linux-kernel - [GIT PULL] locking fixes

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Date:   Tue, 17 Dec 2019 12:27:19 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] locking fixes

Linus,

Please pull the latest locking-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus

   # HEAD: c571b72e2b845ca0519670cb7c4b5fe5f56498a5 Revert "locking/mutex: Complain upon mutex API misuse in IRQ contexts"

Tone down mutex debugging complaints, and annotate/fix spinlock debugging 
data accesses for KCSAN.

 Thanks,

	Ingo

------------------>
Davidlohr Bueso (1):
      Revert "locking/mutex: Complain upon mutex API misuse in IRQ contexts"

Marco Elver (1):
      locking/spinlock/debug: Fix various data races


 kernel/locking/mutex.c          |  4 ----
 kernel/locking/spinlock_debug.c | 32 ++++++++++++++++----------------
 2 files changed, 16 insertions(+), 20 deletions(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 54cc5f9286e9..5352ce50a97e 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -733,9 +733,6 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
  */
 void __sched mutex_unlock(struct mutex *lock)
 {
-#ifdef CONFIG_DEBUG_MUTEXES
-	WARN_ON(in_interrupt());
-#endif
 #ifndef CONFIG_DEBUG_LOCK_ALLOC
 	if (__mutex_unlock_fast(lock))
 		return;
@@ -1416,7 +1413,6 @@ int __sched mutex_trylock(struct mutex *lock)
 
 #ifdef CONFIG_DEBUG_MUTEXES
 	DEBUG_LOCKS_WARN_ON(lock->magic != lock);
-	WARN_ON(in_interrupt());
 #endif
 
 	locked = __mutex_trylock(lock);
diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c
index 399669f7eba8..472dd462a40c 100644
--- a/kernel/locking/spinlock_debug.c
+++ b/kernel/locking/spinlock_debug.c
@@ -51,19 +51,19 @@ EXPORT_SYMBOL(__rwlock_init);
 
 static void spin_dump(raw_spinlock_t *lock, const char *msg)
 {
-	struct task_struct *owner = NULL;
+	struct task_struct *owner = READ_ONCE(lock->owner);
 
-	if (lock->owner && lock->owner != SPINLOCK_OWNER_INIT)
-		owner = lock->owner;
+	if (owner == SPINLOCK_OWNER_INIT)
+		owner = NULL;
 	printk(KERN_EMERG "BUG: spinlock %s on CPU#%d, %s/%d\n",
 		msg, raw_smp_processor_id(),
 		current->comm, task_pid_nr(current));
 	printk(KERN_EMERG " lock: %pS, .magic: %08x, .owner: %s/%d, "
 			".owner_cpu: %d\n",
-		lock, lock->magic,
+		lock, READ_ONCE(lock->magic),
 		owner ? owner->comm : "<none>",
 		owner ? task_pid_nr(owner) : -1,
-		lock->owner_cpu);
+		READ_ONCE(lock->owner_cpu));
 	dump_stack();
 }
 
@@ -80,16 +80,16 @@ static void spin_bug(raw_spinlock_t *lock, const char *msg)
 static inline void
 debug_spin_lock_before(raw_spinlock_t *lock)
 {
-	SPIN_BUG_ON(lock->magic != SPINLOCK_MAGIC, lock, "bad magic");
-	SPIN_BUG_ON(lock->owner == current, lock, "recursion");
-	SPIN_BUG_ON(lock->owner_cpu == raw_smp_processor_id(),
+	SPIN_BUG_ON(READ_ONCE(lock->magic) != SPINLOCK_MAGIC, lock, "bad magic");
+	SPIN_BUG_ON(READ_ONCE(lock->owner) == current, lock, "recursion");
+	SPIN_BUG_ON(READ_ONCE(lock->owner_cpu) == raw_smp_processor_id(),
 							lock, "cpu recursion");
 }
 
 static inline void debug_spin_lock_after(raw_spinlock_t *lock)
 {
-	lock->owner_cpu = raw_smp_processor_id();
-	lock->owner = current;
+	WRITE_ONCE(lock->owner_cpu, raw_smp_processor_id());
+	WRITE_ONCE(lock->owner, current);
 }
 
 static inline void debug_spin_unlock(raw_spinlock_t *lock)
@@ -99,8 +99,8 @@ static inline void debug_spin_unlock(raw_spinlock_t *lock)
 	SPIN_BUG_ON(lock->owner != current, lock, "wrong owner");
 	SPIN_BUG_ON(lock->owner_cpu != raw_smp_processor_id(),
 							lock, "wrong CPU");
-	lock->owner = SPINLOCK_OWNER_INIT;
-	lock->owner_cpu = -1;
+	WRITE_ONCE(lock->owner, SPINLOCK_OWNER_INIT);
+	WRITE_ONCE(lock->owner_cpu, -1);
 }
 
 /*
@@ -187,8 +187,8 @@ static inline void debug_write_lock_before(rwlock_t *lock)
 
 static inline void debug_write_lock_after(rwlock_t *lock)
 {
-	lock->owner_cpu = raw_smp_processor_id();
-	lock->owner = current;
+	WRITE_ONCE(lock->owner_cpu, raw_smp_processor_id());
+	WRITE_ONCE(lock->owner, current);
 }
 
 static inline void debug_write_unlock(rwlock_t *lock)
@@ -197,8 +197,8 @@ static inline void debug_write_unlock(rwlock_t *lock)
 	RWLOCK_BUG_ON(lock->owner != current, lock, "wrong owner");
 	RWLOCK_BUG_ON(lock->owner_cpu != raw_smp_processor_id(),
 							lock, "wrong CPU");
-	lock->owner = SPINLOCK_OWNER_INIT;
-	lock->owner_cpu = -1;
+	WRITE_ONCE(lock->owner, SPINLOCK_OWNER_INIT);
+	WRITE_ONCE(lock->owner_cpu, -1);
 }
 
 void do_raw_write_lock(rwlock_t *lock)