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![Linus Torvalds](/assets/img/avatar_default.png)
-----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE+QmuaPwR3wnBdVwACF8+vY7k4RUFAl0tpocACgkQCF8+vY7k 4RWoxA//b/fmDXP3WPzrjjSmpyB9ml0/epKzPbT5S2j0lftqKBmet29k+PCjVrTx Nq2QauehY9ug5h8UMVUCmzPr95F0tSIGRoqk1vrn7z0K3q6k1SHrtvqbY1Bgb2Uk Qvh2YFU4fQLJg8WAbExCjxCdbdmBKQVGKTwCtM+tP5OMxwAFOmQrjGaUaKCKIIA2 7Wzrx8CpSji+bJ3uK/d36c+4M9oDly5eaxBhoboL3BI0y+GqwiSASGwTO7BxrPOg 0wq5IZHnqS8+bprT9xQdDOqf+UOY9U1cxE/+sqsHxblfUEx9gfLy/R+FLmJn+SS9 Z3yLy4SqVHQMpWBjEAGodohikF60PAuTdymSC11jqFaKCUxWrIZg5xO+0blMrxPF 7vYIexutCkaBMHBlNaNsHIqB7B/2FGGKoN7QW64hwvwJCGvF7OmJcV+R4bROGvh4 nFuis9/Nm66Fq7I3aw37ThyZ0aWZdaQ0QJTH9ksxU/ZCz2hhMNYu/rXggrDvkS4U nr77ZT5Gd7nj4b110zf8+99uiGiinY6hTfzPAuTCLBhaxwrv4/xDHAhpwdEB5T4j 8gOkxV8c0XWtL7sKqhGJvs/RRe2za0Y9XH6fyxsYfWcfuLjEvug8ouXMad9gxFWH DL3WnKJEMGLScei2wux4kGOwEbkR1bUf2cHJfh3GpCB/y8vgLOc= =smxY -----END PGP SIGNATURE----- Merge tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media Pull rst conversion of docs from Mauro Carvalho Chehab: "As agreed with Jon, I'm sending this big series directly to you, c/c him, as this series required a special care, in order to avoid conflicts with other trees" * tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (77 commits) docs: kbuild: fix build with pdf and fix some minor issues docs: block: fix pdf output docs: arm: fix a breakage with pdf output docs: don't use nested tables docs: gpio: add sysfs interface to the admin-guide docs: locking: add it to the main index docs: add some directories to the main documentation index docs: add SPDX tags to new index files docs: add a memory-devices subdir to driver-api docs: phy: place documentation under driver-api docs: serial: move it to the driver-api docs: driver-api: add remaining converted dirs to it docs: driver-api: add xilinx driver API documentation docs: driver-api: add a series of orphaned documents docs: admin-guide: add a series of orphaned documents docs: cgroup-v1: add it to the admin-guide book docs: aoe: add it to the driver-api book docs: add some documentation dirs to the driver-api book docs: driver-model: move it to the driver-api book docs: lp855x-driver.rst: add it to the driver-api book ...
427 lines
12 KiB
C
427 lines
12 KiB
C
/*
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* Copyright (C) 2014 Red Hat
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* Author: Rob Clark <robdclark@gmail.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <drm/drm_atomic.h>
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#include <drm/drm_crtc.h>
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#include <drm/drm_device.h>
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#include <drm/drm_modeset_lock.h>
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/**
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* DOC: kms locking
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*
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* As KMS moves toward more fine grained locking, and atomic ioctl where
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* userspace can indirectly control locking order, it becomes necessary
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* to use &ww_mutex and acquire-contexts to avoid deadlocks. But because
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* the locking is more distributed around the driver code, we want a bit
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* of extra utility/tracking out of our acquire-ctx. This is provided
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* by &struct drm_modeset_lock and &struct drm_modeset_acquire_ctx.
