6e9f798d91
After the split-out of crtc locks from the big mode_config.mutex there's still two major areas it protects: - Various connector probe states, like connector->status, EDID properties, probed mode lists and similar information. - The links from connector->encoder and encoder->crtc and other modeset-relevant connector state (e.g. properties which control the panel fitter). The later is used by modeset operations. But they don't really care about the former since it's allowed to e.g. enable a disconnected VGA output or with a mode not in the probed list. Thus far this hasn't been a problem, but for the atomic modeset conversion Rob Clark needs to convert all modeset relevant locks into w/w locks. This is required because the order of acquisition is determined by how userspace supplies the atomic modeset data. This has run into troubles in the detect path since the i915 load detect code needs _both_ protections offered by the mode_config.mutex: It updates probe state and it needs to change the modeset configuration to enable the temporary load detect pipe. The big deal here is that for the probe/detect users of this lock a plain mutex fits best, but for atomic modesets we really want a w/w mutex. To fix this lets split out a new connection_mutex lock for the modeset relevant parts. For simplicity I've decided to only add one additional lock for all connector/encoder links and modeset configuration states. We have piles of different modeset objects in addition to those (like bridges or panels), so adding per-object locks would be much more effort. Also, we're guaranteed (at least for now) to do a full modeset if we need to acquire this lock. Which means that fine-grained locking is fairly irrelevant compared to the amount of time the full modeset will take. I've done a full audit, and there's just a few things that justify special focus: - Locking in drm_sysfs.c is almost completely absent. We should sprinkle mode_config.connection_mutex over this file a bit, but since it already lacks mode_config.mutex this patch wont make the situation any worse. This is material for a follow-up patch. - omap has a omap_framebuffer_flush function which walks the connector->encoder->crtc links and is called from many contexts. Some look like they don't acquire mode_config.mutex, so this is already racy. Again fixing this is material for a separate patch. - The radeon hot_plug function to retrain DP links looks at connector->dpms. Currently this happens without any locking, so is already racy. I think radeon_hotplug_work_func should gain mutex_lock/unlock calls for the mode_config.connection_mutex. - Same applies to i915's intel_dp_hot_plug. But again, this is already racy. - i915 load_detect code needs to acquire this lock. Which means the w/w dance due to Rob's work will be nicely contained to _just_ this function. I've added fixme comments everywhere where it looks suspicious but in the sysfs code. After a quick irc discussion with Dave Airlie it sounds like the lack of locking in there is due to sysfs cleanup fun at module unload. v1: original (only compile tested) v2: missing mutex_init(), etc (from Rob Clark) v3: i915 needs more care in the conversion: - Protect the edp pp logic with the connection_mutex. - Use connection_mutex in the backlight code due to get_pipe_from_connector. - Use drm_modeset_lock_all in suspend/resume paths. - Update lock checks in the overlay code. Cc: Alex Deucher <alexdeucher@gmail.com> Cc: Rob Clark <robdclark@gmail.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Reviewed-by: Rob Clark <robdclark@gmail.com> |
||
|---|---|---|
| .. | ||
| armada | ||
| ast | ||
| bochs | ||
| bridge | ||
| cirrus | ||
| exynos | ||
| gma500 | ||
| i2c | ||
| i810 | ||
| i915 | ||
| mga | ||
| mgag200 | ||
| msm | ||
| nouveau | ||
| omapdrm | ||
| panel | ||
| qxl | ||
| r128 | ||
| radeon | ||
| rcar-du | ||
| savage | ||
| shmobile | ||
| sis | ||
| tdfx | ||
| tegra | ||
| tilcdc | ||
| ttm | ||
| udl | ||
| via | ||
| vmwgfx | ||
| ati_pcigart.c | ||
| drm_agpsupport.c | ||
| drm_auth.c | ||
| drm_buffer.c | ||
| drm_bufs.c | ||
| drm_cache.c | ||
| drm_context.c | ||
| drm_crtc_helper.c | ||
| drm_crtc_internal.h | ||
| drm_crtc.c | ||
| drm_debugfs.c | ||
| drm_dma.c | ||
| drm_dp_helper.c | ||
| drm_drv.c | ||
| drm_edid_load.c | ||
| drm_edid.c | ||
| drm_encoder_slave.c | ||
| drm_fb_cma_helper.c | ||
| drm_fb_helper.c | ||
| drm_flip_work.c | ||
| drm_fops.c | ||
| drm_gem_cma_helper.c | ||
| drm_gem.c | ||
| drm_global.c | ||
| drm_hashtab.c | ||
| drm_info.c | ||
| drm_ioc32.c | ||
| drm_ioctl.c | ||
| drm_irq.c | ||
| drm_lock.c | ||
| drm_memory.c | ||
| drm_mipi_dsi.c | ||
| drm_mm.c | ||
| drm_modes.c | ||
| drm_panel.c | ||
| drm_pci.c | ||
| drm_plane_helper.c | ||
| drm_platform.c | ||
| drm_prime.c | ||
| drm_probe_helper.c | ||
| drm_rect.c | ||
| drm_scatter.c | ||
| drm_stub.c | ||
| drm_sysfs.c | ||
| drm_trace_points.c | ||
| drm_trace.h | ||
| drm_usb.c | ||
| drm_vm.c | ||
| drm_vma_manager.c | ||
| Kconfig | ||
| Makefile | ||
| README.drm | ||
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html