From: Andrew Morton <akpm@linux-foundation.org>
To: Ye Liu <ye.liu@linux.dev>
Cc: syzbot <syzbot+5f0b6e2e4195c75b5658@syzkaller.appspotmail.com>,
brendan.jackman@linux.dev, hannes@cmpxchg.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
mhocko@suse.com, surenb@google.com,
syzkaller-bugs@googlegroups.com, vbabka@kernel.org,
ziy@nvidia.com, Zhen Ni <zhen.ni@easystack.cn>,
Oscar Salvador <osalvador@suse.de>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [syzbot] [mm?] INFO: rcu detected stall in kvm_vm_release (4)
Date: Thu, 20 Aug 2026 18:20:38 -0700 [thread overview]
Message-ID: <20260820182038.c45e454506c8cd3c1f21930b@linux-foundation.org> (raw)
In-Reply-To: <d477b226-cf6e-4101-9a4a-71c317a891d1@linux.dev>
On Fri, 21 Aug 2026 09:06:48 +0800 Ye Liu <ye.liu@linux.dev> wrote:
> > : The combination of debug tools: KASAN quarantine processing + ORC
> > : unwinder + page_owner stack tracing executed so slowly on the CPU that
> > : it exceeded the RCU stall threshold.
> >
> > (I think we've recently seen the same thing, different callers)
> >
> > I can't say I'm terribly motivated. page_owner is expensive and if you
> > run heavy stress testing with page_owner enabled then such things
> > aren't surprising.
> >
> > Let me Cc a few page_owner and KASAN people, see if they feel
> > differently.
>
> Adding cond_resched() to the qlist_free_all() loop would fix this .
> kasan_quarantine_remove_cache() already dose the same in its scanning loop.
I don't think cond_resched() does what we want for RCU stalls.
And cond_resched() is a no-op without CONFIG_PREEMPT_NONE, which wasn't
set here.
prev parent reply other threads:[~2026-08-21 1:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-20 13:16 [syzbot] [mm?] INFO: rcu detected stall in kvm_vm_release (4) syzbot
2026-08-20 16:29 ` Andrew Morton
2026-08-21 1:06 ` Ye Liu
2026-08-21 1:20 ` Andrew Morton [this message]
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