Re: [PATCH 01/25] xor: assert that xor_blocks is not called from interrupt context

Peter Zijlstra <[email protected]> Fri, 27 Feb 2026 15:24:55 +0100

Newsgroups	gmane.linux.ports.riscv,gmane.linux.ports.alpha,gmane.linux.kernel,gmane.linux.ports.arm.kernel,gmane.linux.ports.ppc64.devel,gmane.linux.ports.sparc,gmane.linux.uml.devel,gmane.linux.kernel.cryptoapi,gmane.comp.file-systems.btrfs,gmane.linux.kernel.cross-arch,gmane.linux.raid
Message-ID	<[email protected]>

On Thu, Feb 26, 2026 at 07:10:13AM -0800, Christoph Hellwig wrote:
> Most of the optimized xor_blocks versions require FPU/vector registers,
> which generally are not supported in interrupt context.
> 
> Both callers already are in user context, so enforce this at the highest
> level.
> 
> Signed-off-by: Christoph Hellwig <[email protected]>
> ---
>  crypto/xor.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/crypto/xor.c b/crypto/xor.c
> index f39621a57bb3..864f3604e867 100644
> --- a/crypto/xor.c
> +++ b/crypto/xor.c
> @@ -28,6 +28,8 @@ xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
>  {
>  	unsigned long *p1, *p2, *p3, *p4;
>  
> +	WARN_ON_ONCE(in_interrupt());

Your changelog makes it sound like you want:

	WARN_ON_ONCE(!in_task());

But perhaps something like so:

	lockdep_assert_preempt_enabled();

Would do? That ensures we are in preemptible context, which is much the
same. That also ensures the cost of this assertion is only paid on debug
kernels.


>  	p1 = (unsigned long *) srcs[0];
>  	if (src_count == 1) {
>  		active_template->do_2(bytes, dest, p1);
> -- 
> 2.47.3
>