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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Davidlohr Bueso <dave@stgolabs.net>
Subject: [patch 30/63] locking/spinlock: Provide RT variant
Date: Fri, 30 Jul 2021 15:50:37 +0200	[thread overview]
Message-ID: <20210730135206.865728220@linutronix.de> (raw)
In-Reply-To: <20210730135007.155909613@linutronix.de>

From: Thomas Gleixner <tglx@linutronix.de>

Provide the actual locking functions which make use of the general and
spinlock specific rtmutex code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/locking/Makefile      |    1 
 kernel/locking/spinlock_rt.c |  128 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 kernel/locking/spinlock_rt.c
---
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_LOCK_SPIN_ON_OWNER) += osq_
 obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
 obj-$(CONFIG_QUEUED_SPINLOCKS) += qspinlock.o
 obj-$(CONFIG_RT_MUTEXES) += rtmutex_api.o
+obj-$(CONFIG_PREEMPT_RT) += spinlock_rt.o
 obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
 obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
 obj-$(CONFIG_QUEUED_RWLOCKS) += qrwlock.o
--- /dev/null
+++ b/kernel/locking/spinlock_rt.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PREEMPT_RT substitution for spin/rw_locks
+ *
+ * spin_lock and rw_lock on RT are based on rtmutex with a few twists to
+ * resemble the non RT semantics
+ *
+ * - Contrary to a plain rtmutex, spin_lock and rw_lock are state
+ *   preserving. The task state is saved before blocking on the underlying
+ *   rtmutex and restored when the lock has been acquired. Regular wakeups
+ *   during that time are redirected to the saved state so no wake up is
+ *   missed.
+ *
+ * - Non RT spin/rw_locks disable preemption and evtl. interrupts.
+ *   Disabling preemption has the side effect of disabling migration and
+ *   preventing RCU grace periods.
+ *
+ *   The RT substitutions explicitly disable migration and take
+ *   rcu_read_lock() across the lock held section.
+ */
+#include <linux/spinlock.h>
+#include <linux/export.h>
+
+#define RT_MUTEX_BUILD_SPINLOCKS
+#include "rtmutex.c"
+
+static __always_inline void rtlock_lock(struct rt_mutex_base *rtm)
+{
+	if (unlikely(!rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
+		rtlock_slowlock(rtm);
+}
+
+static __always_inline void __rt_spin_lock(spinlock_t *lock)
+{
+	rtlock_lock(&lock->lock);
+	rcu_read_lock();
+	migrate_disable();
+}
+
+void __sched rt_spin_lock(spinlock_t *lock)
+{
+	spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
+	__rt_spin_lock(lock);
+}
+EXPORT_SYMBOL(rt_spin_lock);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+void __sched rt_spin_lock_nested(spinlock_t *lock, int subclass)
+{
+	spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
+	__rt_spin_lock(lock);
+}
+EXPORT_SYMBOL(rt_spin_lock_nested);
+
+void __sched rt_spin_lock_nest_lock(spinlock_t *lock,
+				    struct lockdep_map *nest_lock)
+{
+	spin_acquire_nest(&lock->dep_map, 0, 0, nest_lock, _RET_IP_);
+	__rt_spin_lock(lock);
+}
