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From: Ankur Arora <ankur.a.arora@oracle.com>
To: linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org,
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        sshegde@linux.ibm.com, boris.ostrovsky@oracle.com,
        konrad.wilk@oracle.com, Ankur Arora <ankur.a.arora@oracle.com>
Subject: [PATCH v2 05/35] thread_info: selector for TIF_NEED_RESCHED[_LAZY]
Date: Mon, 27 May 2024 17:34:51 -0700
Message-Id: <20240528003521.979836-6-ankur.a.arora@oracle.com>
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Define tif_resched() to serve as selector for the specific
need-resched flag: with tif_resched() mapping to TIF_NEED_RESCHED
or to TIF_NEED_RESCHED_LAZY.

For !CONFIG_PREEMPT_AUTO, tif_resched() always evaluates
to TIF_NEED_RESCHED, preserving existing scheduling behaviour.

Cc: Peter Ziljstra <peterz@infradead.org>
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 include/linux/thread_info.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 06e13e7acbe2..65e5beedc915 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -71,6 +71,31 @@ enum syscall_work_bit {
 #define _TIF_NEED_RESCHED_LAZY _TIF_NEED_RESCHED
 #endif
 
+typedef enum {
+	RESCHED_NOW = 0,
+	RESCHED_LAZY = 1,
+} resched_t;
+
+/*
+ * tif_resched(r) maps to TIF_NEED_RESCHED[_LAZY] with CONFIG_PREEMPT_AUTO.
+ *
+ * For !CONFIG_PREEMPT_AUTO, both tif_resched(RESCHED_NOW) and
+ * tif_resched(RESCHED_LAZY) reduce to the same value (TIF_NEED_RESCHED)
+ * leaving any scheduling behaviour unchanged.
+ */
+static __always_inline int tif_resched(resched_t rs)
+{
+	if (IS_ENABLED(CONFIG_PREEMPT_AUTO))
+		return (rs == RESCHED_NOW) ? TIF_NEED_RESCHED : TIF_NEED_RESCHED_LAZY;
+	else
+		return TIF_NEED_RESCHED;
+}
+
+static __always_inline int _tif_resched(resched_t rs)
+{
+	return 1 << tif_resched(rs);
+}
+
 #ifdef __KERNEL__
 
 #ifndef arch_set_restart_data
-- 
2.31.1