linux-kernel - [RFC PATCH 09/14] sh/thread_info: Introduce TIF_NOTIFY

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Date: Tue, 20 Feb 2024 22:44:52 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: <linux-kernel@...r.kernel.org>
CC: "Gautham R. Shenoy" <gautham.shenoy@....com>, K Prateek Nayak
	<kprateek.nayak@....com>, Yoshinori Sato <ysato@...rs.sourceforge.jp>, "Rich
 Felker" <dalias@...c.org>, John Paul Adrian Glaubitz
	<glaubitz@...sik.fu-berlin.de>, "Rafael J. Wysocki" <rafael@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann
	<dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall
	<bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, "Daniel Bristot de
 Oliveira" <bristot@...hat.com>, Valentin Schneider <vschneid@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, Arnd Bergmann <arnd@...db.de>,
	<linux-sh@...r.kernel.org>, <linux-pm@...r.kernel.org>
Subject: [RFC PATCH 09/14] sh/thread_info: Introduce TIF_NOTIFY_IPI flag

Add support for TIF_NOTIFY_IPI on SuperH. 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: Yoshinori Sato <ysato@...rs.sourceforge.jp>
Cc: Rich Felker <dalias@...c.org>
Cc: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: K Prateek Nayak <kprateek.nayak@....com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: linux-sh@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-pm@...r.kernel.org
Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
---
 arch/sh/include/asm/thread_info.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/sh/include/asm/thread_info.h b/arch/sh/include/asm/thread_info.h
index 9f19a682d315..8cd9d2a5361b 100644
--- a/arch/sh/include/asm/thread_info.h
+++ b/arch/sh/include/asm/thread_info.h
@@ -106,6 +106,7 @@ extern void init_thread_xstate(void);
 #define TIF_SECCOMP		6	/* secure computing */
 #define TIF_NOTIFY_RESUME	7	/* callback before returning to user */
 #define TIF_SYSCALL_TRACEPOINT	8	/* for ftrace syscall instrumentation */
+#define TIF_NOTIFY_IPI		9	/* Pending IPI on TIF_POLLLING idle CPU */
 #define TIF_POLLING_NRFLAG	17	/* true if poll_idle() is polling TIF_NEED_RESCHED */
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 
@@ -118,6 +119,7 @@ extern void init_thread_xstate(void);
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
+#define _TIF_NOTIFY_IPI		(1 << TIF_NOTIFY_IPI)
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 
 /* work to do in syscall trace */
-- 
2.34.1