+EXPORT_SYMBOL(rt_spin_lock_nest_lock);
+#endif
+
+void __sched rt_spin_unlock(spinlock_t *lock)
+{
+	spin_release(&lock->dep_map, _RET_IP_);
+	migrate_enable();
+	rcu_read_unlock();
+
+	if (unlikely(!rt_mutex_cmpxchg_release(&lock->lock, current, NULL)))
+		rt_mutex_slowunlock(&lock->lock);
+}
+EXPORT_SYMBOL(rt_spin_unlock);
+
+/*
+ * Wait for the lock to get unlocked: instead of polling for an unlock
+ * (like raw spinlocks do), lock and unlock, to force the kernel to
+ * schedule if there's contention:
+ */
+void __sched rt_spin_lock_unlock(spinlock_t *lock)
+{
+	spin_lock(lock);
+	spin_unlock(lock);
+}
+EXPORT_SYMBOL(rt_spin_lock_unlock);
+
+static __always_inline int __rt_spin_trylock(spinlock_t *lock)
+{
+	int ret = 1;
+
+	if (unlikely(!rt_mutex_cmpxchg_acquire(&lock->lock, NULL, current)))
+		ret = rt_mutex_slowtrylock(&lock->lock);
+
+	if (ret) {
+		spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+		rcu_read_lock();
+		migrate_disable();
+	}
+	return ret;
+}
+
+int __sched rt_spin_trylock(spinlock_t *lock)
+{
+	return __rt_spin_trylock(lock);
+}
+EXPORT_SYMBOL(rt_spin_trylock);
+
+int __sched rt_spin_trylock_bh(spinlock_t *lock)
+{
+	int ret;
+
+	local_bh_disable();
+	ret = __rt_spin_trylock(lock);
+	if (!ret)
+		local_bh_enable();
+	return ret;
+}
+EXPORT_SYMBOL(rt_spin_trylock_bh);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+void __rt_spin_lock_init(spinlock_t *lock, const char *name,
+			 struct lock_class_key *key)
+{
+	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
+	lockdep_init_map(&lock->dep_map, name, key, 0);
+}
+EXPORT_SYMBOL(__rt_spin_lock_init);
+#endif


  parent reply	other threads:[~2021-07-30 14:21 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 13:50 [patch 00/63] locking, sched: The PREEMPT-RT locking infrastructure Thomas Gleixner
2021-07-30 13:50 ` [patch 01/63] sched: Split out the wakeup state check Thomas Gleixner
2021-07-30 13:50 ` [patch 02/63] sched: Introduce TASK_RTLOCK_WAIT Thomas Gleixner
2021-07-30 13:50 ` [patch 03/63] sched: Prepare for RT sleeping spin/rwlocks Thomas Gleixner
2021-08-01 15:30   ` Mike Galbraith
2021-08-03  9:48     ` Peter Zijlstra
2021-08-03 14:04       ` Thomas Gleixner
2021-08-03 14:51         ` Peter Zijlstra
2021-08-03 20:11           ` Thomas Gleixner
2021-07-30 13:50 ` [patch 04/63] sched: Rework the __schedule() preempt argument Thomas Gleixner
2021-07-30 13:50 ` [patch 05/63] sched: Provide schedule point for RT locks Thomas Gleixner
2021-07-30 13:50 ` [patch 06/63] sched/wake_q: Provide WAKE_Q_HEAD_INITIALIZER Thomas Gleixner
2021-07-30 13:50 ` [patch 07/63] media/atomisp: Use lockdep instead of *mutex_is_locked() Thomas Gleixner
2021-07-30 13:50 ` [patch 08/63] rtmutex: Remove rt_mutex_is_locked() Thomas Gleixner
2021-07-30 13:50 ` [patch 09/63] rtmutex: Convert macros to inlines Thomas Gleixner
2021-07-30 13:50 ` [patch 10/63] rtmutex: Switch to try_cmpxchg() Thomas Gleixner
2021-07-30 13:50 ` [patch 11/63] rtmutex: Split API and implementation Thomas Gleixner
2021-07-30 13:50 ` [patch 12/63] rtmutex: Split out the inner parts of struct rtmutex Thomas Gleixner
