From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chen Yu Subject: Re: [PATCH 2/4][RFC v2] PM / sleep: Introduce arch-specific hook for disable/enable nonboot cpus Date: Sun, 9 Oct 2016 00:58:43 +0800 Message-ID: <20161008165843.GB24225@sharon> References: <8f0aeb0a-5e72-8327-2406-a78ad783f6f2@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <8f0aeb0a-5e72-8327-2406-a78ad783f6f2@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Andy Lutomirski Cc: linux-pm@vger.kernel.org, x86@kernel.org, "Rafael J. Wysocki" , Len Brown , Peter Zijlstra , "H. Peter Anvin" , Borislav Petkov , Pavel Machek , Brian Gerst , Thomas Gleixner , Ingo Molnar , Varun Koyyalagunta , linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org Hi Andy, On Fri, Oct 07, 2016 at 12:31:41PM -0700, Andy Lutomirski wrote: > On 06/25/2016 09:18 AM, Chen Yu wrote: > >There is requirement that we need to do some arch-specific > >operations before putting the nonboot CPUs offline/online. > >One of the requirements comes from the hibernation resume > >process on x86_64, we need to kick all the offlin-CPUs > >online and offline again, in order to put them in a safe > >state, thus to avoid possible unwilling wake up during > >hibernation resume. > > > >Signed-off-by: Chen Yu > >--- > > kernel/cpu.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > >diff --git a/kernel/cpu.c b/kernel/cpu.c > >index d25266e..ce6e5e4 100644 > >--- a/kernel/cpu.c > >+++ b/kernel/cpu.c > >@@ -1017,6 +1017,16 @@ EXPORT_SYMBOL_GPL(cpu_up); > > #ifdef CONFIG_PM_SLEEP_SMP > > static cpumask_var_t frozen_cpus; > > > >+void __weak arch_disable_nonboot_cpus_pre(void) > > I don't like using __weak. It penalizes code size on architectures that > don't hook these functions. My preferred pattern is: > > include/linux/something.h: > > #include > > #ifndef arch_do_xyz > static inline void arch_do_xyz() {} > #endif > > arch/whatever/asm/something.h: > > extern void arch_do_xyz(); /* or static inline... */ > #define arch_do_xyz > > > This is totally free for architectures that don't have the hooks and it can > potentially be inlined on architectures that do have the hooks. Everyone > wins except that it's about five additional lines of code. > Thanks for your guidance, this patch was deprecated previously, but I'll take your advice the next time when writing similar patch. > --Andy Thanks, Yu