linux-kernel - [PATCH 040/115] gpu: ion: Fix lockdep issue in ion_page

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Date:	Fri, 13 Dec 2013 14:24:14 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Jesse Barker <jesse.barker@....com>,
	Colin Cross <ccross@...roid.com>,
	Rebecca Schultz Zavin <rebecca@...roid.com>,
	John Stultz <john.stultz@...aro.org>
Subject: [PATCH 040/115] gpu: ion: Fix lockdep issue in ion_page_pool

From: Rebecca Schultz Zavin <rebecca@...roid.com>

Currently the mutex is held while kmalloc is called, under a low memory
condition this might trigger the shrinker which also takes this mutex.
Refactor so the mutex is not held during allocation.

Signed-off-by: Rebecca Schultz Zavin <rebecca@...roid.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/staging/android/ion/ion_page_pool.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/android/ion/ion_page_pool.c b/drivers/staging/android/ion/ion_page_pool.c
index ea45380..20790eb 100644
--- a/drivers/staging/android/ion/ion_page_pool.c
+++ b/drivers/staging/android/ion/ion_page_pool.c
@@ -53,6 +53,8 @@ static int ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
 	item = kmalloc(sizeof(struct ion_page_pool_item), GFP_KERNEL);
 	if (!item)
 		return -ENOMEM;
+
+	mutex_lock(&pool->mutex);
 	item->page = page;
 	if (PageHighMem(page)) {
 		list_add_tail(&item->list, &pool->high_items);
@@ -61,6 +63,7 @@ static int ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
 		list_add_tail(&item->list, &pool->low_items);
 		pool->low_count++;
 	}
+	mutex_unlock(&pool->mutex);
 	return 0;
 }
 
@@ -110,9 +113,7 @@ void ion_page_pool_free(struct ion_page_pool *pool, struct page* page)
 {
 	int ret;
 
-	mutex_lock(&pool->mutex);
 	ret = ion_page_pool_add(pool, page);
-	mutex_unlock(&pool->mutex);
 	if (ret)
 		ion_page_pool_free_pages(pool, page);
 }
-- 
1.8.3.2

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