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McKenney" To: Ankur Arora Cc: Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, peterz@infradead.org, torvalds@linux-foundation.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, Simon Horman , Julian Anastasov , Alexei Starovoitov , Daniel Borkmann Subject: Re: [RFC PATCH 47/86] rcu: select PREEMPT_RCU if PREEMPT Message-ID: <106ab2d8-f63b-4c52-a93f-fc499d43fc13@paulmck-laptop> Reply-To: paulmck@kernel.org References: <87wmu2ywrk.ffs@tglx> <20231205100114.0bd3c4a2@gandalf.local.home> <1375e409-2593-45e1-b27e-3699c17c47dd@paulmck-laptop> <87il5cpfn1.fsf@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87il5cpfn1.fsf@oracle.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 86CE71C0011 X-Stat-Signature: ygzz45xfg4p36zcpihd9hzpua9krdoci X-Rspam-User: X-HE-Tag: 1701835672-660501 X-HE-Meta: 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 LuMYQhoE 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 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, Dec 05, 2023 at 12:18:26PM -0800, Ankur Arora wrote: > > Paul E. McKenney writes: > > > On Tue, Dec 05, 2023 at 10:01:14AM -0500, Steven Rostedt wrote: > >> On Mon, 4 Dec 2023 17:01:21 -0800 > >> "Paul E. McKenney" wrote: > >> > >> > On Tue, Nov 28, 2023 at 11:53:19AM +0100, Thomas Gleixner wrote: > >> > > Paul! > >> > > > >> > > On Tue, Nov 21 2023 at 07:19, Paul E. McKenney wrote: > >> > > > On Tue, Nov 21, 2023 at 10:00:59AM -0500, Steven Rostedt wrote: > ... > >> > > 3) Looking at the initial problem Ankur was trying to solve there is > >> > > absolutely no acceptable solution to solve that unless you think > >> > > that the semantically invers 'allow_preempt()/disallow_preempt()' > >> > > is anywhere near acceptable. > >> > > >> > I am not arguing for allow_preempt()/disallow_preempt(), so for that > >> > argument, you need to find someone else to argue with. ;-) > >> > >> Anyway, there's still a long path before cond_resched() can be removed. It > >> was a mistake by Ankur to add those removals this early (and he has > >> acknowledged that mistake). > > > > OK, that I can live with. But that seems to be a bit different of a > > take than that of some earlier emails in this thread. ;-) > > Heh I think it's just that this thread goes to (far) too many places :). > > As Steven says, the initial series touching everything all together > was a mistake. V1 adds the new preemption model alongside the existing > ones locally defines cond_resched() as nop. > > That'll allow us to experiment and figure out where there are latency > gaps. Sounds very good! Again, I am very supportive of the overall direction. Devils and details and all that. ;-) Thanx, Paul