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*
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* For basic principles of &ww_mutex, see: Documentation/locking/ww-mutex-design.rst
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*
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* The basic usage pattern is to::
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*
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* drm_modeset_acquire_init(ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
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* retry:
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* foreach (lock in random_ordered_set_of_locks) {
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* ret = drm_modeset_lock(lock, ctx)
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* if (ret == -EDEADLK) {
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* ret = drm_modeset_backoff(ctx);
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* if (!ret)
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* goto retry;
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* }
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* if (ret)
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* goto out;
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* }
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* ... do stuff ...
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* out:
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* drm_modeset_drop_locks(ctx);
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* drm_modeset_acquire_fini(ctx);
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*
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* For convenience this control flow is implemented in
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* DRM_MODESET_LOCK_ALL_BEGIN() and DRM_MODESET_LOCK_ALL_END() for the case
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* where all modeset locks need to be taken through drm_modeset_lock_all_ctx().
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*
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* If all that is needed is a single modeset lock, then the &struct
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* drm_modeset_acquire_ctx is not needed and the locking can be simplified
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* by passing a NULL instead of ctx in the drm_modeset_lock() call or
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* calling drm_modeset_lock_single_interruptible(). To unlock afterwards
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* call drm_modeset_unlock().
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*
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* On top of these per-object locks using &ww_mutex there's also an overall
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* &drm_mode_config.mutex, for protecting everything else. Mostly this means
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* probe state of connectors, and preventing hotplug add/removal of connectors.
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*
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* Finally there's a bunch of dedicated locks to protect drm core internal
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* lists and lookup data structures.
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*/
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static DEFINE_WW_CLASS(crtc_ww_class);
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/**
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* drm_modeset_lock_all - take all modeset locks
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* @dev: DRM device
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*
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* This function takes all modeset locks, suitable where a more fine-grained
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* scheme isn't (yet) implemented. Locks must be dropped by calling the
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* drm_modeset_unlock_all() function.
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*
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* This function is deprecated. It allocates a lock acquisition context and
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* stores it in &drm_device.mode_config. This facilitate conversion of
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* existing code because it removes the need to manually deal with the
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* acquisition context, but it is also brittle because the context is global
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* and care must be taken not to nest calls. New code should use the
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* drm_modeset_lock_all_ctx() function and pass in the context explicitly.
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*/
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void drm_modeset_lock_all(struct drm_device *dev)
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{
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struct drm_mode_config *config = &dev->mode_config;
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struct drm_modeset_acquire_ctx *ctx;
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int ret;
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ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
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if (WARN_ON(!ctx))
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return;
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mutex_lock(&config->mutex);
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drm_modeset_acquire_init(ctx, 0);
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retry:
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ret = drm_modeset_lock_all_ctx(dev, ctx);
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if (ret < 0) {
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if (ret == -EDEADLK) {
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drm_modeset_backoff(ctx);
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goto retry;
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}
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drm_modeset_acquire_fini(ctx);
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kfree(ctx);
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return;
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}
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ww_acquire_done(&ctx->ww_ctx);
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WARN_ON(config->acquire_ctx);
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/*
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* We hold the locks now, so it is safe to stash the acquisition
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* context for drm_modeset_unlock_all().
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*/
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config->acquire_ctx = ctx;
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drm_warn_on_modeset_not_all_locked(dev);
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}
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EXPORT_SYMBOL(drm_modeset_lock_all);
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/**
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* drm_modeset_unlock_all - drop all modeset locks
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* @dev: DRM device
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*
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* This function drops all modeset locks taken by a previous call to the
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* drm_modeset_lock_all() function.
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*
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* This function is deprecated. It uses the lock acquisition context stored
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* in &drm_device.mode_config. This facilitates conversion of existing
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* code because it removes the need to manually deal with the acquisition
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* context, but it is also brittle because the context is global and care must
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* be taken not to nest calls. New code should pass the acquisition context
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* directly to the drm_modeset_drop_locks() function.
