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/**************************************************************************
*
* Copyright (c) 2007-2008 Tungsten Graphics, Inc., Cedar Park, TX., USA
* All Rights Reserved.
* Copyright (c) 2009 VMware, Inc., Palo Alto, CA., USA
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sub license, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial portions
* of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
*
**************************************************************************/
/*
* Authors: Thomas Hellstrom <thomas-at-tungstengraphics-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 is fast, and
* intended for in-kernel use only.
* Taking it in write mode is slow.
*
* The write 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 write lock held.
* If a user-space process dies while having the write-lock,
* it will be released during the file descriptor release.
*
* The read lock is typically placed at the start of an IOCTL- or
* user-space callable function that may end up allocating a memory area.
* This includes setstatus, super-ioctls and faults; the latter may move
* unmappable regions to mappable. It's a bug to leave kernel space with the
* read lock held.
*
* Both read- and write lock taking is interruptible for low signal-delivery
* latency. The locking functions will return -ERESTART if interrupted by a
* signal.
*
* Locking order: The lock should be taken BEFORE any TTM mutexes
* or spinlocks.
*
* Typical usages:
* a) VT-switching, when we want to clean VRAM and perhaps AGP. The lock
* stops it from being repopulated.
* b) out-of-VRAM or out-of-aperture space, in which case the process
* receiving the out-of-space notification may take the lock in write mode
* and evict all buffers prior to start validating its own buffers.
*/
#ifndef _TTM_LOCK_H_
#define _TTM_LOCK_H_
#include "ttm_object.h"
#include <linux/wait.h>
#include <asm/atomic.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.
* @write_lock_pending: Flag indicating that a write-lock is pending. Avoids
* write lock starvation.
* @readers: The lock status: A negative number indicates that a write lock is
* held. Positive values indicate number of concurrent readers.
*/
struct ttm_lock {
struct ttm_base_object base;
wait_queue_head_t queue;
atomic_t write_lock_pending;
atomic_t readers;
bool kill_takers;
int signal;
};
/**
* 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_unlock
*
* @lock: Pointer to a struct ttm_lock
* @interruptible: Interruptible sleeping while waiting for a lock.
*
* Takes the lock in read mode.
* Returns:
* -ERESTART If interrupted by a signal and interruptible is true.
*/
extern int ttm_read_lock(struct ttm_lock *lock, bool interruptible);
/**
* ttm_write_lock
*
* @lock: Pointer to a struct ttm_lock
* @interruptible: Interruptible sleeping while waiting for a lock.
* @tfile: Pointer to a struct ttm_object_file used to identify the user-space
* application taking the lock.
*
* Takes the lock in write mode.
* Returns:
* -ERESTART If interrupted by a signal and interruptible is true.
* -ENOMEM: Out of memory when locking.
*/
extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible,
struct ttm_object_file *tfile);
/**
* ttm_write_unlock
*
* @lock: Pointer to a struct ttm_lock
* @tfile: Pointer to a struct ttm_object_file used to identify the user-space
* application taking the lock.
*
* Releases a write lock.
* Returns:
* -EINVAL If the lock was not held.
*/
extern int ttm_write_unlock(struct ttm_lock *lock,
struct ttm_object_file *tfile);
/**
* 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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