2021-07-30 13:50 ` [patch 13/63] locking/rtmutex: Provide rt_mutex_slowlock_locked() Thomas Gleixner
2021-07-30 13:50 ` [patch 14/63] rtmutex: Provide rt_mutex_base_is_locked() Thomas Gleixner
2021-07-30 13:50 ` [patch 15/63] locking: Add base code for RT rw_semaphore and rwlock Thomas Gleixner
2021-08-04 19:37   ` Waiman Long
2021-08-05  9:04     ` Thomas Gleixner
2021-08-05 14:59       ` Waiman Long
2021-07-30 13:50 ` [patch 16/63] locking/rwsem: Add rtmutex based R/W semaphore implementation Thomas Gleixner
2021-07-30 13:50 ` [patch 17/63] locking/rtmutex: Add wake_state to rt_mutex_waiter Thomas Gleixner
2021-07-30 13:50 ` [patch 18/63] locking/rtmutex: Provide rt_wake_q and helpers Thomas Gleixner
2021-07-30 13:50 ` [patch 19/63] locking/rtmutex: Use rt_mutex_wake_q_head Thomas Gleixner
2021-07-30 13:50 ` [patch 20/63] locking/rtmutex: Prepare RT rt_mutex_wake_q for RT locks Thomas Gleixner
2021-07-30 13:50 ` [patch 21/63] locking/rtmutex: Guard regular sleeping locks specific functions Thomas Gleixner
2021-07-30 13:50 ` [patch 22/63] locking/spinlock: Split the lock types header Thomas Gleixner
2021-08-04 21:17   ` Waiman Long
2021-08-05  8:54     ` Thomas Gleixner
2021-07-30 13:50 ` [patch 23/63] locking/rtmutex: Prevent future include recursion hell Thomas Gleixner
2021-07-30 13:50 ` [patch 24/63] locking/lockdep: Reduce includes in debug_locks.h Thomas Gleixner
2021-07-30 13:50 ` [patch 25/63] rbtree: Split out the rbtree type definitions Thomas Gleixner
2021-07-30 13:50 ` [patch 26/63] locking/rtmutex: Include only rbtree types Thomas Gleixner
2021-07-30 13:50 ` [patch 27/63] locking/spinlock: Provide RT specific spinlock type Thomas Gleixner
2021-07-30 13:50 ` [patch 28/63] locking/spinlock: Provide RT variant header Thomas Gleixner
2021-07-30 13:50 ` [patch 29/63] locking/rtmutex: Provide the spin/rwlock core lock function Thomas Gleixner
2021-07-30 13:50 ` Thomas Gleixner [this message]
2021-08-04 23:34   ` [patch 30/63] locking/spinlock: Provide RT variant Waiman Long
2021-08-05  8:54     ` Thomas Gleixner
2021-07-30 13:50 ` [patch 31/63] locking/rwlock: " Thomas Gleixner
2021-07-30 13:50 ` [patch 32/63] locking/mutex: Consolidate core headers Thomas Gleixner
2021-07-30 13:50 ` [patch 33/63] locking/mutex: Move waiter to core header Thomas Gleixner
2021-07-30 13:50 ` [patch 34/63] locking/ww_mutex: Move ww_mutex declarations into ww_mutex.h Thomas Gleixner
2021-07-30 13:50 ` [patch 35/63] locking/mutex: Make mutex::wait_lock raw Thomas Gleixner
2021-07-30 13:50 ` [patch 36/63] locking/ww_mutex: Simplify lockdep annotation Thomas Gleixner
2021-07-30 13:50 ` [patch 37/63] locking/ww_mutex: Gather mutex_waiter initialization Thomas Gleixner
2021-07-30 13:50 ` [patch 38/63] locking/ww_mutex: Split up ww_mutex_unlock() Thomas Gleixner
2021-07-30 13:50 ` [patch 39/63] locking/ww_mutex: Split W/W implementation logic Thomas Gleixner
2021-07-30 13:50 ` [patch 40/63] locking/ww_mutex: Remove __sched annotation Thomas Gleixner