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*/
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void drm_modeset_unlock_all(struct drm_device *dev)
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{
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struct drm_mode_config *config = &dev->mode_config;
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struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;
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if (WARN_ON(!ctx))
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return;
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config->acquire_ctx = NULL;
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drm_modeset_drop_locks(ctx);
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drm_modeset_acquire_fini(ctx);
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kfree(ctx);
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mutex_unlock(&dev->mode_config.mutex);
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}
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EXPORT_SYMBOL(drm_modeset_unlock_all);
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/**
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* drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
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* @dev: device
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*
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* Useful as a debug assert.
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*/
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void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
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{
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struct drm_crtc *crtc;
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/* Locking is currently fubar in the panic handler. */
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if (oops_in_progress)
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return;
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drm_for_each_crtc(crtc, dev)
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WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
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WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
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WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
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}
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EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
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/**
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* drm_modeset_acquire_init - initialize acquire context
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* @ctx: the acquire context
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* @flags: 0 or %DRM_MODESET_ACQUIRE_INTERRUPTIBLE
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*
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* When passing %DRM_MODESET_ACQUIRE_INTERRUPTIBLE to @flags,
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* all calls to drm_modeset_lock() will perform an interruptible
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* wait.
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*/
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void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
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uint32_t flags)
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{
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memset(ctx, 0, sizeof(*ctx));
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ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
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INIT_LIST_HEAD(&ctx->locked);
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if (flags & DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
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ctx->interruptible = true;
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}
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EXPORT_SYMBOL(drm_modeset_acquire_init);
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/**
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* drm_modeset_acquire_fini - cleanup acquire context
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* @ctx: the acquire context
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*/
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void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
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{
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ww_acquire_fini(&ctx->ww_ctx);
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}
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EXPORT_SYMBOL(drm_modeset_acquire_fini);
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/**
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* drm_modeset_drop_locks - drop all locks
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* @ctx: the acquire context
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*
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* Drop all locks currently held against this acquire context.
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*/
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void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx)
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{
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WARN_ON(ctx->contended);
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while (!list_empty(&ctx->locked)) {
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struct drm_modeset_lock *lock;
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lock = list_first_entry(&ctx->locked,
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struct drm_modeset_lock, head);
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drm_modeset_unlock(lock);
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}
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}
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EXPORT_SYMBOL(drm_modeset_drop_locks);
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static inline int modeset_lock(struct drm_modeset_lock *lock,
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struct drm_modeset_acquire_ctx *ctx,
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bool interruptible, bool slow)
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{
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int ret;
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WARN_ON(ctx->contended);
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if (ctx->trylock_only) {
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lockdep_assert_held(&ctx->ww_ctx);
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if (!ww_mutex_trylock(&lock->mutex))
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return -EBUSY;
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else
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return 0;
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} else if (interruptible && slow) {
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ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);
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} else if (interruptible) {
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ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);
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} else if (slow) {
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ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);
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ret = 0;
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} else {
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ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);
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}
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if (!ret) {
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WARN_ON(!list_empty(&lock->head));
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list_add(&lock->head, &ctx->locked);
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} else if (ret == -EALREADY) {
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/* we already hold the lock.. this is fine. For atomic
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* we will need to be able to drm_modeset_lock() things
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* without having to keep track of what is already locked
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* or not.
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*/
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ret = 0;
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} else if (ret == -EDEADLK) {
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ctx->contended = lock;
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}
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return ret;
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}
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/**
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* drm_modeset_backoff - deadlock avoidance backoff
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* @ctx: the acquire context
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*
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* If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
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* you must call this function to drop all currently held locks and
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* block until the contended lock becomes available.
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*
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* This function returns 0 on success, or -ERESTARTSYS if this context
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* is initialized with %DRM_MODESET_ACQUIRE_INTERRUPTIBLE and the
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* wait has been interrupted.
