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*
* Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
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/*
* Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
*/
/** @file ttm_lock.h
* This file implements a simple replacement for the buffer manager use
* of the DRM heavyweight hardware lock.
* The lock is a read-write lock. Taking it in read mode and write mode
* is relatively fast, and intended for in-kernel use only.
*
* The vt mode is used only when there is a need to block all
* user-space processes from validating buffers.
* It's allowed to leave kernel space with the vt lock held.
* If a user-space process dies while having the vt-lock,
* it will be released during the file descriptor release. The vt lock
* excludes write lock and read lock.
*
* The suspend mode is used to lock out all TTM users when preparing for
* and executing suspend operations.
*
*/
#ifndef _TTM_LOCK_H_
#define _TTM_LOCK_H_
#include <linux/wait.h>
#include <linux/atomic.h>
#include "ttm_object.h"
/**
* struct ttm_lock
*
* @base: ttm base object used solely to release the lock if the client
* holding the lock dies.
* @queue: Queue for processes waiting for lock change-of-status.
* @lock: Spinlock protecting some lock members.
* @rw: Read-write lock counter. Protected by @lock.
* @flags: Lock state. Protected by @lock.
* @kill_takers: Boolean whether to kill takers of the lock.
* @signal: Signal to send when kill_takers is true.
*/
struct ttm_lock {
struct ttm_base_object base;
wait_queue_head_t queue;
spinlock_t lock;
int32_t rw;
uint32_t flags;
bool kill_takers;
int signal;
struct ttm_object_file *vt_holder;
};
/**
* ttm_lock_init
*
* @lock: Pointer to a struct ttm_lock
* Initializes the lock.
*/
extern void ttm_lock_init(struct ttm_lock *lock);
/**
* ttm_read_unlock
*
* @lock: Pointer to a struct ttm_lock
*
* Releases a read lock.
*/
extern void ttm_read_unlock(struct ttm_lock *lock);
/**
* ttm_read_lock
*
* @lock: Pointer to a struct ttm_lock
* @interruptible: Interruptible sleeping while waiting for a lock.
*
* Takes the lock in read mode.
* Returns:
* -ERESTARTSYS If interrupted by a signal and interruptible is true.
*/
extern int ttm_read_lock(struct ttm_lock *lock, bool interruptible);
/**
* ttm_read_trylock
*
* @lock: Pointer to a struct ttm_lock
* @interruptible: Interruptible sleeping while waiting for a lock.
*
* Tries to take the lock in read mode. If the lock is already held
* in write mode, the function will return -EBUSY. If the lock is held
* in vt or suspend mode, the function will sleep until these modes
* are unlocked.
*
* Returns:
* -EBUSY The lock was already held in write mode.
* -ERESTARTSYS If interrupted by a signal and interruptible is true.
*/
extern int ttm_read_trylock(struct ttm_lock *lock, bool interruptible);
/**
* ttm_write_unlock
*
* @lock: Pointer to a struct ttm_lock
*
* Releases a write lock.
*/
extern void ttm_write_unlock(struct ttm_lock *lock);
/**
* ttm_write_lock
*
* @lock: Pointer to a struct ttm_lock
* @interruptible: Interruptible sleeping while waiting for a lock.
*
* Takes the lock in write mode.
* Returns:
* -ERESTARTSYS If interrupted by a signal and interruptible is true.
*/
extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
/**
* ttm_lock_downgrade
*
* @lock: Pointer to a struct ttm_lock
*
* Downgrades a write lock to a read lock.
*/
extern void ttm_lock_downgrade(struct ttm_lock *lock);
/**
* ttm_suspend_lock
*
* @lock: Pointer to a struct ttm_lock
*
* Takes the lock in suspend mode. Excludes read and write mode.
*/
extern void ttm_suspend_lock(struct ttm_lock *lock);
/**
* ttm_suspend_unlock
*
* @lock: Pointer to a struct ttm_lock
*
* Releases a suspend lock
*/
extern void ttm_suspend_unlock(struct ttm_lock *lock);
/**
* ttm_vt_lock
*
* @lock: Pointer to a struct ttm_lock
* @interruptible: Interruptible sleeping while waiting for a lock.
* @tfile: Pointer to a struct ttm_object_file to register the lock with.
*
* Takes the lock in vt mode.
* Returns:
* -ERESTARTSYS If interrupted by a signal and interruptible is true.
* -ENOMEM: Out of memory when locking.
*/
extern int ttm_vt_lock(struct ttm_lock *lock, bool interruptible,
struct ttm_object_file *tfile);
/**
* ttm_vt_unlock
*
* @lock: Pointer to a struct ttm_lock
*
* Releases a vt lock.
* Returns:
* -EINVAL If the lock was not held.
*/
extern int ttm_vt_unlock(struct ttm_lock *lock);
/**
* ttm_write_unlock
*
* @lock: Pointer to a struct ttm_lock
*
* Releases a write lock.
*/
extern void ttm_write_unlock(struct ttm_lock *lock);
/**
* ttm_write_lock
*
* @lock: Pointer to a struct ttm_lock
* @interruptible: Interruptible sleeping while waiting for a lock.
*
* Takes the lock in write mode.
* Returns:
* -ERESTARTSYS If interrupted by a signal and interruptible is true.
*/
extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
/**
* ttm_lock_set_kill
*
* @lock: Pointer to a struct ttm_lock
* @val: Boolean whether to kill processes taking the lock.
* @signal: Signal to send to the process taking the lock.
*
* The kill-when-taking-lock functionality is used to kill processes that keep
* on using the TTM functionality when its resources has been taken down, for
* example when the X server exits. A typical sequence would look like this:
* - X server takes lock in write mode.
* - ttm_lock_set_kill() is called with @val set to true.
* - As part of X server exit, TTM resources are taken down.
* - X server releases the lock on file release.
* - Another dri client wants to render, takes the lock and is killed.
*
*/
static inline void ttm_lock_set_kill(struct ttm_lock *lock, bool val,
int signal)
{
lock->kill_takers = val;
if (val)
lock->signal = signal;
}
#endif
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