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From: Edward Adam Davis <eadavis@qq.com>
To: herbert@gondor.apana.org.au
Cc: davem@davemloft.net,
	eadavis@qq.com,
	linux-crypto@vger.kernel.org,
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	olivia@selenic.com,
	syzbot+c52ab18308964d248092@syzkaller.appspotmail.com,
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Subject: Re: [PATCH] hwrng: core - fix task hung in hwrng_fillfn
Date: Fri,  1 Dec 2023 20:34:12 +0800
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On Fri, 1 Dec 2023 19:41:11 +0800, Herbert Xu wrote:
> >
> > Reduce the scope of critical zone protection.
> > The original critical zone contains a too large range, especially like
> > copy_to_user() should not be included in the critical zone.
> 
> Which part in particular is taking 143 seconds? The buffer is
> only 128 bytes long.  Why is a 128-byte copy taking 143 seconds,
> even with a page fault?
According to splat, after a page fault occurred, the attempt to retrieve 
rcu_read_lock() failed, resulting in a timeout of 143s. This is my speculation.

Edward