linux-kernel - Re: [PATCH] x86: don't ever patch back to UP if we unplug 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: <20120802082357.GA3574@gmail.com>
Date:	Thu, 2 Aug 2012 10:23:57 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
	Paul McKenney <paul.mckenney@...ibm.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH] x86: don't ever patch back to UP if we unplug cpus.


* Rusty Russell <rusty@...tcorp.com.au> wrote:

> Paul McKenney points out:
> 
>  mean offline overhead is 6251/48=130.2 milliseconds.
> 
>  If I remove the alternatives_smp_switch() from the offline
>  path [...] the mean offline overhead is 550/42=13.1 milliseconds
> 
> Basically, we're never going to get those 120ms back, and the code is
> pretty messy.
> 
> We get rid of:
> 1) The "smp-alt-once" boot option.  It's actually "smp-alt-boot", the
>    documentation is wrong.  It's now the default.
> 2) The skip_smp_alternatives flag used by suspend.
> 3) arch_disable_nonboot_cpus_begin() and arch_disable_nonboot_cpus_end()
>    which were only used to set this one flag.
> 
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> ---
>  Documentation/kernel-parameters.txt |    3 -
>  arch/x86/include/asm/alternative.h  |    4 -
>  arch/x86/kernel/alternative.c       |  104 +++++++-----------------------------
>  arch/x86/kernel/smpboot.c           |   20 ------
>  kernel/cpu.c                        |   11 ---
>  5 files changed, 27 insertions(+), 115 deletions(-)

triggers this build failure:

 arch/x86/kernel/alternative.c:507:36: error: ‘setup_max_cpus’ undeclared (first use in this function)
 arch/x86/kernel/alternative.c:508:3: error: ‘uniproc_patched’ undeclared (first use in this function)

on the attached UP config.

Thanks,

	Ingo

View attachment "config" of type "text/plain" (74121 bytes)