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[2003:f6:af14:3c00:9650:2efe:173b:4a64]) by smtp.gmail.com with ESMTPSA id i25-20020a170906115900b00982855d27c3sm417967eja.173.2023.06.14.07.30.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Jun 2023 07:30:01 -0700 (PDT) Message-ID: <23fb8ad7-beb0-ae1c-fa5a-a682a57f79b0@grsecurity.net> Date: Wed, 14 Jun 2023 16:30:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: Observing RCU stalls in kernel 5.4/5.10/5.15/6.1 stable trees Content-Language: en-US, de-DE To: Luiz Capitulino , Sven-Haegar Koch Cc: Sebastian Andrzej Siewior , "gregkh@linuxfoundation.org" , "Bhatnagar, Rishabh" , "linux-kernel@vger.kernel.org" , "tglx@linutronix.de" , "sashal@kernel.org" , abuehaze@amazon.com, "stable@vger.kernel.org" References: <12c6f9a3-d087-b824-0d05-0d18c9bc1bf3@amazon.com> <2023061428-compacter-economic-b648@gregkh> <20230614092045.tNY8USjq@linutronix.de> <4c4178a1-1050-ced4-e6fb-f95c3bdefc98@amazon.com> <2a3fa097-8ba0-5b0e-f506-779fee5b8fef@sdinet.de> From: Mathias Krause In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14.06.23 15:57, Luiz Capitulino wrote: > On 2023-06-14 09:45, Sven-Haegar Koch wrote: >> May be this, talking about the same commit as cause as this thread: >> >> Subject: Re: [PATCH] timekeeping: Align tick_sched_timer() with the HZ >> tick. -- regression report >> https://lore.kernel.org/lkml/5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecurity.net/ > > Thank you, Sven. > > Sebastian, except for the detailed analysis which we haven't done yet, the > issue described by Mathias matches 100% what we're observing. Also, we do > observe this on bare-metal instances which could mean that the initial > reports are against VMs because those are rebooted more often (our quick > reproducer boots hundreds of instances in AWS and only 1 or 2 reproduces > this). Yeah, we're doing VM based testing more often than bare metal -- less so on a AWS scale. That's why we observed it first in VMs. But that wasn't meant to exclude bare metal, not at all. It's just, that we haven't tried hard enough yet and testing VMs is so much more pleasant when it comes to debugging boot issues ;) Thanks, Mathias > IMHO, I'd suggest we revert this for now from Linus tree and stable trees. > We can help testing for the fix maybe for the next merge window. > > - Luiz >