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b=Du93MwM6A4yzmEjYWUhTBfW6L1iVoOF+OQp09nBdR2VTndmQSvCBzDyospLfbtp4y vSPp9wFK62CkMelOCD3JSgNe7WUkZ3PfHVdpQC202YcH8eBeUkcY/M/xrkspVUVWPr crK5r9LDiNrQu9ad/bc4MrftMSia3MjEheWFPLqE8lN/FcX8pUEWxRIFpJMPZrMKWy omLLup/+VZTMVK8Xpgpoxw7rIw+iOFYE9Vy3v216jXbOiceppqb5WIAzo9pUF00gMa 8cxzMWdY7ZPhZH6ufq6HV0CIoyVACGkenBG72gBiLPsZxe8u/kMSU/BXp96WfzJl0V R+iq8dC9P7B0w== Date: Thu, 9 Nov 2023 09:26:37 -0800 From: Josh Poimboeuf To: Steven Rostedt Cc: Ankur Arora , linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, paulmck@kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, mingo@kernel.org, bristot@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com, mattst88@gmail.com, krypton@ulrich-teichert.org, David.Laight@ACULAB.COM, richard@nod.at, mjguzik@gmail.com, Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , live-patching@vger.kernel.org Subject: Re: [RFC PATCH 07/86] Revert "livepatch,sched: Add livepatch task switching to cond_resched()" Message-ID: <20231109172637.ayue3jexgdxd53tu@treble> References: <20231107215742.363031-1-ankur.a.arora@oracle.com> <20231107215742.363031-8-ankur.a.arora@oracle.com> <20231107181609.7e9e9dcc@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231107181609.7e9e9dcc@gandalf.local.home> X-Rspamd-Queue-Id: 1DEA04000A X-Rspam-User: X-Stat-Signature: 76kpzfysmxrxhde8hnzkg3dzjjmtkepa X-Rspamd-Server: rspam03 X-HE-Tag: 1699550804-954855 X-HE-Meta: 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 UZzhzRb1 /Q3sG27JXWAAGNlRXIJ3jwS1XaqM/qKW/vS3PQilYGGwiQoUeGQEgQZDBrVktxtoEnrjsEb+GPc97zkcF9TLApDr30FNsNCv6G09vNr/+I6nACgQnGmZbCHGRIPLEEQz4W5x5xxzXBCKKxbrB1mTLKdf835+orqT4Lu1N0W6inJqIdj3jLpGc1a4G1k/6ostF5fWcKLU3Z+h7H4QPq/HGExAjHUJbTTjflV0q7SxLM7ej0yyV9OpVKBxgc82G3ZxXuptD X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Nov 07, 2023 at 06:16:09PM -0500, Steven Rostedt wrote: > On Tue, 7 Nov 2023 13:56:53 -0800 > Ankur Arora wrote: > > > This reverts commit e3ff7c609f39671d1aaff4fb4a8594e14f3e03f8. > > > > Note that removing this commit reintroduces "live patches failing to > > complete within a reasonable amount of time due to CPU-bound kthreads." > > > > Unfortunately this fix depends quite critically on PREEMPT_DYNAMIC and > > existence of cond_resched() so this will need an alternate fix. We definitely don't want to introduce a regression, something will need to be figured out before removing cond_resched(). We could hook into preempt_schedule_irq(), but that wouldn't work for non-ORC. Another option would be to hook into schedule(). Then livepatch could set TIF_NEED_RESCHED on remaining unpatched tasks. But again if they go through the preemption path then we have the same problem for non-ORC. Worst case we'll need to sprinkle cond_livepatch() everywhere :-/ -- Josh