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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sBzAu-00000008nTY-1JSR; Tue, 28 May 2024 15:55:44 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id E613D30058E; Tue, 28 May 2024 17:55:43 +0200 (CEST) Date: Tue, 28 May 2024 17:55:43 +0200 From: Peter Zijlstra To: Ankur Arora Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org, paulmck@kernel.org, rostedt@goodmis.org, mark.rutland@arm.com, juri.lelli@redhat.com, joel@joelfernandes.org, raghavendra.kt@amd.com, sshegde@linux.ibm.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: Re: [PATCH v2 05/35] thread_info: selector for TIF_NEED_RESCHED[_LAZY] Message-ID: <20240528155543.GA26599@noisy.programming.kicks-ass.net> References: <20240528003521.979836-1-ankur.a.arora@oracle.com> <20240528003521.979836-6-ankur.a.arora@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240528003521.979836-6-ankur.a.arora@oracle.com> On Mon, May 27, 2024 at 05:34:51PM -0700, Ankur Arora wrote: > Define tif_resched() to serve as selector for the specific > need-resched flag: with tif_resched() mapping to TIF_NEED_RESCHED > or to TIF_NEED_RESCHED_LAZY. > > For !CONFIG_PREEMPT_AUTO, tif_resched() always evaluates > to TIF_NEED_RESCHED, preserving existing scheduling behaviour. > > Cc: Peter Ziljstra > Originally-by: Thomas Gleixner > Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/ > Signed-off-by: Ankur Arora > --- > include/linux/thread_info.h | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h > index 06e13e7acbe2..65e5beedc915 100644 > --- a/include/linux/thread_info.h > +++ b/include/linux/thread_info.h > @@ -71,6 +71,31 @@ enum syscall_work_bit { > #define _TIF_NEED_RESCHED_LAZY _TIF_NEED_RESCHED > #endif > > +typedef enum { > + RESCHED_NOW = 0, > + RESCHED_LAZY = 1, > +} resched_t; > + > +/* > + * tif_resched(r) maps to TIF_NEED_RESCHED[_LAZY] with CONFIG_PREEMPT_AUTO. > + * > + * For !CONFIG_PREEMPT_AUTO, both tif_resched(RESCHED_NOW) and > + * tif_resched(RESCHED_LAZY) reduce to the same value (TIF_NEED_RESCHED) > + * leaving any scheduling behaviour unchanged. > + */ > +static __always_inline int tif_resched(resched_t rs) > +{ > + if (IS_ENABLED(CONFIG_PREEMPT_AUTO)) > + return (rs == RESCHED_NOW) ? TIF_NEED_RESCHED : TIF_NEED_RESCHED_LAZY; > + else > + return TIF_NEED_RESCHED; > +} Perhaps: if (IS_ENABLED(CONFIG_PREEMPT_AUTO) && rs == RESCHED_LAZY) return TIF_NEED_RESCHED_LAZY; return TIF_NEED_RESCHED; hmm? > + > +static __always_inline int _tif_resched(resched_t rs) > +{ > + return 1 << tif_resched(rs); > +} > + > #ifdef __KERNEL__ > > #ifndef arch_set_restart_data > -- > 2.31.1 >