0,0 → 1,248 |
/* |
* Copyright (C) 2014 Red Hat |
* Author: Rob Clark <robdclark@gmail.com> |
* |
* 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, sublicense, |
* 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 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 NONINFRINGEMENT. IN NO EVENT SHALL |
* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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. |
*/ |
|
#include <drm/drmP.h> |
#include <drm/drm_crtc.h> |
#include <drm/drm_modeset_lock.h> |
|
/** |
* DOC: kms locking |
* |
* As KMS moves toward more fine grained locking, and atomic ioctl where |
* userspace can indirectly control locking order, it becomes necessary |
* to use ww_mutex and acquire-contexts to avoid deadlocks. But because |
* the locking is more distributed around the driver code, we want a bit |
* of extra utility/tracking out of our acquire-ctx. This is provided |
* by drm_modeset_lock / drm_modeset_acquire_ctx. |
* |
* For basic principles of ww_mutex, see: Documentation/ww-mutex-design.txt |
* |
* The basic usage pattern is to: |
* |
* drm_modeset_acquire_init(&ctx) |
* retry: |
* foreach (lock in random_ordered_set_of_locks) { |
* ret = drm_modeset_lock(lock, &ctx) |
* if (ret == -EDEADLK) { |
* drm_modeset_backoff(&ctx); |
* goto retry; |
* } |
* } |
* |
* ... do stuff ... |
* |
* drm_modeset_drop_locks(&ctx); |
* drm_modeset_acquire_fini(&ctx); |
*/ |
|
|
/** |
* drm_modeset_acquire_init - initialize acquire context |
* @ctx: the acquire context |
* @flags: for future |
*/ |
void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, |
uint32_t flags) |
{ |
memset(ctx, 0, sizeof(*ctx)); |
ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
INIT_LIST_HEAD(&ctx->locked); |
} |
EXPORT_SYMBOL(drm_modeset_acquire_init); |
|
/** |
* drm_modeset_acquire_fini - cleanup acquire context |
* @ctx: the acquire context |
*/ |
void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) |
{ |
ww_acquire_fini(&ctx->ww_ctx); |
} |
EXPORT_SYMBOL(drm_modeset_acquire_fini); |
|
/** |
* drm_modeset_drop_locks - drop all locks |
* @ctx: the acquire context |
* |
* Drop all locks currently held against this acquire context. |
*/ |
void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) |
{ |
WARN_ON(ctx->contended); |
while (!list_empty(&ctx->locked)) { |
struct drm_modeset_lock *lock; |
|
lock = list_first_entry(&ctx->locked, |
struct drm_modeset_lock, head); |
|
drm_modeset_unlock(lock); |
} |
} |
EXPORT_SYMBOL(drm_modeset_drop_locks); |
|
static inline int modeset_lock(struct drm_modeset_lock *lock, |
struct drm_modeset_acquire_ctx *ctx, |
bool interruptible, bool slow) |
{ |
int ret; |
|
WARN_ON(ctx->contended); |
|
if (interruptible && slow) { |
ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); |
} else if (interruptible) { |
ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); |
} else if (slow) { |
ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); |
ret = 0; |
} else { |
ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); |
} |
if (!ret) { |
WARN_ON(!list_empty(&lock->head)); |
list_add(&lock->head, &ctx->locked); |
} else if (ret == -EALREADY) { |
/* we already hold the lock.. this is fine. For atomic |
* we will need to be able to drm_modeset_lock() things |
* without having to keep track of what is already locked |
* or not. |
*/ |
ret = 0; |
} else if (ret == -EDEADLK) { |
ctx->contended = lock; |
} |
|
return ret; |
} |
|
static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, |
bool interruptible) |
{ |
struct drm_modeset_lock *contended = ctx->contended; |
|
ctx->contended = NULL; |
|
if (WARN_ON(!contended)) |
return 0; |
|
drm_modeset_drop_locks(ctx); |
|
return modeset_lock(contended, ctx, interruptible, true); |
} |
|
/** |
* drm_modeset_backoff - deadlock avoidance backoff |
* @ctx: the acquire context |
* |
* If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), |
* you must call this function to drop all currently held locks and |
* block until the contended lock becomes available. |
*/ |
void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) |
{ |
modeset_backoff(ctx, false); |
} |
EXPORT_SYMBOL(drm_modeset_backoff); |
|
/** |
* drm_modeset_backoff_interruptible - deadlock avoidance backoff |
* @ctx: the acquire context |
* |
* Interruptible version of drm_modeset_backoff() |
*/ |
int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) |
{ |
return modeset_backoff(ctx, true); |
} |
EXPORT_SYMBOL(drm_modeset_backoff_interruptible); |
|
/** |
* drm_modeset_lock - take modeset lock |
* @lock: lock to take |
* @ctx: acquire ctx |
* |
* If ctx is not NULL, then its ww acquire context is used and the |
* lock will be tracked by the context and can be released by calling |
* drm_modeset_drop_locks(). If -EDEADLK is returned, this means a |
* deadlock scenario has been detected and it is an error to attempt |
* to take any more locks without first calling drm_modeset_backoff(). |
*/ |
int drm_modeset_lock(struct drm_modeset_lock *lock, |
struct drm_modeset_acquire_ctx *ctx) |
{ |
if (ctx) |
return modeset_lock(lock, ctx, false, false); |
|
ww_mutex_lock(&lock->mutex, NULL); |
return 0; |
} |
EXPORT_SYMBOL(drm_modeset_lock); |
|
/** |
* drm_modeset_lock_interruptible - take modeset lock |
* @lock: lock to take |
* @ctx: acquire ctx |
* |
* Interruptible version of drm_modeset_lock() |
*/ |
int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, |
struct drm_modeset_acquire_ctx *ctx) |
{ |
if (ctx) |
return modeset_lock(lock, ctx, true, false); |
|
return ww_mutex_lock_interruptible(&lock->mutex, NULL); |
} |
EXPORT_SYMBOL(drm_modeset_lock_interruptible); |
|
/** |
* drm_modeset_unlock - drop modeset lock |
* @lock: lock to release |
*/ |
void drm_modeset_unlock(struct drm_modeset_lock *lock) |
{ |
list_del_init(&lock->head); |
ww_mutex_unlock(&lock->mutex); |
} |
EXPORT_SYMBOL(drm_modeset_unlock); |
|
/* Temporary.. until we have sufficiently fine grained locking, there |
* are a couple scenarios where it is convenient to grab all crtc locks. |
* It is planned to remove this: |
*/ |
int drm_modeset_lock_all_crtcs(struct drm_device *dev, |
struct drm_modeset_acquire_ctx *ctx) |
{ |
struct drm_mode_config *config = &dev->mode_config; |
struct drm_crtc *crtc; |
int ret = 0; |
|
list_for_each_entry(crtc, &config->crtc_list, head) { |
ret = drm_modeset_lock(&crtc->mutex, ctx); |
if (ret) |
return ret; |
} |
|
return 0; |
} |
EXPORT_SYMBOL(drm_modeset_lock_all_crtcs); |