The patch titled
mm/dmapool.c: take lock only once in dma_pool_free()
has been added to the -mm tree. Its filename is
mm-dmapoolc-take-lock-only-once-in-dma_pool_free.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: mm/dmapool.c: take lock only once in dma_pool_free()
From: Rolf Eike Beer <eike-kernel@xxxxxxxxx>
dma_pool_free() scans for the page to free in the pool list holding the
pool lock. Then it releases the lock basically to acquire it immediately
again. Modify the code to only take the lock once.
This will do some additional loops and computations with the lock held in
if memory debugging is activated. If it is not activated the only new
operations with this lock is one if and one substraction.
Signed-off-by: Rolf Eike Beer <eike-kernel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/dmapool.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff -puN mm/dmapool.c~mm-dmapoolc-take-lock-only-once-in-dma_pool_free mm/dmapool.c
--- a/mm/dmapool.c~mm-dmapoolc-take-lock-only-once-in-dma_pool_free
+++ a/mm/dmapool.c
@@ -355,20 +355,15 @@ EXPORT_SYMBOL(dma_pool_alloc);
static struct dma_page *pool_find_page(struct dma_pool *pool, dma_addr_t dma)
{
- unsigned long flags;
struct dma_page *page;
- spin_lock_irqsave(&pool->lock, flags);
list_for_each_entry(page, &pool->page_list, page_list) {
if (dma < page->dma)
continue;
if (dma < (page->dma + pool->allocation))
- goto done;
+ return page;
}
- page = NULL;
- done:
- spin_unlock_irqrestore(&pool->lock, flags);
- return page;
+ return NULL;
}
/**
@@ -386,8 +381,10 @@ void dma_pool_free(struct dma_pool *pool
unsigned long flags;
unsigned int offset;
+ spin_lock_irqsave(&pool->lock, flags);
page = pool_find_page(pool, dma);
if (!page) {
+ spin_unlock_irqrestore(&pool->lock, flags);
if (pool->dev)
dev_err(pool->dev,
"dma_pool_free %s, %p/%lx (bad dma)\n",
@@ -401,6 +398,7 @@ void dma_pool_free(struct dma_pool *pool
offset = vaddr - page->vaddr;
#ifdef DMAPOOL_DEBUG
if ((dma - page->dma) != offset) {
+ spin_unlock_irqrestore(&pool->lock, flags);
if (pool->dev)
dev_err(pool->dev,
"dma_pool_free %s, %p (bad vaddr)/%Lx\n",
@@ -418,6 +416,7 @@ void dma_pool_free(struct dma_pool *pool
chain = *(int *)(page->vaddr + chain);
continue;
}
+ spin_unlock_irqrestore(&pool->lock, flags);
if (pool->dev)
dev_err(pool->dev, "dma_pool_free %s, dma %Lx "
"already free\n", pool->name,
@@ -432,7 +431,6 @@ void dma_pool_free(struct dma_pool *pool
memset(vaddr, POOL_POISON_FREED, pool->size);
#endif
- spin_lock_irqsave(&pool->lock, flags);
page->in_use--;
*(int *)vaddr = page->offset;
page->offset = offset;
_
Patches currently in -mm which might be from eike-kernel@xxxxxxxxx are
linux-next.patch
mm-dmapoolc-take-lock-only-once-in-dma_pool_free.patch
mm-dmapoolc-use-task_uninterruptible-in-dma_pool_alloc.patch
include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit.patch
include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit-fix.patch
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