From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AFB8AD60; Tue, 28 Nov 2023 06:41:02 -0800 (PST) Received: from mail.maildlp.com (unknown [172.18.186.231]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4SflQ45R4nz6J6v1; Tue, 28 Nov 2023 22:36:28 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id E3876140682; Tue, 28 Nov 2023 22:41:00 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Tue, 28 Nov 2023 14:41:00 +0000 Date: Tue, 28 Nov 2023 14:40:59 +0000 From: Jonathan Cameron To: Russell King CC: , , , , , , , , , , , , , Salil Mehta , Jean-Philippe Brucker , , , James Morse , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Subject: Re: [PATCH RFC 02/22] x86: intel_epb: Don't rely on link order Message-ID: <20231128144059.000042c8@Huawei.com> In-Reply-To: References: Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml500006.china.huawei.com (7.191.161.198) To lhrpeml500005.china.huawei.com (7.191.163.240) On Tue, 07 Nov 2023 10:29:28 +0000 Russell King wrote: > From: James Morse > > intel_epb_init() is called as a subsys_initcall() to register cpuhp > callbacks. The callbacks make use of get_cpu_device() which will return > NULL unless register_cpu() has been called. register_cpu() is called > from topology_init(), which is also a subsys_initcall(). > > This is fragile. Moving the register_cpu() to a different > subsys_initcall() leads to a NULL dereference during boot. > > Make intel_epb_init() a late_initcall(), user-space can't provide a > policy before this point anyway. > > Signed-off-by: James Morse > Signed-off-by: Russell King (Oracle) Seems reasonable. FWIW Reviewed-by: Jonathan Cameron > --- > subsys_initcall_sync() would be an option, but moving the register_cpu() > calls into ACPI also means adding a safety net for CPUs that are online > but not described properly by firmware. This lives in subsys_initcall_sync(). > --- > arch/x86/kernel/cpu/intel_epb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/intel_epb.c b/arch/x86/kernel/cpu/intel_epb.c > index e4c3ba91321c..f18d35fe27a9 100644 > --- a/arch/x86/kernel/cpu/intel_epb.c > +++ b/arch/x86/kernel/cpu/intel_epb.c > @@ -237,4 +237,4 @@ static __init int intel_epb_init(void) > cpuhp_remove_state(CPUHP_AP_X86_INTEL_EPB_ONLINE); > return ret; > } > -subsys_initcall(intel_epb_init); > +late_initcall(intel_epb_init);