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 3098CC87FCB for ; Tue, 12 Aug 2025 16:20:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Type:MIME-Version:References:Message-ID:Subject: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=UpB2GIUgkfPcnRjs3ARqM9F7ZHPJ2zjE6ameQ16EUwI=; b=JOEAOIJITGG3GuYfuMlSIE5Ycx XJHWsICrOTpxxTe4uFgPrX/G4VIr6P/w7mI3Bn7YAkwQm1FnS7tHZwJOMJZJY2NvwKvHLI45YuAVq xyNIDBOjFwW9e0oGvCPy+uyVLVdwIjoNccWVukLIbmhbBAfV5bWd5+SLbUVREAGgb30wu2cVnfo09 NfdOIGtzHRB8VXGoFuoZDsYD/2F/XIzSCTIqo6tbVaPoqfWpwZqbDmKQ0Slh352Mj/gFFkxw+nBOa RJIOIIQbAi0anLQ8FitNlgShLVh5FTTaZ2eGfCcwuWFVouQwJLKlQfBYjU0/zTCNRAAz67z+Lel6T EfG0vxOg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ulrjj-0000000BK10-3a97; Tue, 12 Aug 2025 16:20:31 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ulmww-0000000AaCK-0fkP for linux-arm-kernel@lists.infradead.org; Tue, 12 Aug 2025 11:13:51 +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 0FE5225E1; Tue, 12 Aug 2025 04:13:41 -0700 (PDT) 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 5BB453F63F; Tue, 12 Aug 2025 04:13:45 -0700 (PDT) Date: Tue, 12 Aug 2025 12:13:42 +0100 From: Mark Rutland To: Jinjie Ruan Subject: Re: [PATCH -next v7 5/7] arm64: entry: Refactor preempt_schedule_irq() check code Message-ID: References: <20250729015456.3411143-1-ruanjinjie@huawei.com> <20250729015456.3411143-6-ruanjinjie@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250729015456.3411143-6-ruanjinjie@huawei.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250812_041350_285922_8135084D X-CRM114-Status: GOOD ( 26.64 ) 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: , Cc: sstabellini@kernel.org, puranjay@kernel.org, anshuman.khandual@arm.com, catalin.marinas@arm.com, liaochang1@huawei.com, oleg@redhat.com, kristina.martsenko@arm.com, linux-kernel@vger.kernel.org, broonie@kernel.org, chenl311@chinatelecom.cn, xen-devel@lists.xenproject.org, leitao@debian.org, ryan.roberts@arm.com, akpm@linux-foundation.org, mbenes@suse.cz, will@kernel.org, ardb@kernel.org, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jul 29, 2025 at 09:54:54AM +0800, Jinjie Ruan wrote: > ARM64 requires an additional check whether to reschedule on return > from interrupt. So add arch_irqentry_exit_need_resched() as the default > NOP implementation and hook it up into the need_resched() condition in > raw_irqentry_exit_cond_resched(). This allows ARM64 to implement > the architecture specific version for switching over to > the generic entry code. > > To align the structure of the code with irqentry_exit_cond_resched() > from the generic entry code, hoist the need_irq_preemption() > and IS_ENABLED() check earlier. And different preemption check functions > are defined based on whether dynamic preemption is enabled. > > Suggested-by: Mark Rutland > Suggested-by: Kevin Brodsky > Suggested-by: Thomas Gleixner > Signed-off-by: Jinjie Ruan > --- > arch/arm64/include/asm/preempt.h | 4 ++++ > arch/arm64/kernel/entry-common.c | 35 ++++++++++++++++++-------------- > kernel/entry/common.c | 16 ++++++++++++++- > 3 files changed, 39 insertions(+), 16 deletions(-) Can you please split the change to kernel/entry/common.c into a separate patch? That doesn't depend on the arm64-specific changes, and it'll make it easier to handle any conflcits when merging this. Mark. > > diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h > index 0159b625cc7f..0f0ba250efe8 100644 > --- a/arch/arm64/include/asm/preempt.h > +++ b/arch/arm64/include/asm/preempt.h > @@ -85,6 +85,7 @@ static inline bool should_resched(int preempt_offset) > void preempt_schedule(void); > void preempt_schedule_notrace(void); > > +void raw_irqentry_exit_cond_resched(void); > #ifdef CONFIG_PREEMPT_DYNAMIC > > DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); > @@ -92,11 +93,14 @@ void dynamic_preempt_schedule(void); > #define __preempt_schedule() dynamic_preempt_schedule() > void dynamic_preempt_schedule_notrace(void); > #define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace() > +void dynamic_irqentry_exit_cond_resched(void); > +#define irqentry_exit_cond_resched() dynamic_irqentry_exit_cond_resched() > > #else /* CONFIG_PREEMPT_DYNAMIC */ > > #define __preempt_schedule() preempt_schedule() > #define __preempt_schedule_notrace() preempt_schedule_notrace() > +#define irqentry_exit_cond_resched() raw_irqentry_exit_cond_resched() > > #endif /* CONFIG_PREEMPT_DYNAMIC */ > #endif /* CONFIG_PREEMPTION */ > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > index 7c2299c1ba79..4f92664fd46c 100644 > --- a/arch/arm64/kernel/entry-common.c > +++ b/arch/arm64/kernel/entry-common.c > @@ -285,19 +285,8 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs, > lockdep_hardirqs_on(CALLER_ADDR0); > } > > -#ifdef CONFIG_PREEMPT_DYNAMIC > -DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); > -#define need_irq_preemption() \ > - (static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched)) > -#else > -#define need_irq_preemption() (IS_ENABLED(CONFIG_PREEMPTION)) > -#endif > - > static inline bool arm64_preempt_schedule_irq(void) > { > - if (!need_irq_preemption()) > - return false; > - > /* > * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC > * priority masking is used the GIC irqchip driver will clear DAIF.IF > @@ -672,6 +661,24 @@ static __always_inline void __el1_pnmi(struct pt_regs *regs, > arm64_exit_nmi(regs, state); > } > > +void raw_irqentry_exit_cond_resched(void) > +{ > + if (!preempt_count()) { > + if (need_resched() && arm64_preempt_schedule_irq()) > + preempt_schedule_irq(); > + } > +} > + > +#ifdef CONFIG_PREEMPT_DYNAMIC > +DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); > +void dynamic_irqentry_exit_cond_resched(void) > +{ > + if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched)) > + return; > + raw_irqentry_exit_cond_resched(); > +} > +#endif > + > static __always_inline void __el1_irq(struct pt_regs *regs, > void (*handler)(struct pt_regs *)) > { > @@ -681,10 +688,8 @@ static __always_inline void __el1_irq(struct pt_regs *regs, > do_interrupt_handler(regs, handler); > irq_exit_rcu(); > > - if (!preempt_count() && need_resched()) { > - if (arm64_preempt_schedule_irq()) > - preempt_schedule_irq(); > - } > + if (IS_ENABLED(CONFIG_PREEMPTION)) > + irqentry_exit_cond_resched(); > > exit_to_kernel_mode(regs, state); > } > diff --git a/kernel/entry/common.c b/kernel/entry/common.c > index b82032777310..4aa9656fa1b4 100644 > --- a/kernel/entry/common.c > +++ b/kernel/entry/common.c > @@ -142,6 +142,20 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs) > return ret; > } > > +/** > + * arch_irqentry_exit_need_resched - Architecture specific need resched function > + * > + * Invoked from raw_irqentry_exit_cond_resched() to check if need resched. > + * Defaults return true. > + * > + * The main purpose is to permit arch to skip preempt a task from an IRQ. > + */ > +static inline bool arch_irqentry_exit_need_resched(void); > + > +#ifndef arch_irqentry_exit_need_resched > +static inline bool arch_irqentry_exit_need_resched(void) { return true; } > +#endif > + > void raw_irqentry_exit_cond_resched(void) > { > if (!preempt_count()) { > @@ -149,7 +163,7 @@ void raw_irqentry_exit_cond_resched(void) > rcu_irq_exit_check_preempt(); > if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) > WARN_ON_ONCE(!on_thread_stack()); > - if (need_resched()) > + if (need_resched() && arch_irqentry_exit_need_resched()) > preempt_schedule_irq(); > } > } > -- > 2.34.1 >