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Date:   Mon, 19 Jul 2021 13:38:51 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Russell King Oracle <linux@armlinux.org.uk>
Cc:     hch@lst.de, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, James.Bottomley@hansenpartnership.com,
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        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
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Subject: Re: flush_kernel_dcache_page fixes and removal
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Russell King Oracle <linux@armlinux.org.uk> wrote:
>
> I think you need to be careful - I seem to have a recollection that the
> reason we ended up with flush_kernel_dcache_page() was the need to avoid
> the taking of the mmap lock for 32-bit ARM VIVT based CPUs in
> flush_dcache_page(). 32-bit ARM flush_dcache_page() can block.
> 
> If you're sure that all these changes you're making do not end up
> calling flush_dcache_page() from a path where we are atomic, then fine.

The Crypto API has been calling flush_dcache_page from softirq
context since before the advent of git (see crypto/scatterwalk.c
from the initial import).  So if 32-bit ARM blocks on it then this
has been broken for almost 20 years.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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