From: "Arnd Bergmann" <arnd@arndb.de>
To: "Paul E. McKenney" <paulmck@kernel.org>,
"Akira Yokosawa" <akiyks@gmail.com>
Cc: "John Paul Adrian Glaubitz" <glaubitz@physik.fu-berlin.de>,
"Ivan Kokshaysky" <ink@jurassic.park.msu.ru>,
linux-alpha@vger.kernel.org,
Linux-Arch <linux-arch@vger.kernel.org>,
linux-kernel@vger.kernel.org, "Matt Turner" <mattst88@gmail.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Ulrich Teichert" <krypton@ulrich-teichert.org>
Subject: Re: [GIT PULL] alpha: cleanups and build fixes for 6.10
Date: Mon, 13 May 2024 08:28:32 +0200 [thread overview]
Message-ID: <11bd3fe9-302c-4554-886b-f4a883f8de36@app.fastmail.com> (raw)
In-Reply-To: <ec4e905b-030c-43bb-818a-f4a0299597f7@paulmck-laptop>
On Mon, May 13, 2024, at 06:03, Paul E. McKenney wrote:
> On Mon, May 13, 2024 at 12:50:07PM +0900, Akira Yokosawa wrote:
>> On Sun, 12 May 2024 07:44:25 -0700, Paul E. McKenney wrote:
>> > On Sun, May 12, 2024 at 08:02:59AM +0200, John Paul Adrian Glaubitz wrote:
>> > So why didn't the people running current mainline on pre-EV56 Alpha
>> > systems notice? One possibility is that they are upgrading their
>> > kernels only occasionally. Another possibility is that they are seeing
>> > the failures, but are not tracing the obtuse failure modes back to the
>> > change(s) in question. Yet another possibility is that the resulting
>> > failures are very low probability, with mean times to failure that are
>> > so long that you won't notice anything on a single system.
>>
>> Another possibility is that the Jensen system was booted into uni processer
>> mode. Looking at the early boot log [1] provided by Ulrich (+CCed) back in
>> Sept. 2021, I see the following by running "grep -i cpu":
>>
>> >> > [1] https://marc.info/?l=linux-alpha&m=163265555616841&w=2
>>
>> [ 0.000000] Memory: 90256K/131072K available (8897K kernel code, 9499K rwdata, \
>> 2704K rodata, 312K init, 437K bss, 40816K reserved, 0K cma-reserved) [ 0.000000] \
>> random: get_random_u64 called from __kmem_cache_create+0x54/0x600 with crng_init=0 [ \
>> 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1 [ 0.000000]
>> ^^^^^^
>>
>> Without any concurrent atomic updates, the "broken" atomic accesses won't
>> matter, I guess.
>
> True enough!
On the other hand, you would get the same broken behavior on
any SMP machine running a kernel that has support for EV5 or
earlier enabled in a multiplatform kernel. It doesn't really
matter if it's running on hardware that supports BWX or not
as long as the compiler doesn't generate those instructions.
If I understand it correctly, simply running rcutorture on
a large alpha machine with a 'defconfig' kernel from the
past two years should trigger some bugs even if you don't
run into them that frequently on light usage, right?
Arnd
next prev parent reply other threads:[~2024-05-13 6:28 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-10 21:17 [GIT PULL] asm-generic cleanups for 6.10 Arnd Bergmann
2024-05-10 21:19 ` [GIT PULL] alpha: cleanups and build fixes " Arnd Bergmann
2024-05-10 21:40 ` John Paul Adrian Glaubitz
2024-05-10 22:28 ` Paul E. McKenney
2024-05-11 18:49 ` John Paul Adrian Glaubitz
2024-05-11 19:37 ` Paul E. McKenney
2024-05-11 20:08 ` Arnd Bergmann
2024-05-12 1:26 ` Paul E. McKenney
2024-05-12 6:02 ` John Paul Adrian Glaubitz
2024-05-12 14:44 ` Paul E. McKenney
2024-05-13 3:50 ` Akira Yokosawa
2024-05-13 4:03 ` Paul E. McKenney
2024-05-13 6:28 ` Arnd Bergmann [this message]
2024-05-13 9:26 ` John Paul Adrian Glaubitz
2024-05-13 16:52 ` Ulrich Teichert
2024-05-13 21:44 ` John Paul Adrian Glaubitz
2024-05-13 7:10 ` John Paul Adrian Glaubitz
2024-05-12 6:17 ` John Paul Adrian Glaubitz
2024-05-13 16:27 ` Linus Torvalds
2024-05-13 21:42 ` John Paul Adrian Glaubitz
2024-05-31 2:53 ` Maciej W. Rozycki
2024-05-13 17:05 ` pr-tracker-bot
2024-05-13 16:11 ` [GIT PULL] asm-generic cleanups " Linus Torvalds
2024-05-13 16:36 ` Arnd Bergmann
2024-05-20 22:35 ` pr-tracker-bot
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