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From: Qian Cai <cai@lca.pw>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org
Subject: Re: splice() rcu_sched self-detected stall on CPU
Date: Tue, 5 May 2020 15:00:34 -0400	[thread overview]
Message-ID: <8678900D-8D52-4195-A767-9E6923EE0AAF@lca.pw> (raw)
In-Reply-To: <20200505185732.GP2869@paulmck-ThinkPad-P72>



> On May 5, 2020, at 2:57 PM, Paul E. McKenney <paulmck@kernel.org> wrote:
> 
> On Mon, May 04, 2020 at 03:11:09PM -0400, Qian Cai wrote:
>> Running a syscall fuzzer inside a container on linux-next floods systems with soft lockups. It looks like stuck in this line at iov_iter_copy_from_user_atomic(), Thoughts?
>> 
>> iterate_all_kinds(i, bytes, v,
>>                copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
>>                memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
>>                                 v.bv_offset, v.bv_len),
>>                memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
>>        )
> 
> If the size being copied is large enough, something like this might happen.
> 
> Is this a CONFIG_PREEMPT=n kernel?  And is the size passed in to

Yes, CONFIG_PREEMPT=n.

> iov_iter_copy_from_user_atomic() quite large, given that this is generated
> by a fuzzer?  If so, one thing to try is to add cond_resched() in the
> iterate_bvec(), iterate_kvec(), and iterate_iovec() macros.

I’ll try that.

  reply	other threads:[~2020-05-05 19:00 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-04 19:11 Qian Cai
2020-05-05 18:57 ` Paul E. McKenney
2020-05-05 19:00   ` Qian Cai [this message]
2020-07-20 20:12     ` Qian Cai
2020-07-20 22:10       ` Paul E. McKenney

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