From: Ohad Ben-Cohen <o...@wizery.com>

rwlocks are slower and have potential starvation issues
therefore spinlocks are generally preferred.

see also: http://lwn.net/Articles/364583/

Signed-off-by: Ohad Ben-Cohen <o...@wizery.com>
Signed-off-by: Kanigeri Hari <h-kanige...@ti.com>
Signed-off-by: Hiroshi DOYU <hiroshi.d...@nokia.com>
---
 arch/arm/plat-omap/mailbox.c |   30 +++++++++++++++---------------
 1 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/arm/plat-omap/mailbox.c b/arch/arm/plat-omap/mailbox.c
index 08a2df7..af3a6ac 100644
--- a/arch/arm/plat-omap/mailbox.c
+++ b/arch/arm/plat-omap/mailbox.c
@@ -31,7 +31,7 @@
 
 static struct workqueue_struct *mboxd;
 static struct omap_mbox *mboxes;
-static DEFINE_RWLOCK(mboxes_lock);
+static DEFINE_SPINLOCK(mboxes_lock);
 
 static int mbox_configured;
 
@@ -249,16 +249,16 @@ static int omap_mbox_startup(struct omap_mbox *mbox)
        struct omap_mbox_queue *mq;
 
        if (likely(mbox->ops->startup)) {
-               write_lock(&mboxes_lock);
+               spin_lock(&mboxes_lock);
                if (!mbox_configured)
                        ret = mbox->ops->startup(mbox);
 
                if (unlikely(ret)) {
-                       write_unlock(&mboxes_lock);
+                       spin_unlock(&mboxes_lock);
                        return ret;
                }
                mbox_configured++;
-               write_unlock(&mboxes_lock);
+               spin_unlock(&mboxes_lock);
        }
 
        ret = request_irq(mbox->irq, mbox_interrupt, IRQF_SHARED,
@@ -304,12 +304,12 @@ static void omap_mbox_fini(struct omap_mbox *mbox)
        free_irq(mbox->irq, mbox);
 
        if (unlikely(mbox->ops->shutdown)) {
-               write_lock(&mboxes_lock);
+               spin_lock(&mboxes_lock);
                if (mbox_configured > 0)
                        mbox_configured--;
                if (!mbox_configured)
                        mbox->ops->shutdown(mbox);
-               write_unlock(&mboxes_lock);
+               spin_unlock(&mboxes_lock);
        }
 }
 
@@ -330,14 +330,14 @@ struct omap_mbox *omap_mbox_get(const char *name)
        struct omap_mbox *mbox;
        int ret;
 
-       read_lock(&mboxes_lock);
+       spin_lock(&mboxes_lock);
        mbox = *(find_mboxes(name));
        if (mbox == NULL) {
-               read_unlock(&mboxes_lock);
+               spin_unlock(&mboxes_lock);
                return ERR_PTR(-ENOENT);
        }
 
-       read_unlock(&mboxes_lock);
+       spin_unlock(&mboxes_lock);
 
        ret = omap_mbox_startup(mbox);
        if (ret)
@@ -363,15 +363,15 @@ int omap_mbox_register(struct device *parent, struct 
omap_mbox *mbox)
        if (mbox->next)
                return -EBUSY;
 
-       write_lock(&mboxes_lock);
+       spin_lock(&mboxes_lock);
        tmp = find_mboxes(mbox->name);
        if (*tmp) {
                ret = -EBUSY;
-               write_unlock(&mboxes_lock);
+               spin_unlock(&mboxes_lock);
                goto err_find;
        }
        *tmp = mbox;
-       write_unlock(&mboxes_lock);
+       spin_unlock(&mboxes_lock);
 
        return 0;
 
@@ -384,18 +384,18 @@ int omap_mbox_unregister(struct omap_mbox *mbox)
 {
        struct omap_mbox **tmp;
 
-       write_lock(&mboxes_lock);
+       spin_lock(&mboxes_lock);
        tmp = &mboxes;
        while (*tmp) {
                if (mbox == *tmp) {
                        *tmp = mbox->next;
                        mbox->next = NULL;
-                       write_unlock(&mboxes_lock);
+                       spin_unlock(&mboxes_lock);
                        return 0;
                }
                tmp = &(*tmp)->next;
        }
-       write_unlock(&mboxes_lock);
+       spin_unlock(&mboxes_lock);
 
        return -EINVAL;
 }
-- 
1.7.1.rc1

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