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*/
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int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
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{
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struct drm_modeset_lock *contended = ctx->contended;
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ctx->contended = NULL;
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if (WARN_ON(!contended))
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return 0;
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drm_modeset_drop_locks(ctx);
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return modeset_lock(contended, ctx, ctx->interruptible, true);
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}
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EXPORT_SYMBOL(drm_modeset_backoff);
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/**
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* drm_modeset_lock_init - initialize lock
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* @lock: lock to init
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*/
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void drm_modeset_lock_init(struct drm_modeset_lock *lock)
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{
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ww_mutex_init(&lock->mutex, &crtc_ww_class);
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INIT_LIST_HEAD(&lock->head);
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}
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EXPORT_SYMBOL(drm_modeset_lock_init);
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/**
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* drm_modeset_lock - take modeset lock
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* @lock: lock to take
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* @ctx: acquire ctx
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*
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* If @ctx is not NULL, then its ww acquire context is used and the
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* lock will be tracked by the context and can be released by calling
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* drm_modeset_drop_locks(). If -EDEADLK is returned, this means a
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* deadlock scenario has been detected and it is an error to attempt
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* to take any more locks without first calling drm_modeset_backoff().
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*
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* If the @ctx is not NULL and initialized with
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* %DRM_MODESET_ACQUIRE_INTERRUPTIBLE, this function will fail with
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* -ERESTARTSYS when interrupted.
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*
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* If @ctx is NULL then the function call behaves like a normal,
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* uninterruptible non-nesting mutex_lock() call.
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*/
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int drm_modeset_lock(struct drm_modeset_lock *lock,
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struct drm_modeset_acquire_ctx *ctx)
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{
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if (ctx)
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return modeset_lock(lock, ctx, ctx->interruptible, false);
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ww_mutex_lock(&lock->mutex, NULL);
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return 0;
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}
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EXPORT_SYMBOL(drm_modeset_lock);
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/**
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* drm_modeset_lock_single_interruptible - take a single modeset lock
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* @lock: lock to take
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*
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* This function behaves as drm_modeset_lock() with a NULL context,
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* but performs interruptible waits.
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*
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* This function returns 0 on success, or -ERESTARTSYS when interrupted.
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*/
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int drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock)
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{
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return ww_mutex_lock_interruptible(&lock->mutex, NULL);
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}
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EXPORT_SYMBOL(drm_modeset_lock_single_interruptible);
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/**
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* drm_modeset_unlock - drop modeset lock
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* @lock: lock to release
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*/
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void drm_modeset_unlock(struct drm_modeset_lock *lock)
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{
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list_del_init(&lock->head);
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ww_mutex_unlock(&lock->mutex);
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}
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EXPORT_SYMBOL(drm_modeset_unlock);
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/**
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* drm_modeset_lock_all_ctx - take all modeset locks
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* @dev: DRM device
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* @ctx: lock acquisition context
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*
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* This function takes all modeset locks, suitable where a more fine-grained
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* scheme isn't (yet) implemented.
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*
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* Unlike drm_modeset_lock_all(), it doesn't take the &drm_mode_config.mutex
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* since that lock isn't required for modeset state changes. Callers which
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* need to grab that lock too need to do so outside of the acquire context
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* @ctx.
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*
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* Locks acquired with this function should be released by calling the
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* drm_modeset_drop_locks() function on @ctx.
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*
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* See also: DRM_MODESET_LOCK_ALL_BEGIN() and DRM_MODESET_LOCK_ALL_END()
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*
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* Returns: 0 on success or a negative error-code on failure.
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*/
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int drm_modeset_lock_all_ctx(struct drm_device *dev,
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struct drm_modeset_acquire_ctx *ctx)
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{
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struct drm_private_obj *privobj;
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struct drm_crtc *crtc;
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struct drm_plane *plane;
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int ret;
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ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
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if (ret)
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return ret;
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drm_for_each_crtc(crtc, dev) {
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ret = drm_modeset_lock(&crtc->mutex, ctx);
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if (ret)
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return ret;
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}
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drm_for_each_plane(plane, dev) {
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ret = drm_modeset_lock(&plane->mutex, ctx);
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if (ret)
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return ret;
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}
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drm_for_each_privobj(privobj, dev) {
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ret = drm_modeset_lock(&privobj->lock, ctx);
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if (ret)
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return ret;
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}
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return 0;
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}
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EXPORT_SYMBOL(drm_modeset_lock_all_ctx);
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