linux-kernel - [RFC PATCH 11/14] csky/thread_info: Introduce TIF_NOTIFY

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Message-ID: <20240220171457.703-12-kprateek.nayak@amd.com>
Date: Tue, 20 Feb 2024 22:44:54 +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>, Guo Ren <guoren@...nel.org>, "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>, <linux-csky@...r.kernel.org>,
	<linux-pm@...r.kernel.org>
Subject: [RFC PATCH 11/14] csky/thread_info: Introduce TIF_NOTIFY_IPI flag

Add support for TIF_NOTIFY_IPI on C-SKY. 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: Guo Ren <guoren@...nel.org>
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: K Prateek Nayak <kprateek.nayak@....com>
Cc: linux-csky@...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/csky/include/asm/thread_info.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/csky/include/asm/thread_info.h b/arch/csky/include/asm/thread_info.h
index b5ed788f0c68..9bc7a037c476 100644
--- a/arch/csky/include/asm/thread_info.h
+++ b/arch/csky/include/asm/thread_info.h
@@ -61,6 +61,7 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_SYSCALL_TRACEPOINT	5       /* syscall tracepoint instrumentation */
 #define TIF_SYSCALL_AUDIT	6	/* syscall auditing */
 #define TIF_NOTIFY_SIGNAL	7	/* signal notifications exist */
+#define TIF_NOTIFY_IPI		8	/* Pending IPI on TIF_POLLLING idle CPU */
 #define TIF_POLLING_NRFLAG	16	/* poll_idle() is TIF_NEED_RESCHED */
 #define TIF_MEMDIE		18      /* is terminating due to OOM killer */
 #define TIF_RESTORE_SIGMASK	20	/* restore signal mask in do_signal() */
@@ -73,6 +74,7 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
+#define _TIF_NOTIFY_IPI		(1 << TIF_NOTIFY_IPI)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 #define _TIF_MEMDIE		(1 << TIF_MEMDIE)
-- 
2.34.1