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Subject: Re: [PATCH] MIPS: IRQ Stack: Unwind IRQ stack onto task stack
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From: Matt Redfearn <matt.redfearn@imgtec.com>
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Date: Tue, 4 Apr 2017 13:18:58 +0100
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To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org, Paolo Bonzini <pbonzini@redhat.com>, Marcin Nowakowski <marcin.nowakowski@imgtec.com>, Masanari Iida <standby24x7@gmail.com>, Chris Metcalf <cmetcalf@mellanox.com>, LKML <linux-kernel@vger.kernel.org>, James Hogan <james.hogan@imgtec.com>, Paul Burton <paul.burton@imgtec.com>, Ingo Molnar <mingo@kernel.org>, Andrew Morton <akpm@linux-foundation.org>
Message-ID: <20170404121858.DDDBsSElitM6ubReZtOVKTG4C9TzYHO3azW0IlYS-p8@z>

Hi Jason,


On 04/04/17 12:58, Jason A. Donenfeld wrote:
> This indeed is useful. Out of curiosity, are other archs using a
> similar technique? In anycase,
>
> Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>

Yes, at least x86 and ARM64 do the same thing (probably more)

x86 saves the previous stack pointer on the IRQ stack in 
http://lxr.free-electrons.com/source/arch/x86/kernel/irq_32.c#L70
which is then unwound in 
http://lxr.free-electrons.com/source/arch/x86/kernel/dumpstack.c#L51

ARM64 saves the task SP in 
http://lxr.free-electrons.com/source/arch/arm64/kernel/entry.S#L249
And unwinds it in 
http://lxr.free-electrons.com/source/arch/arm64/kernel/traps.c#L140

Thanks,
Matt