linux-stable/drivers/gpu/drm/drm_modeset_lock.c
Daniel Vetter 4d02e2de0e drm: Per-plane locking
Turned out to be much simpler on top of my latest atomic stuff than
what I've feared. Some details:

- Drop the modeset_lock_all snakeoil in drm_plane_init. Same
  justification as for the equivalent change in drm_crtc_init done in

	commit d0fa1af40e
	Author: Daniel Vetter <daniel.vetter@ffwll.ch>
	Date:   Mon Sep 8 09:02:49 2014 +0200

	    drm: Drop modeset locking from crtc init function

  Without these the drm_modeset_lock_init would fall over the exact
  same way.

- Since the atomic core code wraps the locking switching it to
  per-plane locks was a one-line change.

- For the legacy ioctls add a plane argument to the locking helper so
  that we can grab the right plane lock (cursor or primary). Since the
  universal cursor plane might not be there, or someone really crazy
  might forgoe the primary plane even accept NULL.

- Add some locking WARN_ON to the atomic helpers for good paranoid
  measure and to check that it all works out.

Tested on my exynos atomic hackfest with full lockdep checks and ww
backoff injection.

v2: I've forgotten about the load-detect code in i915.

v3: Thierry reported that in latest 3.18-rc vmwgfx doesn't compile any
more due to

commit 21e88620aa
Author: Rob Clark <robdclark@gmail.com>
Date:   Thu Oct 30 13:39:04 2014 -0400

    drm/vmwgfx: fix lock breakage

Rebased and fix this up.

Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
2014-11-12 17:56:12 +10:00

482 lines
12 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 drm_modeset_lock / 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);
*/
/**
* __drm_modeset_lock_all - internal helper to grab all modeset locks
* @dev: DRM device
* @trylock: trylock mode for atomic contexts
*
* This is a special version of drm_modeset_lock_all() which can also be used in
* atomic contexts. Then @trylock must be set to true.
*
* Returns:
* 0 on success or negative error code on failure.
*/
int __drm_modeset_lock_all(struct drm_device *dev,
bool trylock)
{
struct drm_mode_config *config = &dev->mode_config;
struct drm_modeset_acquire_ctx *ctx;
int ret;
ctx = kzalloc(sizeof(*ctx),
trylock ? GFP_ATOMIC : GFP_KERNEL);
if (!ctx)
return -ENOMEM;
if (trylock) {
if (!mutex_trylock(&config->mutex))
return -EBUSY;
} else {
mutex_lock(&config->mutex);
}
drm_modeset_acquire_init(ctx, 0);
ctx->trylock_only = trylock;
retry:
ret = drm_modeset_lock(&config->connection_mutex, ctx);
if (ret)
goto fail;
ret = drm_modeset_lock_all_crtcs(dev, ctx);
if (ret)
goto fail;
WARN_ON(config->acquire_ctx);
/* now we hold the locks, so now that it is safe, stash the
* ctx for drm_modeset_unlock_all():
*/
config->acquire_ctx = ctx;
drm_warn_on_modeset_not_all_locked(dev);
return 0;
fail:
if (ret == -EDEADLK) {
drm_modeset_backoff(ctx);
goto retry;
}
return ret;
}
EXPORT_SYMBOL(__drm_modeset_lock_all);
/**
* 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 with
* drm_modeset_unlock_all.
*/
void drm_modeset_lock_all(struct drm_device *dev)
{
WARN_ON(__drm_modeset_lock_all(dev, false) != 0);
}
EXPORT_SYMBOL(drm_modeset_lock_all);
/**
* drm_modeset_unlock_all - drop all modeset locks
* @dev: device
*
* This function drop all modeset locks taken by drm_modeset_lock_all.
*/
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_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update
* @crtc: DRM CRTC
* @plane: DRM plane to be updated on @crtc
*
* This function locks the given crtc and plane (which should be either the
* primary or cursor plane) using a hidden acquire context. This is necessary so
* that drivers internally using the atomic interfaces can grab further locks
* with the lock acquire context.
*
* Note that @plane can be NULL, e.g. when the cursor support hasn't yet been
* converted to universal planes yet.
*/
void drm_modeset_lock_crtc(struct drm_crtc *crtc,
struct drm_plane *plane)
{
struct drm_modeset_acquire_ctx *ctx;
int ret;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (WARN_ON(!ctx))
return;
drm_modeset_acquire_init(ctx, 0);
retry:
ret = drm_modeset_lock(&crtc->mutex, ctx);
if (ret)
goto fail;
if (plane) {
ret = drm_modeset_lock(&plane->mutex, ctx);
if (ret)
goto fail;
if (plane->crtc) {
ret = drm_modeset_lock(&plane->crtc->mutex, ctx);
if (ret)
goto fail;
}
}
WARN_ON(crtc->acquire_ctx);
/* now we hold the locks, so now that it is safe, stash the
* ctx for drm_modeset_unlock_crtc():
*/
crtc->acquire_ctx = ctx;
return;
fail:
if (ret == -EDEADLK) {
drm_modeset_backoff(ctx);
goto retry;
}
}
EXPORT_SYMBOL(drm_modeset_lock_crtc);
/**
* drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls
* @crtc: drm crtc
*
* Legacy ioctl operations like cursor updates or page flips only have per-crtc
* locking, and store the acquire ctx in the corresponding crtc. All other
* legacy operations take all locks and use a global acquire context. This
* function grabs the right one.
*/
struct drm_modeset_acquire_ctx *
drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc)
{
if (crtc->acquire_ctx)
return crtc->acquire_ctx;
WARN_ON(!crtc->dev->mode_config.acquire_ctx);
return crtc->dev->mode_config.acquire_ctx;
}
EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx);
/**
* drm_modeset_unlock_crtc - drop crtc lock
* @crtc: drm crtc
*
* This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other
* locks acquired through the hidden context.
*/
void drm_modeset_unlock_crtc(struct drm_crtc *crtc)
{
struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx;
if (WARN_ON(!ctx))
return;
crtc->acquire_ctx = NULL;
drm_modeset_drop_locks(ctx);
drm_modeset_acquire_fini(ctx);
kfree(ctx);
}
EXPORT_SYMBOL(drm_modeset_unlock_crtc);
/**
* 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;
list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
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) {
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 - 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);
/* In some legacy codepaths it's convenient to just grab all the crtc and plane
* related locks. */
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;
struct drm_plane *plane;
int ret = 0;
list_for_each_entry(crtc, &config->crtc_list, head) {
ret = drm_modeset_lock(&crtc->mutex, ctx);
if (ret)
return ret;
}
list_for_each_entry(plane, &config->plane_list, head) {
ret = drm_modeset_lock(&plane->mutex, ctx);
if (ret)
return ret;
}
return 0;
}
EXPORT_SYMBOL(drm_modeset_lock_all_crtcs);