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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>, Richard Henderson <richard.henderson@linaro.org>,
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	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>, Al Viro <viro@zeniv.linux.org.uk>,
	<linux-alpha@vger.kernel.org>, <linux-pm@vger.kernel.org>
Subject: [RFC PATCH 06/14] alpha/thread_info: Introduce TIF_NOTIFY_IPI flag
Date: Tue, 20 Feb 2024 22:44:49 +0530
Message-ID: <20240220171457.703-7-kprateek.nayak@amd.com>
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Add support for TIF_NOTIFY_IPI on Alpha. 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: Richard Henderson <richard.henderson@linaro.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.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: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-alpha@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
---
 arch/alpha/include/asm/thread_info.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/alpha/include/asm/thread_info.h b/arch/alpha/include/asm/thread_info.h
index 4a4d00b37986..8c17855c85c7 100644
--- a/arch/alpha/include/asm/thread_info.h
+++ b/arch/alpha/include/asm/thread_info.h
@@ -64,6 +64,7 @@ register unsigned long *current_stack_pointer __asm__ ("$30");
 #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
 #define TIF_SYSCALL_AUDIT	4	/* syscall audit active */
 #define TIF_NOTIFY_SIGNAL	5	/* signal notifications exist */
+#define TIF_NOTIFY_IPI		6	/* Pending IPI on TIF_POLLLING idle CPU */
 #define TIF_DIE_IF_KERNEL	9	/* dik recursion lock */
 #define TIF_MEMDIE		13	/* is terminating due to OOM killer */
 #define TIF_POLLING_NRFLAG	14	/* idle is polling for TIF_NEED_RESCHED */
@@ -74,6 +75,7 @@ register unsigned long *current_stack_pointer __asm__ ("$30");
 #define _TIF_NOTIFY_RESUME	(1<<TIF_NOTIFY_RESUME)
 #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_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
 
 /* Work to do on interrupt/exception return.  */
-- 
2.34.1