From: Peter Zijlstra <peterz@infradead.org>
To: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Xiong Zhou <jencce.kernel@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
Andreas Herrmann <aherrmann@suse.com>
Subject: Re: 4.5.0+ panic when setup loop device
Date: Fri, 18 Mar 2016 08:51:15 +0100 [thread overview]
Message-ID: <20160318075115.GD6344@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1458274314.3859.25.camel@gmail.com>
On Fri, Mar 18, 2016 at 05:11:54AM +0100, Mike Galbraith wrote:
> On Thu, 2016-03-17 at 10:52 +0100, Peter Zijlstra wrote:
>
> > Andreas; Borislav said to Cc you since you wrote all this.
> > The issue is that Linux assumes:
> >
> > > nr_logical_cpus = nr_cores * nr_siblings
>
> It also seems to now assume that if SMT is possible, it's enabled.
Urgh..
What I think, with my pre wakeup brain, happens is that the CPUID
topology muck still reports 2 siblings (it tends to do that).
But the BIOS only reports APIC-IDs for all your cores, so our
nr_cpu_ids is reduced, while the nr_siblings count it not.
And them *boom*.
This is the same old problem that is nearly impossible to tell if HT is
enabled or not -- complete and utter trainwreck :/
I need to go make wake-up-juice and ponder wth to do about this.
next prev parent reply other threads:[~2016-03-18 7:52 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-16 6:48 4.5.0+ panic when setup loop device Xiong Zhou
2016-03-16 15:26 ` Thomas Gleixner
2016-03-17 1:56 ` Xiong Zhou
2016-03-17 9:52 ` Peter Zijlstra
2016-03-17 9:56 ` Peter Zijlstra
2016-03-17 10:21 ` Thomas Gleixner
2016-03-17 10:26 ` Peter Zijlstra
2016-03-17 11:39 ` Thomas Gleixner
2016-03-17 11:51 ` Peter Zijlstra
2016-03-17 11:57 ` Borislav Petkov
2016-03-17 12:01 ` Thomas Gleixner
2016-03-17 16:42 ` Jens Axboe
2016-03-17 18:26 ` Jens Axboe
2016-03-17 20:20 ` Thomas Gleixner
2016-03-17 20:23 ` Jens Axboe
2016-03-17 20:30 ` Thomas Gleixner
2016-03-17 20:41 ` Jens Axboe
2016-03-18 2:31 ` Xiong Zhou
2016-03-18 4:11 ` Mike Galbraith
2016-03-18 7:51 ` Peter Zijlstra [this message]
2016-03-18 10:15 ` Peter Zijlstra
2016-03-18 12:39 ` Mike Galbraith
2016-03-18 13:32 ` Peter Zijlstra
2016-03-18 14:07 ` Mike Galbraith
2016-03-18 11:55 ` Thomas Gleixner
2016-03-18 12:39 ` Mike Galbraith
2016-03-19 9:31 ` [tip:x86/urgent] x86/topology: Use total_cpus not nr_cpu_ids for logical packages tip-bot for Thomas Gleixner
2016-03-29 8:48 ` [tip:x86/urgent] x86/topology: Fix AMD core count tip-bot for Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2016-03-18 15:03 [PATCH 0/3] x86 topology fixes Peter Zijlstra
2016-03-18 15:03 ` [PATCH 1/3] x86/topology: Fix logical pkg mapping Peter Zijlstra
2016-03-19 9:30 ` [tip:x86/urgent] x86/topology: Fix logical package mapping tip-bot for Peter Zijlstra
2016-03-18 15:03 ` [PATCH 2/3] x86/topology: Fix AMD core count Peter Zijlstra
2016-03-18 16:41 ` Borislav Petkov
2016-03-21 3:07 ` Huang Rui
2016-03-21 3:46 ` Huang Rui
2016-03-21 8:26 ` Borislav Petkov
2016-03-21 9:18 ` Huang Rui
2016-03-21 8:56 ` Thomas Gleixner
2016-03-21 8:21 ` Peter Zijlstra
2016-03-21 9:46 ` Huang Rui
2016-03-21 13:57 ` Borislav Petkov
2016-03-22 8:10 ` Sherry Hurwitz
2016-03-22 11:22 ` Borislav Petkov
2016-03-21 8:23 ` Borislav Petkov
2016-03-21 10:05 ` Huang Rui
2016-03-21 10:23 ` Borislav Petkov
2016-03-19 9:24 ` Thomas Gleixner
2016-03-19 15:56 ` Borislav Petkov
2016-03-20 10:39 ` Peter Zijlstra
2016-03-20 11:04 ` Borislav Petkov
2016-03-20 12:32 ` Peter Zijlstra
2016-03-20 12:46 ` Peter Zijlstra
2016-03-20 13:09 ` Borislav Petkov
2016-03-20 17:08 ` Peter Zijlstra
2016-03-20 18:46 ` Borislav Petkov
2016-03-29 8:49 ` [tip:x86/urgent] perf/x86/amd: Cleanup Fam10h NB event constraints tip-bot for Peter Zijlstra
2016-03-22 7:56 ` [PATCH 2/3] x86/topology: Fix AMD core count Huang Rui
2016-03-18 15:03 ` [PATCH 3/3] x86/topology: Fix Intel HT disable Peter Zijlstra
2016-03-19 9:31 ` [tip:x86/urgent] " tip-bot for Peter Zijlstra
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