From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 55FD915FD13 for ; Fri, 7 Feb 2025 06:51:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=114.242.206.163 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738911079; cv=none; b=dfOgsM43V/DSZ+hRANe1I6l4SpM5hyCtbVyymClHMOMe15x82U2FQQc+bzlA2iVdWSg6aO5CGKeSDm+1LwwZDvnaHGyOhAbFW4GxSJPJyVDRiPVq6drRdqv9/MrRtfPfGT7sRtDd5Ttpp6PmpiiLQckhbA83ZR0cUg+HomKkCOE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738911079; c=relaxed/simple; bh=XOkEWq88HxMGa4q3w3xKhtQkrwRH5QJR3PKEJmTEirI=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=Xp9ylfEZ3qkfCknl427pzbs0479o9Xyw4LF2jYgzlbOZonp2Rs+BpJxQ2tcnCu6lIvaUrRoqhwdhtgxYJ8r/KWhZmNg4/JC5vwSsBVJ5nadws/iIHzI1/fSsltefHr0Xi0/5u/V6SxnikxCsr+T56t1Syo+zQpjlbTu+UGO+oME= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn; spf=pass smtp.mailfrom=loongson.cn; arc=none smtp.client-ip=114.242.206.163 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=loongson.cn Received: from loongson.cn (unknown [10.20.42.62]) by gateway (Coremail) with SMTP id _____8Dx_3NiraVnkk9uAA--.29335S3; Fri, 07 Feb 2025 14:51:14 +0800 (CST) Received: from [10.20.42.62] (unknown [10.20.42.62]) by front1 (Coremail) with SMTP id qMiowMDxH+VfraVnT+YDAA--.16729S3; Fri, 07 Feb 2025 14:51:11 +0800 (CST) Subject: Re: [PATCH] loongson: Fix idle VS timer enqueue To: Marco Crivellari , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Huacai Chen , WANG Xuerui , Tiezhu Yang , Frederic Weisbecker , Peter Zijlstra , Jiaxun Yang References: <20250206162922.3028861-1-marco.crivellari@suse.com> <20250206162922.3028861-2-marco.crivellari@suse.com> From: bibo mao Message-ID: Date: Fri, 7 Feb 2025 14:50:39 +0800 User-Agent: Mozilla/5.0 (X11; Linux loongarch64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20250206162922.3028861-2-marco.crivellari@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-CM-TRANSID:qMiowMDxH+VfraVnT+YDAA--.16729S3 X-CM-SenderInfo: xpdruxter6z05rqj20fqof0/ X-Coremail-Antispam: 1Uk129KBj93XoWxZF47Xr47ur1DCrW8tFWkAFc_yoWrKw1fpr yfuwn8KrsYgrn3X347tw18ur98u34DGa1a9anxArW8AF4jvr10qr1kt34kW3ZYg3y8Gw1F vF1rXa42g3WUA3XCm3ZEXasCq-sJn29KB7ZKAUJUUUUx529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUP0b4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_ GcCE3s1ln4kS14v26r126r1DM2AIxVAIcxkEcVAq07x20xvEncxIr21l57IF6xkI12xvs2 x26I8E6xACxx1l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r126r1D McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lc7 I2V7IY0VAS07AlzVAYIcxG8wCY1x0262kKe7AKxVWUAVWUtwCF04k20xvY0x0EwIxGrwCF x2IqxVCFs4IE7xkEbVWUJVW8JwCFI7km07C267AKxVWUAVWUtwC20s026c02F40E14v26r 1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij 64vIr41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Jr 0_Gr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF 0xvEx4A2jsIEc7CjxVAFwI0_Jr0_GrUvcSsGvfC2KfnxnUUI43ZEXa7IU8Dl1DUUUUU== yes, it had better skip out inner loop and let idle framework handle it. Tested-by: Bibo Mao On 2025/2/7 上午12:29, Marco Crivellari wrote: > From: Peter Zijlstra > > Loongson re-enables interrupts on its idle routine and performs a > TIF_NEED_RESCHED check afterwards before putting the CPU to sleep. > > The IRQs firing between the check and the idling instruction may set the > TIF_NEED_RESCHED flag. In order to deal with the such a race, IRQs > interrupting __arch_cpu_idle() rollback their return address to the > beginning of __arch_cpu_idle() so that TIF_NEED_RESCHED is checked > again before going back to sleep. > > However idle IRQs can also queue timers that may require a tick > reprogramming through a new generic idle loop iteration but those timers > would go unnoticed here because __arch_cpu_idle() only checks > TIF_NEED_RESCHED. It