Received-SPF: pass (google.com: domain of linux-kernel+bounces-215637-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Date: Sat, 15 Jun 2024 03:42:56 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>, linux-kernel@vger.kernel.org,
	"Gautham R. Shenoy" <gautham.shenoy@amd.com>,
	Richard Henderson <richard.henderson@linaro.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	Matt Turner <mattst88@gmail.com>,
	Russell King <linux@armlinux.org.uk>, Guo Ren <guoren@kernel.org>,
	Michal Simek <monstr@monstr.eu>, Dinh Nguyen <dinguyen@kernel.org>,
	Jonas Bonn <jonas@southpole.se>,
	Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	Stafford Horne <shorne@gmail.com>,
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
	Helge Deller <deller@gmx.de>, Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	"David S. Miller" <davem@davemloft.net>,
	Andreas Larsson <andreas@gaisler.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Andrew Donnellan <ajd@linux.ibm.com>,
	Benjamin Gray <bgray@linux.ibm.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Xin Li <xin3.li@intel.com>, Kees Cook <keescook@chromium.org>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Tony Battersby <tonyb@cybernetics.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Brian Gerst <brgerst@gmail.com>, Leonardo Bras <leobras@redhat.com>,
	Imran Khan <imran.f.khan@oracle.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Rik van Riel <riel@surriel.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	David Vernet <void@manifault.com>,
	Julia Lawall <julia.lawall@inria.fr>, linux-alpha@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org,
	linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org,
	sparclinux@vger.kernel.org, linux-pm@vger.kernel.org,
	x86@kernel.org
Subject: Re: [PATCH v2 00/14] Introducing TIF_NOTIFY_IPI flag
Message-ID: <20240615014256.GQ8774@noisy.programming.kicks-ass.net>
References: <20240613181613.4329-1-kprateek.nayak@amd.com>
 <20240614092801.GL8774@noisy.programming.kicks-ass.net>
 <CAKfTPtBTxhbmh=605TJ9sRw-nFu6w-KY7QpAxRUh5AjhQWa2ig@mail.gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAKfTPtBTxhbmh=605TJ9sRw-nFu6w-KY7QpAxRUh5AjhQWa2ig@mail.gmail.com>

On Fri, Jun 14, 2024 at 12:48:37PM +0200, Vincent Guittot wrote:

> The main problem is that need_resched becomes somewhat meaningless
> because it doesn't  only mean "I need to resched a task" and we have
> to add more tests around even for those not using polling

The converse problem is that you're adding a bunch of atomic ops that
might be avoided.

It might now need to set both the RESCHED and IPI flags -- and clear
them again.