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([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id z8-20020a170903018800b00177c488fea5sm11736743plg.12.2022.10.12.22.20.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Oct 2022 22:20:04 -0700 (PDT) Sender: Guenter Roeck Message-ID: Date: Wed, 12 Oct 2022 22:20:01 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Content-Language: en-US To: Nicholas Piggin , Michael Ellerman Cc: "Jason A. Donenfeld" , Linus Torvalds , ajd@linux.ibm.com, aneesh.kumar@linux.ibm.com, atrajeev@linux.vnet.ibm.com, christophe.leroy@csgroup.eu, cuigaosheng1@huawei.com, david@redhat.com, farosas@linux.ibm.com, geoff@infradead.org, gustavoars@kernel.org, haren@linux.ibm.com, hbathini@linux.ibm.com, joel@jms.id.au, lihuafei1@huawei.com, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, lukas.bulwahn@gmail.com, mikey@neuling.org, nathan@kernel.org, nathanl@linux.ibm.com, nicholas@linux.ibm.com, pali@kernel.org, paul@paul-moore.com, rmclure@linux.ibm.com, ruscur@russell.cc, windhl@126.com, wsa+renesas@sang-engineering.com, ye.xingchen@zte.com.cn, yuanjilin@cdjrlc.com, zhengyongjun3@huawei.com References: <87edvhntv0.fsf@mpe.ellerman.id.au> <20221012141827.GA2405914@roeck-us.net> <20221012164452.GA2990467@roeck-us.net> <20221012221615.GA364143@roeck-us.net> <87bkqgmvxl.fsf@mpe.ellerman.id.au> <20221013002148.GA535574@roeck-us.net> From: Guenter Roeck Subject: Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/12/22 22:03, Nicholas Piggin wrote: > On Thu Oct 13, 2022 at 10:21 AM AEST, Guenter Roeck wrote: >> On Thu, Oct 13, 2022 at 11:03:34AM +1100, Michael Ellerman wrote: >>> Guenter Roeck writes: >>>> On Wed, Oct 12, 2022 at 11:20:38AM -0600, Jason A. Donenfeld wrote: >>>>> >>>>> I've also managed to not hit this bug a few times. When it triggers, >>>>> after "kprobes: kprobe jump-optimization is enabled. All kprobes are >>>>> optimized if possible.", there's a long hang - tens seconds before it >>>>> continues. When it doesn't trigger, there's no hang at that point in the >>>>> boot process. >>>>> >>>> >>>> I managed to bisect the problem. See below for results. Reverting the >>>> offending patch fixes the problem for me. >>> >>> Thanks. >>> >>> This is probably down to me/us not testing with PREEMPT enabled enough. >>> >> Not sure. My configuration has >> >> CONFIG_PREEMPT_NONE=y >> # CONFIG_PREEMPT_VOLUNTARY is not set >> # CONFIG_PREEMPT is not set > > Thanks very much for helping with this. The config snippet you posted here > https://lists.ozlabs.org/pipermail/linuxppc-dev/2022-October/249758.html > has CONFIG_PREEMPT=y. How do you turn that into a .config, olddefconfig? > > I can't reproduce this so far using your config and qemu command line, > but the patch you've bisected it to definitely could cause this. I'll > keep trying... > Uuh, sorry, I think I got confused with running multiple bisects on the same branch, and took the above from a different bisect run. You are correct, PREEMPT is enabled in the configuration. Timing is definitely involved; I see the problem more often on a loaded system. To bisect it, I had to repeat the test for each bisect step several times (I set the limit to 20 retries; that gave me reliable results). Guenter