From: Prarit Bhargava <prarit@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Borislav Petkov <bp@suse.de>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Len Brown <len.brown@intel.com>,
Andi Kleen <ak@linux.intel.com>, Jiri Olsa <jolsa@redhat.com>,
Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event
Date: Wed, 28 Sep 2016 06:06:45 -0400 [thread overview]
Message-ID: <57EB9635.8060103@redhat.com> (raw)
In-Reply-To: <20160928064823.GR2794@worktop>
On 09/28/2016 02:48 AM, Peter Zijlstra wrote:
> On Tue, Sep 27, 2016 at 11:26:14AM -0400, Prarit Bhargava wrote:
>> I see now that the issue is not understanding the difference between physical
>> and soft thread removal. I will write that up and get back to everyone.
>
> You don't seem to understand that from the kernels POV there is no such
> distinction.
>
And I'm saying you're wrong. Unlike PCI, CPU sysfs unplug does not completely
remove the device from the kernel's knowledge. If that were the case then
/sys/devices/system/cpu/cpuX/online (and other files left after the unplug)
wouldn't exist.
If you do a physical removal (signaled via ACPI or interrupt) the entire device
is removed from the kernel's POV.
Yes, the sysfs removal is a subset of the physical removal. But the end result
is very different.
> There is only one unplug operation that caters to both cases. Therefore
> unplug needs to assume the most stringent (ie. physical) for things to
> work right.
See last comment above.
P.
next prev parent reply other threads:[~2016-09-28 10:06 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 11:39 [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event Prarit Bhargava
2016-09-21 11:39 ` [PATCH 1/2 v3] drivers/base: Combine topology.c and cpu.c Prarit Bhargava
2016-09-21 11:39 ` [PATCH 2/2 v3] cpu hotplug: add CONFIG_PERMANENT_CPU_TOPOLOGY Prarit Bhargava
2016-09-21 13:04 ` [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event Borislav Petkov
2016-09-21 13:32 ` Prarit Bhargava
2016-09-21 14:01 ` Borislav Petkov
2016-09-22 11:59 ` Prarit Bhargava
2016-09-22 12:10 ` Borislav Petkov
2016-09-26 11:45 ` Prarit Bhargava
2016-09-26 11:57 ` Borislav Petkov
2016-09-27 11:45 ` Prarit Bhargava
2016-09-27 13:49 ` Greg Kroah-Hartman
2016-09-27 15:26 ` Prarit Bhargava
2016-09-28 5:05 ` Borislav Petkov
2016-09-28 6:48 ` Peter Zijlstra
2016-09-28 10:06 ` Prarit Bhargava [this message]
2016-09-28 5:02 ` Borislav Petkov
2016-09-26 11:59 ` Peter Zijlstra
2016-09-27 11:47 ` Prarit Bhargava
2016-09-27 11:57 ` Peter Zijlstra
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