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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 84A59C0219D for ; Mon, 10 Feb 2025 11:45:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ZR/U7aoKXyMToJmd6a+gi9jp0U5/yih3/l97CmMQipU=; b=TwfDdM6PnJo3ruJIlnRwogbBTx XPD1zo1dfioW1hyDMyJS0dK97sBVabWBOKGaDZzRVH9hUUHfmUSnqSvdKbYHjdpYSqOMSIccON2D0 yfq/XhoVUqy+OKknEoOiPqyeuzNdWaexpuBk25n2SwVz0dJoqk5MNkPgQwKqunigGpD7tPcnwop/0 R4kcHZ0OnmgYaWaFvl2VGf9+kFC5NKGkISXfMk/Y8FNCMqU6XzFLMnJARVc+dFIuO05yv8Z7kPkUp nCK8r/rKfqlkFn36RgVqGyitSGTQdx1QFdqFNWxGg0zZ4RPCYMAOXr59jERJSnHTPSK+opwJlo0Su JLXP2toQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1thSEL-0000000HHcb-02Ft; Mon, 10 Feb 2025 11:45:37 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1thS2T-0000000HEUh-0CPZ for linux-arm-kernel@lists.infradead.org; Mon, 10 Feb 2025 11:33:22 +0000 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 95BD41007; Mon, 10 Feb 2025 03:33:38 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0DC243F5A1; Mon, 10 Feb 2025 03:33:09 -0800 (PST) Date: Mon, 10 Feb 2025 11:33:07 +0000 From: Mark Rutland To: Jinjie Ruan Cc: catalin.marinas@arm.com, will@kernel.org, oleg@redhat.com, sstabellini@kernel.org, tglx@linutronix.de, peterz@infradead.org, luto@kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kees@kernel.org, wad@chromium.org, akpm@linux-foundation.org, samitolvanen@google.com, masahiroy@kernel.org, hca@linux.ibm.com, aliceryhl@google.com, rppt@kernel.org, xur@google.com, paulmck@kernel.org, arnd@arndb.de, mbenes@suse.cz, puranjay@kernel.org, pcc@google.com, ardb@kernel.org, sudeep.holla@arm.com, guohanjun@huawei.com, rafael@kernel.org, liuwei09@cestc.cn, dwmw@amazon.co.uk, Jonathan.Cameron@huawei.com, liaochang1@huawei.com, kristina.martsenko@arm.com, ptosi@google.com, broonie@kernel.org, thiago.bauermann@linaro.org, kevin.brodsky@arm.com, joey.gouly@arm.com, liuyuntao12@huawei.com, leobras@redhat.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, xen-devel@lists.xenproject.org Subject: Re: [PATCH -next v5 04/22] arm64: entry: Rework arm64_preempt_schedule_irq() Message-ID: References: <20241206101744.4161990-1-ruanjinjie@huawei.com> <20241206101744.4161990-5-ruanjinjie@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241206101744.4161990-5-ruanjinjie@huawei.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250210_033321_177062_2F48327F X-CRM114-Status: GOOD ( 23.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Dec 06, 2024 at 06:17:26PM +0800, Jinjie Ruan wrote: > The generic entry do preempt_schedule_irq() by checking if need_resched() > satisfied, but arm64 has some of its own additional checks such as > GIC priority masking. > > In preparation for moving arm64 over to the generic entry code, rework > arm64_preempt_schedule_irq() to check whether it need resched in a check > function called arm64_need_resched(). I think what this is saying is that the generic entry code has the form: | raw_irqentry_exit_cond_resched() | { | if (!preempt_count()) { | ... | if (need_resched()) | preempt_schedule_irq(); | } | } ... but it's not obvious why it's better to have and arm64_need_resched() rather than a arm64_preempt_schedule_irq(). Having some idea of the change you intend to make to the generic code would be helpful, and/or that generic change should be made earlier as a preparatory patch. Mark. > No functional changes. > > Signed-off-by: Jinjie Ruan > --- > arch/arm64/kernel/entry-common.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > index 7a588515ee07..da68c089b74b 100644 > --- a/arch/arm64/kernel/entry-common.c > +++ b/arch/arm64/kernel/entry-common.c > @@ -83,10 +83,10 @@ DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); > #define need_irq_preemption() (IS_ENABLED(CONFIG_PREEMPTION)) > #endif > > -static void __sched arm64_preempt_schedule_irq(void) > +static inline bool arm64_need_resched(void) > { > if (!need_irq_preemption()) > - return; > + return false; > > /* > * Note: thread_info::preempt_count includes both thread_info::count > @@ -94,7 +94,7 @@ static void __sched arm64_preempt_schedule_irq(void) > * preempt_count(). > */ > if (READ_ONCE(current_thread_info()->preempt_count) != 0) > - return; > + return false; > > /* > * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC > @@ -103,7 +103,7 @@ static void __sched arm64_preempt_schedule_irq(void) > * DAIF we must have handled an NMI, so skip preemption. > */ > if (system_uses_irq_prio_masking() && read_sysreg(daif)) > - return; > + return false; > > /* > * Preempting a task from an IRQ means we leave copies of PSTATE > @@ -113,8 +113,10 @@ static void __sched arm64_preempt_schedule_irq(void) > * Only allow a task to be preempted once cpufeatures have been > * enabled. > */ > - if (system_capabilities_finalized()) > - preempt_schedule_irq(); > + if (!system_capabilities_finalized()) > + return false; > + > + return true; > } > > /* > @@ -139,7 +141,8 @@ static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs, > return; > } > > - arm64_preempt_schedule_irq(); > + if (arm64_need_resched()) > + preempt_schedule_irq(); > > trace_hardirqs_on(); > } else { > -- > 2.34.1 >