linux-stable/drivers/gpu/drm/drm_modeset_lock.c
Daniel Vetter b260ac3ebe drm: Remove drm_modeset_legacy_acquire_ctx and crtc->acquire_ctx
With all the callers of drm_modeset_lock_crtc gone, and all the places
it was formerly used properly wiring the acquire ctx through, we can
remove this.

The only hidden context magic we still have is now the global one.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170403083304.9083-4-daniel.vetter@ffwll.ch
2017-04-05 09:26:45 +02:00

404 lines
11 KiB
C

/*
* 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 &struct drm_modeset_lock and &struct drm_modeset_acquire_ctx.
*
* For basic principles of &ww_mutex, see: Documentation/locking/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);
*
* On top of of these per-object locks using &ww_mutex there's also an overall
* &drm_mode_config.mutex, for protecting everything else. Mostly this means
* probe state of connectors, and preventing hotplug add/removal of connectors.
*
* Finally there's a bunch of dedicated locks to protect drm core internal
* lists and lookup data structures.
*/
static DEFINE_WW_CLASS(crtc_ww_class);
/**
* drm_modeset_lock_all - take all modeset locks
* @dev: DRM device
*
* This function takes all modeset locks, suitable where a more fine-grained
* scheme isn't (yet) implemented. Locks must be dropped by calling the
* drm_modeset_unlock_all() function.
*
* This function is deprecated. It allocates a lock acquisition context and
* stores it in &drm_device.mode_config. This facilitate conversion of
* existing code because it removes the need to manually deal with the
* acquisition context, but it is also brittle because the context is global
* and care must be taken not to nest calls. New code should use the
* drm_modeset_lock_all_ctx() function and pass in the context explicitly.
*/
void drm_modeset_lock_all(struct drm_device *dev)
{
struct drm_mode_config *config = &dev->mode_config;
struct drm_modeset_acquire_ctx *ctx;
int ret;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (WARN_ON(!ctx))
return;
mutex_lock(&config->mutex);
drm_modeset_acquire_init(ctx, 0);
retry:
ret = drm_modeset_lock_all_ctx(dev, ctx);
if (ret < 0) {
if (ret == -EDEADLK) {
drm_modeset_backoff(ctx);
goto retry;
}
drm_modeset_acquire_fini(ctx);
kfree(ctx);
return;
}
WARN_ON(config->acquire_ctx);
/*
* We hold the locks now, so it is safe to stash the acquisition
* context for drm_modeset_unlock_all().
*/
config->acquire_ctx = ctx;
drm_warn_on_modeset_not_all_locked(dev);
}
EXPORT_SYMBOL(drm_modeset_lock_all);
/**
* drm_modeset_unlock_all - drop all modeset locks
* @dev: DRM device
*
* This function drops all modeset locks taken by a previous call to the
* drm_modeset_lock_all() function.
*
* This function is deprecated. It uses the lock acquisition context stored
* in &drm_device.mode_config. This facilitates conversion of existing
* code because it removes the need to manually deal with the acquisition
* context, but it is also brittle because the context is global and care must
* be taken not to nest calls. New code should pass the acquisition context
* directly to the drm_modeset_drop_locks() function.
*/
void drm_modeset_unlock_all(struct drm_device *dev)
{
struct drm_mode_config *config = &dev->mode_config;
struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;
if (WARN_ON(!ctx))
return;
config->acquire_ctx = NULL;
drm_modeset_drop_locks(ctx);
drm_modeset_acquire_fini(ctx);
kfree(ctx);
mutex_unlock(&dev->mode_config.mutex);
}
EXPORT_SYMBOL(drm_modeset_unlock_all);
/**
* drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
* @dev: device
*
* Useful as a debug assert.
*/
void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
{
struct drm_crtc *crtc;
/* Locking is currently fubar in the panic handler. */
if (oops_in_progress)
return;
drm_for_each_crtc(crtc, dev)
WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
}
EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
/**
* 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 (ctx->trylock_only) {
lockdep_assert_held(&ctx->ww_ctx);
if (!ww_mutex_trylock(&lock->mutex))
return -EBUSY;
else
return 0;
} else 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_init - initialize lock
* @lock: lock to init
*/
void drm_modeset_lock_init(struct drm_modeset_lock *lock)
{
ww_mutex_init(&lock->mutex, &crtc_ww_class);
INIT_LIST_HEAD(&lock->head);
}
EXPORT_SYMBOL(drm_modeset_lock_init);
/**
* 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);
/**
* drm_modeset_lock_all_ctx - take all modeset locks
* @dev: DRM device
* @ctx: lock acquisition context
*
* This function takes all modeset locks, suitable where a more fine-grained
* scheme isn't (yet) implemented.
*
* Unlike drm_modeset_lock_all(), it doesn't take the &drm_mode_config.mutex
* since that lock isn't required for modeset state changes. Callers which
* need to grab that lock too need to do so outside of the acquire context
* @ctx.
*
* Locks acquired with this function should be released by calling the
* drm_modeset_drop_locks() function on @ctx.
*
* Returns: 0 on success or a negative error-code on failure.
*/
int drm_modeset_lock_all_ctx(struct drm_device *dev,
struct drm_modeset_acquire_ctx *ctx)
{
struct drm_crtc *crtc;
struct drm_plane *plane;
int ret;
ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
if (ret)
return ret;
drm_for_each_crtc(crtc, dev) {
ret = drm_modeset_lock(&crtc->mutex, ctx);
if (ret)
return ret;
}
drm_for_each_plane(plane, dev) {
ret = drm_modeset_lock(&plane->mutex, ctx);
if (ret)
return ret;
}
return 0;
}
EXPORT_SYMBOL(drm_modeset_lock_all_ctx);