- 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)
    \
     
     \ /
      Last update: 2006-07-28 18:31    [W:0.027 / U:0.972 seconds]
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