From: David Laight <David.Laight@ACULAB.COM>
To: 'Andy Lutomirski' <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
"Luck, Tony" <tony.luck@intel.com>,
"Yu, Fenghua" <fenghua.yu@intel.com>,
Ingo Molnar <mingo@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "Borislav Petkov" <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>, "Raj, Ashok" <ashok.raj@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
"Will Deacon" <will@kernel.org>
Subject: RE: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter
Date: Mon, 16 Dec 2019 17:45:22 +0000 [thread overview]
Message-ID: <053a199934844aef9745d7398494b5a0@AcuMS.aculab.com> (raw)
In-Reply-To: <CALCETrW1LDuzcnvav=MY1bUv4jQ25n30La5m5x8tXfDknfV_cQ@mail.gmail.com>
From: Andy Lutomirski
> Sent: 16 December 2019 17:23
...
> I'm talking specifically about x86 here, where, for example, "Reads
> are not reordered with other reads". So READ_ONCE *does* have
> sequencing requirements on the CPUs.
>
> Feel free to replace READ_ONCE with MOV in your head if you like :)
I got a little confused because I thought your reference to READ_ONCE()
was relevant.
Sometimes remembering all this gets hard.
The docs about the effects of LFENCE and MFENCE don't really help
(they make my brain hurt).
I'm pretty sure I've decided in the past they are almost never needed.
Usually the ordering of reads doesn't help you.
IIRC If locations 'a' and 'b' get changed from 0 to 1 it is perfectly possible
for one cpu to see a==0, b==1 and another a==1, b==0 even
though both read a then b.
(On non-alpha this may require different cpus update a and b.)
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2019-12-16 17:45 UTC|newest]
Thread overview: 145+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-21 0:53 [PATCH v10 0/6] Enable split lock detection for real time and debug Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 1/6] x86/msr-index: Add two new MSRs Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 2/6] x86/cpufeatures: Enumerate the IA32_CORE_CAPABILITIES MSR Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 3/6] x86/split_lock: Enumerate split lock detection by " Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 4/6] x86/split_lock: Enumerate split lock detection if the IA32_CORE_CAPABILITIES MSR is not supported Fenghua Yu
2019-11-21 22:07 ` Andy Lutomirski
2019-11-22 0:37 ` Fenghua Yu
2019-11-22 2:13 ` Andy Lutomirski
2019-11-22 9:46 ` Peter Zijlstra
2019-11-21 0:53 ` [PATCH v10 5/6] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-11-21 22:10 ` Andy Lutomirski
2019-11-21 23:14 ` Fenghua Yu
2019-11-21 23:12 ` Andy Lutomirski
2019-11-21 0:53 ` [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter Fenghua Yu
2019-11-21 6:04 ` Ingo Molnar
2019-11-21 13:01 ` Peter Zijlstra
2019-11-21 13:15 ` Peter Zijlstra
2019-11-21 21:51 ` Luck, Tony
2019-11-21 22:24 ` Andy Lutomirski
2019-11-21 22:29 ` Luck, Tony
2019-11-21 23:18 ` Andy Lutomirski
2019-11-21 23:53 ` Fenghua Yu
2019-11-22 1:52 ` Sean Christopherson
2019-11-22 2:21 ` Andy Lutomirski
2019-11-22 2:39 ` Xiaoyao Li
2019-11-22 2:57 ` Andy Lutomirski
2019-11-21 23:55 ` Luck, Tony
2019-11-22 0:55 ` Luck, Tony
2019-11-22 10:08 ` Peter Zijlstra
2019-11-21 16:14 ` Fenghua Yu
2019-11-21 17:14 ` Ingo Molnar
2019-11-21 17:35 ` Peter Zijlstra
2019-11-21 17:12 ` Ingo Molnar
2019-11-21 17:34 ` Luck, Tony
2019-11-22 10:51 ` Peter Zijlstra
2019-11-22 15:27 ` Peter Zijlstra
2019-11-22 17:22 ` Luck, Tony
2019-11-22 20:23 ` Peter Zijlstra
2019-11-22 18:02 ` Luck, Tony
2019-11-22 20:23 ` Peter Zijlstra
2019-11-22 20:42 ` Fenghua Yu
2019-11-22 21:25 ` Andy Lutomirski
2019-12-12 8:57 ` Peter Zijlstra
2019-12-12 18:52 ` Luck, Tony
2019-12-12 19:46 ` Luck, Tony
2019-12-12 20:01 ` Andy Lutomirski