doesn't check for pending timers. > > Fix this with fast-forwarding idle IRQs return value to the end of the > idle routine instead of the beginning, so that the generic idle loop > handles both TIF_NEED_RESCHED and pending timers. > > Fixes: 0603839b18f4 ("LoongArch: Add exception/interrupt handling") > Not-yet-signed-off-by: Peter Zijlstra > Cc: WANG Xuerui > Signed-off-by: Frederic Weisbecker > Signed-off-by: Marco Crivellari > --- > arch/loongarch/kernel/genex.S | 33 +++++++++++++++++++-------------- > arch/loongarch/kernel/idle.c | 3 +-- > arch/loongarch/kernel/reset.c | 23 ++++++++++++++--------- > 3 files changed, 34 insertions(+), 25 deletions(-) > > diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S > index 86d5d90ebefe..ab2e9a262ee2 100644 > --- a/arch/loongarch/kernel/genex.S > +++ b/arch/loongarch/kernel/genex.S > @@ -18,28 +18,33 @@ > > .align 5 > SYM_FUNC_START(__arch_cpu_idle) > - /* start of rollback region */ > - LONG_L t0, tp, TI_FLAGS > - nop > - andi t0, t0, _TIF_NEED_RESCHED > - bnez t0, 1f > - nop > - nop > - nop > + /* start of idle interrupt region */ > + li.w t0, CSR_CRMD_IE > + /* idle instruction needs irq enabled */ > + csrxchg t0, t0, LOONGARCH_CSR_CRMD > + /* > + * If an interrupt lands here; between enabling interrupts above and > + * going idle on the next instruction, we must *NOT* go idle since the > + * interrupt could have set TIF_NEED_RESCHED or caused an timer to need > + * reprogramming. Fall through -- see handle_vint() below -- and have > + * the idle loop take care of things. > + */ > idle 0 > - /* end of rollback region */ > -1: jr ra > + nop > + /* end of idle interrupt region */ > +SYM_INNER_LABEL(__arch_cpu_idle_exit, SYM_L_LOCAL) > + jr ra > SYM_FUNC_END(__arch_cpu_idle) > > SYM_CODE_START(handle_vint) > UNWIND_HINT_UNDEFINED > BACKUP_T0T1 > SAVE_ALL > - la_abs t1, __arch_cpu_idle > + la_abs t1, __arch_cpu_idle_exit > LONG_L t0, sp, PT_ERA > - /* 32 byte rollback region */ > - ori t0, t0, 0x1f > - xori t0, t0, 0x1f > + /* 16 byte idle interrupt region */ > + ori t0, t0, 0x0f > + addi.d t0, t0, 1 > bne t0, t1, 1f > LONG_S t0, sp, PT_ERA > 1: move a0, sp > diff --git a/arch/loongarch/kernel/idle.c b/arch/loongarch/kernel/idle.c > index 0b5dd2faeb90..54b247d8cdb6 100644 > --- a/arch/loongarch/kernel/idle.c > +++ b/arch/loongarch/kernel/idle.c > @@ -11,7 +11,6 @@ > > void __cpuidle arch_cpu_idle(void) > { > - raw_local_irq_enable(); > - __arch_cpu_idle(); /* idle instruction needs irq enabled */ > + __arch_cpu_idle(); > raw_local_irq_disable(); > } > diff --git a/arch/loongarch/kernel/reset.c b/arch/loongarch/kernel/reset.c > index 1ef8c6383535..d78e8a1064a1 100644 > --- a/arch/loongarch/kernel/reset.c > +++ b/arch/loongarch/kernel/reset.c > @@ -20,6 +20,11 @@ > void (*pm_power_off)(void); > EXPORT_SYMBOL(pm_power_off); > > +static __always_inline void native_halt(void) > +{ > + asm volatile("idle 0" : : : "memory"); > +} > + > void machine_halt(void) > { > #ifdef CONFIG_SMP > @@ -32,9 +37,9 @@ void machine_halt(void) > pr_notice("\n\n** You can safely turn off the power now **\n\n"); > console_flush_on_panic(CONSOLE_FLUSH_PENDING); > > - while (true) { > - __arch_cpu_idle(); > - } > + while (1) { > + native_halt(); > + }; > } > > void machine_power_off(void) > @@ -52,9 +57,9 @@ void machine_power_off(void) > efi.reset_system(EFI_RESET_SHUTDOWN, EFI_SUCCESS, 0, NULL); > #endif > > - while (true) { > - __arch_cpu_idle(); > - } > + while (1) { > + native_halt(); > + }; > } > > void machine_restart(char *command) > @@ -73,7 +78,7 @@ void machine_restart(char *command) > if (!acpi_disabled) > acpi_reboot(); > > - while (true) { > - __arch_cpu_idle(); > - } > + while (1) { > + native_halt(); > + }; > } >