linux-kernel - [RFC PATCH 10/14] sparc/thread_info: Introduce TIF_NOTIFY

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Date: Tue, 20 Feb 2024 22:44:53 +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>, "David S. Miller" <davem@...emloft.net>, "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>, <sparclinux@...r.kernel.org>,
	<linux-pm@...r.kernel.org>
Subject: [RFC PATCH 10/14] sparc/thread_info: Introduce TIF_NOTIFY_IPI flag

Add support for TIF_NOTIFY_IPI on SPARC. 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: "David S. Miller" <davem@...emloft.net>
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: sparclinux@...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/sparc/include/asm/thread_info_32.h | 2 ++
 arch/sparc/include/asm/thread_info_64.h | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/arch/sparc/include/asm/thread_info_32.h b/arch/sparc/include/asm/thread_info_32.h
index 45b4955b253f..f538ede526d1 100644
--- a/arch/sparc/include/asm/thread_info_32.h
+++ b/arch/sparc/include/asm/thread_info_32.h
@@ -105,6 +105,7 @@ register struct thread_info *current_thread_info_reg asm("g6");
 #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
 #define TIF_RESTORE_SIGMASK	4	/* restore signal mask in do_signal() */
 #define TIF_NOTIFY_SIGNAL	5	/* signal notifications exist */
+#define TIF_NOTIFY_IPI		6	/* Pending IPI on TIF_POLLLING idle CPU */
 #define TIF_USEDFPU		8	/* FPU was used by this task
 					 * this quantum (SMP) */
 #define TIF_POLLING_NRFLAG	9	/* true if poll_idle() is polling
@@ -117,6 +118,7 @@ register struct thread_info *current_thread_info_reg asm("g6");
 #define _TIF_SIGPENDING		(1<<TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1<<TIF_NEED_RESCHED)
 #define _TIF_NOTIFY_SIGNAL	(1<<TIF_NOTIFY_SIGNAL)
+#define _TIF_NOTIFY_IPI		(1<<TIF_NOTIFY_IPI)
 #define _TIF_USEDFPU		(1<<TIF_USEDFPU)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
 
diff --git a/arch/sparc/include/asm/thread_info_64.h b/arch/sparc/include/asm/thread_info_64.h
index 1a44372e2bc0..3558101ccdd1 100644
--- a/arch/sparc/include/asm/thread_info_64.h
+++ b/arch/sparc/include/asm/thread_info_64.h
@@ -194,6 +194,7 @@ extern struct thread_info *current_thread_info(void);
 #define TIF_MCDPER		12	/* Precise MCD exception */
 #define TIF_MEMDIE		13	/* is terminating due to OOM killer */
 #define TIF_POLLING_NRFLAG	14
+#define TIF_NOTIFY_IPI		15	/* Pending IPI on TIF_POLLLING idle CPU */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME	(1<<TIF_NOTIFY_RESUME)
@@ -208,6 +209,7 @@ extern struct thread_info *current_thread_info(void);
 #define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SYSCALL_TRACEPOINT	(1<<TIF_SYSCALL_TRACEPOINT)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
+#define _TIF_NOTIFY_IPI		(1<<TIF_NOTIFY_IPI)
 
 #define _TIF_USER_WORK_MASK	((0xff << TI_FLAG_WSAVED_SHIFT) | \
 				 _TIF_DO_NOTIFY_RESUME_MASK | \
-- 
2.34.1