[RFC PATCH 08/14] powerpc/thread_info: Introduce TIF_NOTIFY_IPI flag

From: K Prateek Nayak <kprateek.nayak@amd.com>
To: <linux-kernel@vger.kernel.org>
Cc: "Gautham R. Shenoy" <gautham.shenoy@amd.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Aneesh Kumar K.V <aneesh.kumar@kernel.org>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	"Daniel Lezcano" <daniel.lezcano@linaro.org>,
	Ingo Molnar <mingo@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	"Vincent Guittot" <vincent.guittot@linaro.org>,
	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>,
	Nicholas Miehlbradt <nicholas@linux.ibm.com>,
	<linuxppc-dev@lists.ozlabs.org>, <linux-pm@vger.kernel.org>
Subject: [RFC PATCH 08/14] powerpc/thread_info: Introduce TIF_NOTIFY_IPI flag
Date: Tue, 20 Feb 2024 22:44:51 +0530	[thread overview]
Message-ID: <20240220171457.703-9-kprateek.nayak@amd.com> (raw)
In-Reply-To: <20240220171457.703-1-kprateek.nayak@amd.com>

Add support for TIF_NOTIFY_IPI on PowerPC. With TIF_NOTIFY_IPI, a sender
sending an IPI to an idle CPU in TIF_POLLING mode will set the
TIF_NOTIFY_IPI flag in the target's idle tasks's thread_info to pull the
CPU out of idle, as opposed to setting TIF_NEED_RESCHED previously. This
avoids spurious calls to schedule_idle() in cases where an IPI does not
necessarily wake up a task on the idle CPU.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Andrew Donnellan <ajd@linux.ibm.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Nicholas Miehlbradt <nicholas@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
---
 arch/powerpc/include/asm/thread_info.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index bf5dde1a4114..b48db55192e0 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -103,6 +103,7 @@ void arch_setup_new_exec(void);
 #define TIF_PATCH_PENDING	6	/* pending live patching update */
 #define TIF_SYSCALL_AUDIT	7	/* syscall auditing active */
 #define TIF_SINGLESTEP		8	/* singlestepping active */
+#define TIF_NOTIFY_IPI		9	/* Pending IPI on TIF_POLLLING idle CPU */
 #define TIF_SECCOMP		10	/* secure computing */
 #define TIF_RESTOREALL		11	/* Restore all regs (implies NOERROR) */
 #define TIF_NOERROR		12	/* Force successful syscall return */
@@ -129,6 +130,7 @@ void arch_setup_new_exec(void);
 #define _TIF_PATCH_PENDING	(1<<TIF_PATCH_PENDING)
 #define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SINGLESTEP		(1<<TIF_SINGLESTEP)
+#define _TIF_NOTIFY_IPI		(1<<TIF_NOTIFY_IPI)
 #define _TIF_SECCOMP		(1<<TIF_SECCOMP)
 #define _TIF_RESTOREALL		(1<<TIF_RESTOREALL)
 #define _TIF_NOERROR		(1<<TIF_NOERROR)
-- 
2.34.1