2021-07-30 13:50 ` [patch 41/63] locking/ww_mutex: Abstract waiter iteration Thomas Gleixner
2021-07-30 13:50 ` [patch 42/63] locking/ww_mutex: Abstract waiter enqueueing Thomas Gleixner
2021-07-30 13:50 ` [patch 43/63] locking/ww_mutex: Abstract mutex accessors Thomas Gleixner
2021-07-30 13:50 ` [patch 44/63] locking/ww_mutex: Abstract mutex types Thomas Gleixner
2021-07-30 13:50 ` [patch 45/63] locking/ww_mutex: Abstract internal lock access Thomas Gleixner
2021-07-30 13:50 ` [patch 46/63] locking/ww_mutex: Implement rt_mutex accessors Thomas Gleixner
2021-07-30 13:50 ` [patch 47/63] locking/ww_mutex: Add RT priority to W/W order Thomas Gleixner
2021-07-30 13:50 ` [patch 48/63] locking/ww_mutex: Add rt_mutex based lock type and accessors Thomas Gleixner
2021-07-30 13:50 ` [patch 49/63] locking/rtmutex: Extend the rtmutex core to support ww_mutex Thomas Gleixner
2021-07-30 13:50 ` [patch 50/63] locking/ww_mutex: Implement rtmutex based ww_mutex API functions Thomas Gleixner
2021-07-31 13:26   ` Mike Galbraith
2021-08-01 21:18     ` Thomas Gleixner
2021-07-30 13:50 ` [patch 51/63] locking/rtmutex: Add mutex variant for RT Thomas Gleixner
2021-07-30 13:50 ` [patch 52/63] lib/test_lockup: Adapt to changed variables Thomas Gleixner
2021-07-30 13:51 ` [patch 53/63] futex: Validate waiter correctly in futex_proxy_trylock_atomic() Thomas Gleixner
2021-07-30 13:51 ` [patch 54/63] futex: Cleanup stale comments Thomas Gleixner
2021-07-30 13:51 ` [patch 55/63] futex: Correct the number of requeued waiters for PI Thomas Gleixner
2021-07-30 13:51 ` [patch 56/63] futex: Restructure futex_requeue() Thomas Gleixner
2021-07-30 13:51 ` [patch 57/63] futex: Clarify comment in futex_requeue() Thomas Gleixner
2021-07-30 13:51 ` [patch 58/63] futex: Prevent requeue_pi() lock nesting issue on RT Thomas Gleixner
2021-08-02 12:56   ` Peter Zijlstra
2021-08-02 13:10     ` Peter Zijlstra
2021-08-02 14:35       ` Thomas Gleixner
2021-08-02 14:34     ` Thomas Gleixner
2021-08-03 10:28     ` Peter Zijlstra
2021-08-03 21:10       ` Thomas Gleixner
2021-08-03 10:07   ` Peter Zijlstra
2021-08-03 21:10     ` Thomas Gleixner
2021-08-03 11:20   ` Peter Zijlstra
2021-08-03 21:22     ` Thomas Gleixner
2021-07-30 13:51 ` [patch 59/63] rtmutex: Prevent lockdep false positive with PI futexes Thomas Gleixner
2021-07-30 13:51 ` [patch 60/63] preempt: Adjust PREEMPT_LOCK_OFFSET for RT Thomas Gleixner
2021-07-30 13:51 ` [patch 61/63] locking/rtmutex: Implement equal priority lock stealing Thomas Gleixner
2021-07-30 13:51 ` [patch 62/63] locking/rtmutex: Add adaptive spinwait mechanism Thomas Gleixner
2021-08-04 12:30   ` Peter Zijlstra
2021-08-04 17:49     ` Thomas Gleixner
2021-07-30 13:51 ` [patch 63/63] locking/rtmutex: Use adaptive spinwait for all rtmutex based locks Thomas Gleixner
     [not found] ` <20210803063217.2325-1-hdanton@sina.com>
2021-08-03  9:10   ` [patch 30/63] locking/spinlock: Provide RT variant Thomas Gleixner
2021-08-03 12:37 ` [patch 00/63] locking, sched: The PREEMPT-RT locking infrastructure Daniel Bristot de Oliveira

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