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Message-ID: <4A36E6F2.5050708@opengridcomputing.com>
Date: Mon, 15 Jun 2009 19:27:30 -0500
From: Steve Wise <swise@...ngridcomputing.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: trivial@...nel.org, zygo.blaxell@...dros.com,
linux-kernel@...r.kernel.org, Jes Sorensen <jes@...ined-monkey.org>
Subject: Re: [PATCH] LIB: remove unmatched write_lock() in gen_pool_destroy
Andrew Morton wrote:
> On Mon, 15 Jun 2009 17:30:32 -0500
> Steve Wise <swise@...ngridcomputing.com> wrote:
>
>
>> Andrew Morton wrote:
>>
>>> On Mon, 15 Jun 2009 23:35:31 +0200 (CEST)
>>> Jiri Kosina <trivial@...nel.org> wrote:
>>>
>>>
>>>
>>>>> - write_lock(&pool->lock);
>>>>> list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
>>>>> chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
>>>>> list_del(&chunk->next_chunk);
>>>>> --
>>>>> 1.5.6.5
>>>>>
>>>>>
>>>>>
>>>> Hi Zygo,
>>>>
>>>> this doesn't really qualify for trivial tree, as it introduces a
>>>> significant code change. Adding some CCs.
>>>>
>>>>
>>> yep, I merged it, thanks.
>>>
>>> I wonder why drivers/infiniband/hw/cxgb3 users never noticed this.
>>>
>>>
>> I seem to remember trying to get this removed a few years ago and the
>> owner didn't want it removed...
>>
>>
>
> void gen_pool_destroy(struct gen_pool *pool)
> {
> struct list_head *_chunk, *_next_chunk;
> struct gen_pool_chunk *chunk;
> int order = pool->min_alloc_order;
> int bit, end_bit;
>
>
> write_lock(&pool->lock);
> list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
> chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
> list_del(&chunk->next_chunk);
>
> end_bit = (chunk->end_addr - chunk->start_addr) >> order;
> bit = find_next_bit(chunk->bits, end_bit, 0);
> BUG_ON(bit < end_bit);
>
> kfree(chunk);
> }
> kfree(pool);
> return;
> }
>
> The write_lock is unneeded and wrong. Because if any other thread of
> control is concurrently playing with this pool, it will sometimes do a
> use-after-free.
>
> So no other thread of control should have access to this pool, so
> there's no need for the write_lock().
>
Yup.
My original patch adding gen_pool_destroy() didn't have the
write_lock(). It was added as part of "reviewing" the patch. :)
Steve.
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