linux-kernel - [PATCH 04/16] preempt: Cleanup PREEMPT

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Message-Id: <20201029165019.14218-4-urezki@gmail.com>
Date:   Thu, 29 Oct 2020 17:50:07 +0100
From:   "Uladzislau Rezki (Sony)" <urezki@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Joel Fernandes <joel@...lfernandes.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Uladzislau Rezki <urezki@...il.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Ingo Molnar <mingo@...nel.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>
Subject: [PATCH 04/16] preempt: Cleanup PREEMPT_COUNT leftovers

From: Thomas Gleixner <tglx@...utronix.de>

CONFIG_PREEMPT_COUNT is now unconditionally enabled and will be
removed. Cleanup the leftovers before doing so.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
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>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 include/linux/preempt.h | 37 ++++---------------------------------
 1 file changed, 4 insertions(+), 33 deletions(-)

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 7d9c1c0e149c..513769b1edf8 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -56,8 +56,7 @@
 #define PREEMPT_DISABLED	(PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)
 
 /*
- * Disable preemption until the scheduler is running -- use an unconditional
- * value so that it also works on !PREEMPT_COUNT kernels.
+ * Disable preemption until the scheduler is running.
  *
  * Reset by start_kernel()->sched_init()->init_idle()->init_idle_preempt_count().
  */
@@ -69,7 +68,6 @@
  *
  *    preempt_count() == 2*PREEMPT_DISABLE_OFFSET
  *
- * Note: PREEMPT_DISABLE_OFFSET is 0 for !PREEMPT_COUNT kernels.
  * Note: See finish_task_switch().
  */
 #define FORK_PREEMPT_COUNT	(2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)
@@ -106,11 +104,7 @@
 /*
  * The preempt_count offset after preempt_disable();
  */
-#if defined(CONFIG_PREEMPT_COUNT)
-# define PREEMPT_DISABLE_OFFSET	PREEMPT_OFFSET
-#else
-# define PREEMPT_DISABLE_OFFSET	0
-#endif
+#define PREEMPT_DISABLE_OFFSET	PREEMPT_OFFSET
 
 /*
  * The preempt_count offset after spin_lock()
@@ -122,8 +116,8 @@
  *
  *  spin_lock_bh()
  *
- * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and
- * softirqs, such that unlock sequences of:
+ * Which need to disable both preemption and softirqs, such that unlock
+ * sequences of:
  *
  *  spin_unlock();
  *  local_bh_enable();
@@ -164,8 +158,6 @@ extern void preempt_count_sub(int val);
 #define preempt_count_inc() preempt_count_add(1)
 #define preempt_count_dec() preempt_count_sub(1)
 
-#ifdef CONFIG_PREEMPT_COUNT
-
 #define preempt_disable() \
 do { \
 	preempt_count_inc(); \
@@ -231,27 +223,6 @@ do { \
 	__preempt_count_dec(); \
 } while (0)
 
-#else /* !CONFIG_PREEMPT_COUNT */
-
-/*
- * Even if we don't have any preemption, we need preempt disable/enable
- * to be barriers, so that we don't have things like get_user/put_user
- * that can cause faults and scheduling migrate into our preempt-protected
- * region.
- */
-#define preempt_disable()			barrier()
-#define sched_preempt_enable_no_resched()	barrier()
-#define preempt_enable_no_resched()		barrier()
-#define preempt_enable()			barrier()
-#define preempt_check_resched()			do { } while (0)
-
-#define preempt_disable_notrace()		barrier()
-#define preempt_enable_no_resched_notrace()	barrier()
-#define preempt_enable_notrace()		barrier()
-#define preemptible()				0
-
-#endif /* CONFIG_PREEMPT_COUNT */
-
 #ifdef MODULE
 /*
  * Modules have no business playing preemption tricks.
-- 
2.20.1