From: majianpeng <majianpeng@gmail.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-mm <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Re: [PATCH 2/3] mm/kmemleak.c: Use list_for_each_entry_safe to reconstruct function scan_gray_list
Date: Mon, 3 Jun 2013 08:58:49 +0800 [thread overview]
Message-ID: <201306030858459339090@gmail.com> (raw)
In-Reply-To: 20130530144028.GF23631@arm.com
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="gb2312", Size: 1995 bytes --]
>On Tue, May 14, 2013 at 12:49:44PM +0100, majianpeng wrote:
>> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
>> ---
>> mm/kmemleak.c | 8 +-------
>> 1 file changed, 1 insertion(+), 7 deletions(-)
>>
>> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
>> index b1525db..f0ece93 100644
>> --- a/mm/kmemleak.c
>> +++ b/mm/kmemleak.c
>> @@ -1225,22 +1225,16 @@ static void scan_gray_list(void)
>> * from inside the loop. The kmemleak objects cannot be freed from
>> * outside the loop because their use_count was incremented.
>> */
>> - object = list_entry(gray_list.next, typeof(*object), gray_list);
>> - while (&object->gray_list != &gray_list) {
>> + list_for_each_entry_safe(object, tmp, &gray_list, gray_list) {
>> cond_resched();
>>
>> /* may add new objects to the list */
>> if (!scan_should_stop())
>> scan_object(object);
>>
>> - tmp = list_entry(object->gray_list.next, typeof(*object),
>> - gray_list);
>> -
>> /* remove the object from the list and release it */
>> list_del(&object->gray_list);
>> put_object(object);
>> -
>> - object = tmp;
>> }
>> WARN_ON(!list_empty(&gray_list));
>
>I tried this patch for a few days and I hit the WARN_ON after the loop.
>During scanning, new entries may be added at the end of the loop but we
>need to loop until all the entries have been removed. I probably had a
>reason why I had the 'while' loop.
>
>The key difference is that list_for_each_entry_safe() gets the next
>entry (n or tmp above) before scan_object() and it may hit the end of
>the list. However, scan_object() may do a list_add_tail(&gray_list)
>hence we need to get the next entry after this function.
>
>Basically list_for_each_entry_safe() is not safe with tail additions.
>I'll revert this patch (hasn't reached mainline anyway).
>
Ok, i see.
Thanks!
>Thanks.
>
>--
>CatalinN§²æìr¸zǧu©²Æ {\béì¹»\x1c®&Þ)îÆi¢Ø^nr¶Ý¢j$½§$¢¸\x05¢¹¨è§~'.)îÄÃ,yèm¶ÿÃ\f%{±j+ðèצj)Z·
prev parent reply other threads:[~2013-06-03 0:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-14 11:49 [PATCH 2/3] mm/kmemleak.c: Use list_for_each_entry_safe to reconstruct function scan_gray_list majianpeng
2013-05-30 14:40 ` Catalin Marinas
2013-06-03 0:58 ` majianpeng [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201306030858459339090@gmail.com \
--to=majianpeng@gmail.com \
--cc=catalin.marinas@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).