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Commit 1f8083c6 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull locking fixes from Ingo Molnar:
 "Misc fixes: lockstat fix, futex fix on !MMU systems, big endian fix
  for qrwlocks and a race fix for pvqspinlocks"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/pvqspinlock: Fix a bug in qstat_read()
  locking/pvqspinlock: Fix double hash race
  locking/qrwlock: Fix write unlock bug on big endian systems
  futex: Assume all mappings are private on !MMU systems
parents 25db6918 c2ace36b

include/asm-generic/qrwlock.h

+25 −2
Original line number Diff line number Diff line
@@ -25,7 +25,20 @@ 
#include <asm-generic/qrwlock_types.h>



/*

 * Writer states & reader shift and bias

 * Writer states & reader shift and bias.

 *

 *       | +0 | +1 | +2 | +3 |

 *   ----+----+----+----+----+

 *    LE | 78 | 56 | 34 | 12 | 0x12345678

 *   ----+----+----+----+----+

 *       | wr |      rd      |

 *       +----+----+----+----+

 *

 *   ----+----+----+----+----+

 *    BE | 12 | 34 | 56 | 78 | 0x12345678

 *   ----+----+----+----+----+

 *       |      rd      | wr |

 *       +----+----+----+----+

 */

#define	_QW_WAITING	1		/* A writer is waiting	   */

#define	_QW_LOCKED	0xff		/* A writer holds the lock */
@@ -133,13 +146,23 @@ static inline void queued_read_unlock(struct qrwlock *lock) 
	(void)atomic_sub_return_release(_QR_BIAS, &lock->cnts);

}



/**

 * __qrwlock_write_byte - retrieve the write byte address of a queue rwlock

 * @lock : Pointer to queue rwlock structure

 * Return: the write byte address of a queue rwlock

 */

static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)

{

	return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);

}



/**

 * queued_write_unlock - release write lock of a queue rwlock

 * @lock : Pointer to queue rwlock structure

 */

static inline void queued_write_unlock(struct qrwlock *lock)

{

	smp_store_release((u8 *)&lock->cnts, 0);

	smp_store_release(__qrwlock_write_byte(lock), 0);

}



/*

kernel/futex.c

+22 −1
Original line number Diff line number Diff line
@@ -179,7 +179,15 @@ int __read_mostly futex_cmpxchg_enabled; 
 * Futex flags used to encode options to functions and preserve them across

 * restarts.

 */

#ifdef CONFIG_MMU

# define FLAGS_SHARED		0x01

#else

/*

 * NOMMU does not have per process address space. Let the compiler optimize

 * code away.

 */

# define FLAGS_SHARED		0x00

#endif

#define FLAGS_CLOCKRT		0x02

#define FLAGS_HAS_TIMEOUT	0x04
@@ -405,6 +413,16 @@ static void get_futex_key_refs(union futex_key *key) 
	if (!key->both.ptr)

		return;



	/*

	 * On MMU less systems futexes are always "private" as there is no per

	 * process address space. We need the smp wmb nevertheless - yes,

	 * arch/blackfin has MMU less SMP ...

	 */

	if (!IS_ENABLED(CONFIG_MMU)) {

		smp_mb(); /* explicit smp_mb(); (B) */

		return;

	}



	switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {

	case FUT_OFF_INODE:

		ihold(key->shared.inode); /* implies smp_mb(); (B) */
@@ -436,6 +454,9 @@ static void drop_futex_key_refs(union futex_key *key) 
		return;

	}



	if (!IS_ENABLED(CONFIG_MMU))

		return;



	switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {

	case FUT_OFF_INODE:

		iput(key->shared.inode);

kernel/locking/qspinlock_paravirt.h

+1 −1
Original line number Diff line number Diff line
@@ -450,7 +450,7 @@ pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node) 
				goto gotlock;

			}

		}

		WRITE_ONCE(pn->state, vcpu_halted);

		WRITE_ONCE(pn->state, vcpu_hashed);

		qstat_inc(qstat_pv_wait_head, true);

		qstat_inc(qstat_pv_wait_again, waitcnt);

		pv_wait(&l->locked, _Q_SLOW_VAL);

kernel/locking/qspinlock_stat.h

+0 −1
Original line number Diff line number Diff line
@@ -153,7 +153,6 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf, 
		 */

		if ((counter == qstat_pv_latency_kick) ||

		    (counter == qstat_pv_latency_wake)) {

			stat = 0;

			if (kicks)

				stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);

		}