From: Andrew Morton <akpm@linux-foundation.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: kbuild@lists.01.org, Mel Gorman <mgorman@suse.de>,
lkp@intel.com, kbuild-all@lists.01.org,
Linux Memory Management List <linux-mm@kvack.org>,
Nicolas Saenz Julienne <nsaenzju@redhat.com>
Subject: Re: [kbuild] [linux-next:master 7884/8197] mm/page_alloc.c:3813 rmqueue_pcplist() warn: inconsistent returns 'flags'.
Date: Thu, 7 Jul 2022 13:08:46 -0700 [thread overview]
Message-ID: <20220707130846.e3eb6b2f9f624a357c2c2ca5@linux-foundation.org> (raw)
In-Reply-To: <202207071103.r5a2F97A-lkp@intel.com>
On Thu, 7 Jul 2022 09:44:03 +0300 Dan Carpenter <dan.carpenter@oracle.com> wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head: 088b9c375534d905a4d337c78db3b3bfbb52c4a0
> commit: fdd1b94629bb5592abf40d0c7a572b58e4c0cadc [7884/8197] mm/page_alloc: protect PCP lists with a spinlock
> config: i386-randconfig-m021
> compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> smatch warnings:
> mm/page_alloc.c:3813 rmqueue_pcplist() warn: inconsistent returns 'flags'.
>
> vim +/flags +3813 mm/page_alloc.c
>
> 066b23935578d39 Mel Gorman 2017-02-24 3774 static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> 44042b4498728f4 Mel Gorman 2021-06-28 3775 struct zone *zone, unsigned int order,
> 44042b4498728f4 Mel Gorman 2021-06-28 3776 gfp_t gfp_flags, int migratetype,
> 44042b4498728f4 Mel Gorman 2021-06-28 3777 unsigned int alloc_flags)
> 066b23935578d39 Mel Gorman 2017-02-24 3778 {
> 066b23935578d39 Mel Gorman 2017-02-24 3779 struct per_cpu_pages *pcp;
> 066b23935578d39 Mel Gorman 2017-02-24 3780 struct list_head *list;
> 066b23935578d39 Mel Gorman 2017-02-24 3781 struct page *page;
> d34b0733b452ca3 Mel Gorman 2017-04-20 3782 unsigned long flags;
> fdd1b94629bb559 Mel Gorman 2022-06-24 3783 unsigned long __maybe_unused UP_flags;
> 066b23935578d39 Mel Gorman 2017-02-24 3784
> dbbee9d5cd83f9d Mel Gorman 2021-06-28 3785 local_lock_irqsave(&pagesets.lock, flags);
> 3b12e7e97938424 Mel Gorman 2021-06-28 3786
> fdd1b94629bb559 Mel Gorman 2022-06-24 3787 /*
> fdd1b94629bb559 Mel Gorman 2022-06-24 3788 * spin_trylock may fail due to a parallel drain. In the future, the
> fdd1b94629bb559 Mel Gorman 2022-06-24 3789 * trylock will also protect against IRQ reentrancy.
> fdd1b94629bb559 Mel Gorman 2022-06-24 3790 */
> fdd1b94629bb559 Mel Gorman 2022-06-24 3791 pcp = this_cpu_ptr(zone->per_cpu_pageset);
> fdd1b94629bb559 Mel Gorman 2022-06-24 3792 pcp_trylock_prepare(UP_flags);
> fdd1b94629bb559 Mel Gorman 2022-06-24 3793 if (!spin_trylock(&pcp->lock)) {
> fdd1b94629bb559 Mel Gorman 2022-06-24 3794 pcp_trylock_finish(UP_flags);
>
> Need to local_unlock_irqrestore(&pagesets.lock, flags); before return
oops. Looks right.
--- a/mm/page_alloc.c~mm-page_alloc-protect-pcp-lists-with-a-spinlock-fix
+++ a/mm/page_alloc.c
@@ -3792,6 +3792,7 @@ static struct page *rmqueue_pcplist(stru
pcp_trylock_prepare(UP_flags);
if (!spin_trylock(&pcp->lock)) {
pcp_trylock_finish(UP_flags);
+ local_unlock_irqrestore(&pagesets.lock, flags);
return NULL;
}
Do we really need the pcp_trylock_prepare/finish in there?
local_lock_irqsave() already did that.
next prev parent reply other threads:[~2022-07-07 20:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-07 6:44 Dan Carpenter
2022-07-07 20:08 ` Andrew Morton [this message]
2022-07-08 10:48 ` Mel Gorman
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