All of lore.kernel.org
 help / color / mirror / Atom feed
From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Sebastian Siewior <bigeasy@linutronix.de>
Subject: [patch 1/8] sched: Clean up the might_sleep() underscore zoo
Date: Thu, 23 Sep 2021 18:54:35 +0200 (CEST)	[thread overview]
Message-ID: <20210923165357.928693482@linutronix.de> (raw)
In-Reply-To: <20210923164145.466686140@linutronix.de>

__might_sleep() vs. ___might_sleep() is hard to distinguish. Aside of that
the three underscore variant is exposed to provide a checkpoint for
rescheduling points which are distinct from blocking points.

They are semantically a preemption point which means that scheduling is
state preserving. A real blocking operation, e.g. mutex_lock(), wait*(),
which cannot preserve a task state which is not equal to RUNNING.

While technically blocking on a "sleeping" spinlock in RT enabled kernels
falls into the voluntary scheduling category because it has to wait until
the contended spin/rw lock becomes available, the RT lock substitution code
can semantically be mapped to a voluntary preemption because the RT lock
substitution code and the scheduler are providing mechanisms to preserve
the task state and to take regular non-lock related wakeups into account.

Rename ___might_sleep() to __might_resched() to make the distinction of
these functions clear.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/kernel.h       |    6 +++---
 include/linux/sched.h        |    8 ++++----
 kernel/locking/spinlock_rt.c |    6 +++---
 kernel/sched/core.c          |    6 +++---
 4 files changed, 13 insertions(+), 13 deletions(-)

--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -111,7 +111,7 @@ static __always_inline void might_resche
 #endif /* CONFIG_PREEMPT_* */
 
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
-extern void ___might_sleep(const char *file, int line, int preempt_offset);
+extern void __might_resched(const char *file, int line, int preempt_offset);
 extern void __might_sleep(const char *file, int line, int preempt_offset);
 extern void __cant_sleep(const char *file, int line, int preempt_offset);
 extern void __cant_migrate(const char *file, int line);
@@ -168,8 +168,8 @@ extern void __cant_migrate(const char *f
  */
 # define non_block_end() WARN_ON(current->non_block_count-- == 0)
 #else
-  static inline void ___might_sleep(const char *file, int line,
-				   int preempt_offset) { }
+  static inline void __might_resched(const char *file, int line,
+				     int preempt_offset) { }
   static inline void __might_sleep(const char *file, int line,
 				   int preempt_offset) { }
 # define might_sleep() do { might_resched(); } while (0)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2041,7 +2041,7 @@ static inline int _cond_resched(void) {
 #endif /* !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) */
 
 #define cond_resched() ({			\
-	___might_sleep(__FILE__, __LINE__, 0);	\
+	__might_resched(__FILE__, __LINE__, 0);	\
 	_cond_resched();			\
 })
 
@@ -2049,9 +2049,9 @@ extern int __cond_resched_lock(spinlock_
 extern int __cond_resched_rwlock_read(rwlock_t *lock);
 extern int __cond_resched_rwlock_write(rwlock_t *lock);
 
-#define cond_resched_lock(lock) ({				\
-	___might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);\
-	__cond_resched_lock(lock);				\
+#define cond_resched_lock(lock) ({					\
+	__might_resched(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);	\
+	__cond_resched_lock(lock);					\
 })
 
 #define cond_resched_rwlock_read(lock) ({			\
--- a/kernel/locking/spinlock_rt.c
+++ b/kernel/locking/spinlock_rt.c
@@ -32,7 +32,7 @@ static __always_inline void rtlock_lock(
 
 static __always_inline void __rt_spin_lock(spinlock_t *lock)
 {
-	___might_sleep(__FILE__, __LINE__, 0);
+	__might_resched(__FILE__, __LINE__, 0);
 	rtlock_lock(&lock->lock);
 	rcu_read_lock();
 	migrate_disable();
@@ -210,7 +210,7 @@ EXPORT_SYMBOL(rt_write_trylock);
 
 void __sched rt_read_lock(rwlock_t *rwlock)
 {
-	___might_sleep(__FILE__, __LINE__, 0);
+	__might_resched(__FILE__, __LINE__, 0);
 	rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
 	rwbase_read_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
 	rcu_read_lock();
@@ -220,7 +220,7 @@ EXPORT_SYMBOL(rt_read_lock);
 
 void __sched rt_write_lock(rwlock_t *rwlock)
 {
-	___might_sleep(__FILE__, __LINE__, 0);
+	__might_resched(__FILE__, __LINE__, 0);
 	rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
 	rwbase_write_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
 	rcu_read_lock();
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9446,11 +9446,11 @@ void __might_sleep(const char *file, int
 			(void *)current->task_state_change,
 			(void *)current->task_state_change);
 
-	___might_sleep(file, line, preempt_offset);
+	__might_resched(file, line, preempt_offset);
 }
 EXPORT_SYMBOL(__might_sleep);
 
-void ___might_sleep(const char *file, int line, int preempt_offset)
+void __might_resched(const char *file, int line, int preempt_offset)
 {
 	/* Ratelimiting timestamp: */
 	static unsigned long prev_jiffy;
@@ -9495,7 +9495,7 @@ void ___might_sleep(const char *file, in
 	dump_stack();
 	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
 }
-EXPORT_SYMBOL(___might_sleep);
+EXPORT_SYMBOL(__might_resched);
 
 void __cant_sleep(const char *file, int line, int preempt_offset)
 {


  reply	other threads:[~2021-09-23 16:54 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-23 16:54 [patch 0/8] sched: Clean up might_sleep() and make it RT aware Thomas Gleixner
2021-09-23 16:54 ` Thomas Gleixner [this message]
2021-10-01 15:05   ` [tip: locking/core] sched: Clean up the might_sleep() underscore zoo tip-bot2 for Thomas Gleixner
2021-09-23 16:54 ` [patch 2/8] sched: Make cond_resched_*lock() variants consistent vs. might_sleep() Thomas Gleixner
2021-10-01 15:05   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2021-09-23 16:54 ` [patch 3/8] sched: Remove preempt_offset argument from __might_sleep() Thomas Gleixner
2021-10-01 15:05   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2021-09-23 16:54 ` [patch 4/8] sched: Cleanup might_sleep() printks Thomas Gleixner
2021-10-01 15:05   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2021-09-23 16:54 ` [patch 5/8] sched: Make might_sleep() output less confusing Thomas Gleixner
2021-10-01 15:05   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2021-09-23 16:54 ` [patch 6/8] sched: Make RCU nest depth distinct in __might_resched() Thomas Gleixner
2021-10-01 15:05   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2021-09-23 16:54 ` [patch 7/8] sched: Make cond_resched_lock() variants RT aware Thomas Gleixner
2021-10-01 15:05   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2021-09-23 16:54 ` [patch 8/8] locking/rt: Take RCU nesting into account for __might_resched() Thomas Gleixner
2021-10-01 15:05   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210923165357.928693482@linutronix.de \
    --to=tglx@linutronix.de \
    --cc=bigeasy@linutronix.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=peterz@infradead.org \
    --subject='Re: [patch 1/8] sched: Clean up the might_sleep() underscore zoo' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.