2019-12-16 16:21 ` David Laight
2019-11-22 18:44 ` Sean Christopherson
2019-11-22 20:30 ` Peter Zijlstra
2019-11-23 0:30 ` Luck, Tony
2019-11-25 16:13 ` Sean Christopherson
2019-12-02 18:20 ` Luck, Tony
2019-12-12 8:59 ` Peter Zijlstra
2020-01-10 19:24 ` [PATCH v11] x86/split_lock: Enable split lock detection by kernel Luck, Tony
2020-01-14 5:55 ` Sean Christopherson
2020-01-15 22:27 ` Luck, Tony
2020-01-15 22:57 ` Sean Christopherson
2020-01-15 23:48 ` Luck, Tony
2020-01-22 18:55 ` [PATCH v12] " Luck, Tony
2020-01-22 19:04 ` Borislav Petkov
2020-01-22 20:03 ` Luck, Tony
2020-01-22 20:55 ` Borislav Petkov
2020-01-22 22:42 ` Arvind Sankar
2020-01-22 22:52 ` Arvind Sankar
2020-01-22 23:24 ` Luck, Tony
2020-01-23 0:45 ` Arvind Sankar
2020-01-23 1:23 ` Luck, Tony
2020-01-23 4:21 ` Arvind Sankar
2020-01-23 17:15 ` Luck, Tony
2020-01-23 3:53 ` [PATCH v13] " Luck, Tony
2020-01-23 4:45 ` Arvind Sankar
2020-01-23 23:16 ` [PATCH v14] " Luck, Tony
2020-01-24 21:36 ` Thomas Gleixner
2020-01-25 2:47 ` [PATCH v15] " Luck, Tony
2020-01-25 10:44 ` Borislav Petkov
2020-01-25 19:55 ` Luck, Tony
2020-01-25 20:12 ` Peter Zijlstra
2020-01-25 20:33 ` Borislav Petkov
2020-01-25 21:42 ` Luck, Tony
2020-01-25 22:17 ` Borislav Petkov
2020-01-25 20:29 ` Borislav Petkov
2020-01-25 13:41 ` Thomas Gleixner
2020-01-25 22:07 ` [PATCH v16] " Luck, Tony
2020-01-25 22:43 ` Mark D Rustad
2020-01-25 23:10 ` Luck, Tony
2020-01-26 17:27 ` Mark D Rustad
2020-01-26 20:05 ` [PATCH v17] " Luck, Tony
2020-01-29 12:31 ` Thomas Gleixner
2020-01-29 15:24 ` [tip: x86/cpu] " tip-bot2 for Peter Zijlstra (Intel)
2020-02-03 20:41 ` [PATCH v17] " Sean Christopherson
2020-02-06 0:49 ` [PATCH] x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR Luck, Tony
2020-02-06 1:18 ` Andy Lutomirski
2020-02-06 16:46 ` Luck, Tony
2020-02-06 19:37 ` Andy Lutomirski
2020-03-03 19:22 ` Sean Christopherson
2020-02-04 0:04 ` [PATCH v17] x86/split_lock: Enable split lock detection by kernel Sean Christopherson
2020-02-04 12:52 ` Thomas Gleixner
2020-01-26 0:34 ` [PATCH v16] " Andy Lutomirski
2020-01-26 20:01 ` Luck, Tony
2020-01-25 21:25 ` [PATCH v15] " Arvind Sankar
2020-01-25 21:50 ` Luck, Tony
2020-01-25 23:51 ` Arvind Sankar
2020-01-26 2:52 ` Luck, Tony
2020-01-27 2:05 ` Tony Luck
2020-01-27 8:04 ` Peter Zijlstra
2020-01-27 8:36 ` Peter Zijlstra
2020-01-27 17:35 ` Luck, Tony
2020-01-27 8:02 ` Peter Zijlstra
2019-12-13 0:09 ` [PATCH v11] x86/split_lock: Enable split lock detection by kernel parameter Tony Luck
2019-12-13 0:16 ` Luck, Tony
2019-11-21 17:43 ` [PATCH v10 6/6] " David Laight
2019-11-21 17:51 ` Andy Lutomirski
2019-11-21 18:53 ` Fenghua Yu
2019-11-21 19:01 ` Andy Lutomirski
2019-11-21 20:25 ` Fenghua Yu
2019-11-21 20:19 ` Peter Zijlstra
2019-11-21 19:46 ` Peter Zijlstra
2019-11-21 20:25 ` Peter Zijlstra
2019-11-21 21:22 ` Andy Lutomirski
2019-11-22 9:25 ` Peter Zijlstra
2019-11-22 17:48 ` Luck, Tony
2019-11-22 20:31 ` Peter Zijlstra
2019-11-22 21:23 ` Andy Lutomirski
2019-12-11 17:52 ` Peter Zijlstra
2019-12-11 18:12 ` Andy Lutomirski
2019-12-11 22:34 ` Peter Zijlstra
2019-12-12 19:40 ` Andy Lutomirski
2019-12-16 9:59 ` David Laight
2019-12-16 17:22 ` Andy Lutomirski
2019-12-16 17:45 ` David Laight [this message]
2019-12-16 18:06 ` Andy Lutomirski
2019-12-17 10:03 ` David Laight
2019-12-11 18:44 ` Luck, Tony
2019-12-11 22:39 ` Peter Zijlstra
2019-12-12 10:36 ` David Laight
2019-12-12 13:04 ` Peter Zijlstra
2019-12-12 16:02 ` Andy Lutomirski
2019-12-12 16:23 ` David Laight
2019-12-12 16:29 ` David Laight
2019-11-21 19:56 ` Peter Zijlstra
2019-11-21 21:01 ` Andy Lutomirski
2019-11-22 9:36 ` Peter Zijlstra
2019-11-22 9:46 ` David Laight
2019-11-22 20:32 ` Peter Zijlstra
2019-11-21 8:00 ` Peter Zijlstra
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