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authorLinus Torvalds <torvalds@linux-foundation.org>2009-12-12 17:46:33 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-12 17:46:33 -0500
commitf01eb3640308c005d31b29d0a8bc2b7acb4e3f75 (patch)
treea4e249cc4b5880b841487c889c32be8b5414fd11 /tools/perf/util
parent6698e34720660e18b45e2e3b115ee4584d0c3b5e (diff)
[BKL] add 'might_sleep()' to the outermost lock taker
As shown by the previous patch (6698e3472: "tty: Fix BKL taken under a spinlock bug introduced in the BKL split") the BKL removal is prone to some subtle issues, where removing the BKL in one place may in fact make a previously nested BKL call the new outer call, and then prone to nasty deadlocks with other spinlocks. In general, we should never take the BKL while we're holding a spinlock, so let's just add a "might_sleep()" to it (even though the BKL doesn't technically sleep - at least not yet), and we'll get nice warnings the next time this kind of problem happens during BKL removal. Acked-and-Tested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'tools/perf/util')
0 files changed, 0 insertions, 0 deletions
generated by cgit v1.2.2 (git 2.25.0) at 2025-08-26 06:33:30 -0400
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/*
 * Hardware spinlock public header
 *
 * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
 *
 * Contact: Ohad Ben-Cohen <ohad@wizery.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#ifndef __LINUX_HWSPINLOCK_H
#define __LINUX_HWSPINLOCK_H

#include <linux/err.h>
#include <linux/sched.h>

/* hwspinlock mode argument */
#define HWLOCK_IRQSTATE	0x01	/* Disable interrupts, save state */
#define HWLOCK_IRQ	0x02	/* Disable interrupts, don't save state */

struct hwspinlock;

#if defined(CONFIG_HWSPINLOCK) || defined(CONFIG_HWSPINLOCK_MODULE)

int hwspin_lock_register(struct hwspinlock *lock);
struct hwspinlock *hwspin_lock_unregister(unsigned int id);
struct hwspinlock *hwspin_lock_request(void);
struct hwspinlock *hwspin_lock_request_specific(unsigned int id);
int hwspin_lock_free(struct hwspinlock *hwlock);
int hwspin_lock_get_id(struct hwspinlock *hwlock);
int __hwspin_lock_timeout(struct hwspinlock *, unsigned int, int,
							unsigned long *);
int __hwspin_trylock(struct hwspinlock *, int, unsigned long *);
void __hwspin_unlock(struct hwspinlock *, int, unsigned long *);

#else /* !CONFIG_HWSPINLOCK */

/*
 * We don't want these functions to fail if CONFIG_HWSPINLOCK is not
 * enabled. We prefer to silently succeed in this case, and let the
 * code path get compiled away. This way, if CONFIG_HWSPINLOCK is not
 * required on a given setup, users will still work.
 *
 * The only exception is hwspin_lock_register/hwspin_lock_unregister, with which
 * we _do_ want users to fail (no point in registering hwspinlock instances if
 * the framework is not available).
 *
 * Note: ERR_PTR(-ENODEV) will still be considered a success for NULL-checking
 * users. Others, which care, can still check this with IS_ERR.
 */
static inline struct hwspinlock *hwspin_lock_request(void)
{
	return ERR_PTR(-ENODEV);
}

static inline struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
{
	return ERR_PTR(-ENODEV);
}

static inline int hwspin_lock_free(struct hwspinlock *hwlock)
{
	return 0;
}

static inline
int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
					int mode, unsigned long *flags)
{
	return 0;
}

static inline
int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
{
	return 0;
}

static inline
void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
{
	return 0;
}

static inline int hwspin_lock_get_id(struct hwspinlock *hwlock)
{
	return 0;
}

static inline int hwspin_lock_register(struct hwspinlock *hwlock)
{
	return -ENODEV;
}

static inline struct hwspinlock *hwspin_lock_unregister(unsigned int id)
{
	return NULL;
}

#endif /* !CONFIG_HWSPINLOCK */

/**
 * hwspin_trylock_irqsave() - try to lock an hwspinlock, disable interrupts
 * @hwlock: an hwspinlock which we want to trylock
 * @flags: a pointer to where the caller's interrupt state will be saved at
 *
 * This function attempts to lock the underlying hwspinlock, and will
 * immediately fail if the hwspinlock is already locked.
 *
 * Upon a successful return from this function, preemption and local
 * interrupts are disabled (previous interrupts state is saved at @flags),
 * so the caller must not sleep, and is advised to release the hwspinlock
 * as soon as possible.
 *
 * Returns 0 if we successfully locked the hwspinlock, -EBUSY if
 * the hwspinlock was already taken, and -EINVAL if @hwlock is invalid.
 */
static inline
int hwspin_trylock_irqsave(struct hwspinlock *hwlock, unsigned long *flags)
{
	return __hwspin_trylock(hwlock, HWLOCK_IRQSTATE, flags);
}

/**