From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18FE1E748FC for ; Mon, 2 Oct 2023 17:26:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229572AbjJBR0K (ORCPT ); Mon, 2 Oct 2023 13:26:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38534 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229590AbjJBR0H (ORCPT ); Mon, 2 Oct 2023 13:26:07 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3192CAC for ; Mon, 2 Oct 2023 10:26:03 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6D5FEC15; Mon, 2 Oct 2023 10:26:41 -0700 (PDT) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.28.139]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 238FA3F59C; Mon, 2 Oct 2023 10:26:01 -0700 (PDT) Date: Mon, 2 Oct 2023 18:25:58 +0100 From: Mark Rutland To: Douglas Anderson Cc: Catalin Marinas , Will Deacon , Marc Zyngier , Stephen Boyd , Valentin Schneider , Chen-Yu Tsai , D Scott Phillips , Josh Poimboeuf , Peter Zijlstra , Sumit Garg , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] arm64: smp: Don't directly call arch_smp_send_reschedule() for wakeup Message-ID: References: <20231002094526.1.Ie8f760213053e3d11592f892b30912dbac6b8b48@changeid> <20231002094526.2.I2e6d22fc42ccbf6b26465a28a10e36e05ccf3075@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231002094526.2.I2e6d22fc42ccbf6b26465a28a10e36e05ccf3075@changeid> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 02, 2023 at 09:45:30AM -0700, Douglas Anderson wrote: > In commit 2b2d0a7a96ab ("arm64: smp: Remove dedicated wakeup IPI") we > started using a scheduler IPI to avoid a dedicated reschedule. When we > did this, we used arch_smp_send_reschedule() directly rather than > calling smp_send_reschedule(). The only difference is that calling > arch_smp_send_reschedule() directly avoids tracing. Presumably we > _don't_ want to avoid tracing here, so switch to > smp_send_reschedule(). > > Fixes: 2b2d0a7a96ab ("arm64: smp: Remove dedicated wakeup IPI") > Signed-off-by: Douglas Anderson > --- > I don't 100% know if this is correct and I don't have any hardware > that uses the "ACPI parking protocol", but I think it's right. My main > incentive for this is that it makes it easier to backport pseudo-NMI > to kernels that don't have arch_smp_send_reschedule(), but I think > it's also more correct. > > If for some reason we truly did want to avoid tracing here, please > shout and we can drop this patch. This should be sound, and I don't have strong feelings either way on this, so FWIW: Acked-by: Mark Rutland Mark. > > arch/arm64/kernel/smp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index 0a6002243a8c..b530d8ef9c1d 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -1063,7 +1063,7 @@ void arch_send_wakeup_ipi(unsigned int cpu) > * We use a scheduler IPI to wake the CPU as this avoids the need for a > * dedicated IPI and we can safely handle spurious scheduler IPIs. > */ > - arch_smp_send_reschedule(cpu); > + smp_send_reschedule(cpu); > } > #endif > > -- > 2.42.0.582.g8ccd20d70d-goog >