From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Huang Rui <ray.huang@amd.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
spg_linux_kernel@amd.com, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] x86/delay: Do not use cpu_tss in preemptible ctxt in delay_mwaitx()
Date: Wed, 9 Mar 2016 19:10:03 +0100 [thread overview]
Message-ID: <20160309181003.GF6564@pd.tnic> (raw)
In-Reply-To: <CALCETrVGaPASf=r7Z3aSQ1aM7EmHfT1y5QBK6Gss-M=++D+wUw@mail.gmail.com>
On Wed, Mar 09, 2016 at 09:56:39AM -0800, Andy Lutomirski wrote:
> On Mar 9, 2016 3:38 AM, "Borislav Petkov" <bp@alien8.de> wrote:
> >
> > From: Borislav Petkov <bp@suse.de>
> >
> > So Andy had a good idea about using a cacheline-aligned, seldomly used
> > per-cpu var as the MONITORX target but we can't use it in preemptible
> > context. The first simple idea I have is to disable preemption around us
> > dereffing it.
>
> What's the actual problem? Is it the preempt warnings and, if so,
> would raw_cpu_ptr fix it?
Yeah, it is the warning:
[ 1.565876] BUG: using smp_processor_id() in preemptible [00000000] code: udevd/312
[ 1.566123] caller is delay_mwaitx+0x40/0xa0
and yes, I think so. I don't think we care about being in preemptible
context since we're going idle anyway and doesn't matter which cpu_tss
we touch.
Yeah, I'll use raw_cpu_ptr...
> It may pay to move it into the loop, though.
... and won't need to do that.
Thanks for the idea.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
next prev parent reply other threads:[~2016-03-09 18:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-09 11:37 [RFC PATCH] x86/delay: Do not use cpu_tss in preemptible ctxt in delay_mwaitx() Borislav Petkov
2016-03-09 17:56 ` Andy Lutomirski
2016-03-09 18:10 ` Borislav Petkov [this message]
2016-03-09 20:56 ` [PATCH] x86/delay: Avoid preemptible context checks " Borislav Petkov
2016-03-10 11:07 ` [tip:x86/urgent] " tip-bot for Borislav Petkov
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