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From: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org>
To: Vipin Sharma <vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	rdunlap-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org,
	thomas.lendacky-5C7GfCeVMHo@public.gmane.org,
	brijesh.singh-5C7GfCeVMHo@public.gmane.org,
	jon.grimm-5C7GfCeVMHo@public.gmane.org,
	eric.vantassell-5C7GfCeVMHo@public.gmane.org,
	pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
	hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org,
	frankja-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org,
	borntraeger-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org,
	corbet-T1hC0tSOHrs@public.gmane.org,
	seanjc-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	vkuznets-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
	wanpengli-1Nz4purKYjRBDgjK7y7TUQ@public.gmane.org,
	jmattson-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
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	tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org,
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	bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org,
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	gingell-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	dionnaglaze-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
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	linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [Patch v3 1/2] cgroup: sev: Add misc cgroup controller
Date: Mon, 15 Mar 2021 19:34:15 +0100	[thread overview]
Message-ID: <YE+op0MZKG41EALi@blackbook> (raw)
In-Reply-To: <YEu74hkEPEyvxC85-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

[-- Attachment #1: Type: text/plain, Size: 840 bytes --]

On Fri, Mar 12, 2021 at 11:07:14AM -0800, Vipin Sharma <vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> wrote:
> We should be fine without atomic64_t because we are using unsigned
> long and not 64 bit explicitly. This will work on both 32 and 64 bit
> machines.
I see.

> But I will add READ_ONCE and WRITE_ONCE because of potential chances of
> load tearing and store tearing.
> 
> Do you agree?
Yes.

> This was only here to avoid multiple reads of capacity and making sure
> if condition and seq_print will see the same value.
Aha.

> Also, I was not aware of load and store tearing of properly aligned
> and machine word size variables. I will add READ_ONCE and WRITE_ONCE
> at other places.
Yeah, although it's theoretical, I think it also serves well to annotate
such unsychronized accesses.

Thanks,
Michal

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WARNING: multiple messages have this Message-ID (diff)
From: "Michal Koutný" <mkoutny@suse.com>
To: Vipin Sharma <vipinsh@google.com>
Cc: tj@kernel.org, rdunlap@infradead.org, thomas.lendacky@amd.com,
	brijesh.singh@amd.com, jon.grimm@amd.com,
	eric.vantassell@amd.com, pbonzini@redhat.com, hannes@cmpxchg.org,
	frankja@linux.ibm.com, borntraeger@de.ibm.com, corbet@lwn.net,
	seanjc@google.com, vkuznets@redhat.com, wanpengli@tencent.com,
	jmattson@google.com, joro@8bytes.org, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
	gingell@google.com, rientjes@google.com, dionnaglaze@google.com,
	kvm@vger.kernel.org, x86@kernel.org, cgroups@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [Patch v3 1/2] cgroup: sev: Add misc cgroup controller
Date: Mon, 15 Mar 2021 19:34:15 +0100	[thread overview]
Message-ID: <YE+op0MZKG41EALi@blackbook> (raw)
In-Reply-To: <YEu74hkEPEyvxC85@google.com>

[-- Attachment #1: Type: text/plain, Size: 811 bytes --]

On Fri, Mar 12, 2021 at 11:07:14AM -0800, Vipin Sharma <vipinsh@google.com> wrote:
> We should be fine without atomic64_t because we are using unsigned
> long and not 64 bit explicitly. This will work on both 32 and 64 bit
> machines.
I see.

> But I will add READ_ONCE and WRITE_ONCE because of potential chances of
> load tearing and store tearing.
> 
> Do you agree?
Yes.

> This was only here to avoid multiple reads of capacity and making sure
> if condition and seq_print will see the same value.
Aha.

> Also, I was not aware of load and store tearing of properly aligned
> and machine word size variables. I will add READ_ONCE and WRITE_ONCE
> at other places.
Yeah, although it's theoretical, I think it also serves well to annotate
such unsychronized accesses.

Thanks,
Michal

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

  parent reply	other threads:[~2021-03-15 18:34 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-04 23:19 [Patch v3 0/2] cgroup: New misc cgroup controller Vipin Sharma
2021-03-04 23:19 ` [Patch v3 1/2] cgroup: sev: Add " Vipin Sharma
     [not found]   ` <20210304231946.2766648-2-vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2021-03-11 18:59     ` Michal Koutný
2021-03-11 18:59       ` Michal Koutný
2021-03-12 19:07       ` Vipin Sharma
     [not found]         ` <YEu74hkEPEyvxC85-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2021-03-15 18:34           ` Michal Koutný [this message]
2021-03-15 18:34             ` Michal Koutný
2021-03-12 19:48       ` Vipin Sharma
2021-03-12 20:51         ` Sean Christopherson
     [not found]           ` <YEvUTatAjIoP7dPD-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2021-03-12 21:18             ` Tom Lendacky
2021-03-12 21:18               ` Tom Lendacky
2021-03-19 21:28     ` Jacob Pan
2021-03-19 21:28       ` Jacob Pan
2021-03-22 18:54       ` Vipin Sharma
     [not found]         ` <YFjn7wv/iMO4Isgz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2021-03-24 16:17           ` Jacob Pan
2021-03-24 16:17             ` Jacob Pan
2021-03-24 22:09             ` Vipin Sharma
     [not found] ` <20210304231946.2766648-1-vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2021-03-04 23:19   ` [Patch v3 2/2] cgroup: sev: Miscellaneous cgroup documentation Vipin Sharma
2021-03-04 23:19     ` Vipin Sharma
2021-03-07 12:48 ` [Patch v3 0/2] cgroup: New misc cgroup controller Tejun Heo
2021-03-11 18:58   ` Michal Koutný
2021-03-11 19:39     ` Tejun Heo
2021-03-11 19:39       ` Tejun Heo
2021-03-12 17:49     ` Vipin Sharma
2021-03-12 17:49       ` Vipin Sharma
     [not found]       ` <YEupplaAWU1i0G6B-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2021-03-15 19:10         ` Michal Koutný
2021-03-15 19:10           ` Michal Koutný
2021-03-22 18:24           ` Vipin Sharma

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