linux-kernel - Re: [mm/page_alloc] 2bd8eec68f: BUG:sleeping_function_called_from_invalid_context_at

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Message-ID: <20220706095535.GD27531@techsingularity.net>
Date:   Wed, 6 Jul 2022 10:55:35 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Oliver Sang <oliver.sang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        0day robot <lkp@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        lkp@...ts.01.org, Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [mm/page_alloc]  2bd8eec68f:
 BUG:sleeping_function_called_from_invalid_context_at_mm/gup.c

On Tue, Jul 05, 2022 at 09:51:25PM +0800, Oliver Sang wrote:
> Hi Andrew Morton,
> 
> On Sun, Jul 03, 2022 at 01:22:09PM -0700, Andrew Morton wrote:
> > On Sun, 3 Jul 2022 17:44:30 +0800 kernel test robot <oliver.sang@...el.com> wrote:
> > 
> > > FYI, we noticed the following commit (built with gcc-11):
> > > 
> > > commit: 2bd8eec68f740608db5ea58ecff06965228764cb ("[PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock")
> > > url: https://github.com/intel-lab-lkp/linux/commits/Mel-Gorman/Drain-remote-per-cpu-directly/20220613-230139
> > > base: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git b13baccc3850ca8b8cccbf8ed9912dbaa0fdf7f3
> > > patch link: https://lore.kernel.org/lkml/20220613125622.18628-8-mgorman@techsingularity.net
> > > 
> > 
> > Did this test include the followup patch
> > mm-page_alloc-replace-local_lock-with-normal-spinlock-fix.patch?
> 
> no, we just fetched original patch set and test upon it.
> 
> now we applied the patch you pointed to us upon 2bd8eec68f and found the issue
> still exist.
> (attached dmesg FYI)
> 

Thanks Oliver.

The trace is odd in that it hits in GUP when the page allocator is no
longer active and the context is a syscall. First, is this definitely
the first patch the problem occurs?

Second, it's possible for IRQs to be enabled and an IRQ delivered before
preemption is enabled. It's not clear why that would be a problem other
than lacking symmetry or how it could result in the reported BUG but
might as well rule it out. This is build tested only

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 934d1b5a5449..d0141e51e613 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -192,14 +192,14 @@ static DEFINE_MUTEX(pcp_batch_high_lock);
 
 #define pcpu_spin_unlock(member, ptr)					\
 ({									\
-	spin_unlock(&ptr->member);					\
 	pcpu_task_unpin();						\
+	spin_unlock(&ptr->member);					\
 })
 
 #define pcpu_spin_unlock_irqrestore(member, ptr, flags)			\
 ({									\
-	spin_unlock_irqrestore(&ptr->member, flags);			\
 	pcpu_task_unpin();						\
+	spin_unlock_irqrestore(&ptr->member, flags);			\
 })
 
 /* struct per_cpu_pages specific helpers. */