linux-kernel - Re: [PATCH 2/4][RFC v2] PM / sleep: Introduce arch-specific hook for disable/enable nonboot cpus

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20161008165843.GB24225@sharon>
Date:   Sun, 9 Oct 2016 00:58:43 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     linux-pm@...r.kernel.org, x86@...nel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
        Pavel Machek <pavel@....cz>, Brian Gerst <brgerst@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Varun Koyyalagunta <cpudebug@...ttech.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4][RFC v2] PM / sleep: Introduce arch-specific hook for
 disable/enable nonboot cpus

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 <yu.c.chen@...el.com>
> >---
> > 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 <asm/something.h>
> 
> #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