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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html