735dc0d1e2
The aim of this locking rework is that ioctls which a compositor should be might call for every frame (set_cursor, page_flip, addfb, rmfb and getfb/create_handle) should not be able to block on kms background activities like output detection. And since each EDID read takes about 25ms (in the best case), that always means we'll drop at least one frame. The solution is to add per-crtc locking for these ioctls, and restrict background activities to only use the global lock. Change-the-world type of events (modeset, dpms, ...) need to grab all locks. Two tricky parts arose in the conversion: - A lot of current code assumes that a kms fb object can't disappear while holding the global lock, since the current code serializes fb destruction with it. Hence proper lifetime management using the already created refcounting for fbs need to be instantiated for all ioctls and interfaces/users. - The rmfb ioctl removes the to-be-deleted fb from all active users. But unconditionally taking the global kms lock to do so introduces an unacceptable potential stall point. And obviously changing the userspace abi isn't on the table, either. Hence this conversion opportunistically checks whether the rmfb ioctl holds the very last reference, which guarantees that the fb isn't in active use on any crtc or plane (thanks to the conversion to the new lifetime rules using proper refcounting). Only if this is not the case will the code go through the slowpath and grab all modeset locks. Sane compositors will never hit this path and so avoid the stall, but userspace relying on these semantics will also not break. All these cases are exercised by the newly added subtests for the i-g-t kms_flip, tested on a machine where a full detect cycle takes around 100 ms. It works, and no frames are dropped any more with these patches applied. kms_flip also contains a special case to exercise the above-describe rmfb slowpath. * 'drm-kms-locking' of git://people.freedesktop.org/~danvet/drm-intel: (335 commits) drm/fb_helper: check whether fbcon is bound drm/doc: updates for new framebuffer lifetime rules drm: don't hold crtc mutexes for connector ->detect callbacks drm: only grab the crtc lock for pageflips drm: optimize drm_framebuffer_remove drm/vmwgfx: add proper framebuffer refcounting drm/i915: dump refcount into framebuffer debugfs file drm: refcounting for crtc framebuffers drm: refcounting for sprite framebuffers drm: fb refcounting for dirtyfb_ioctl drm: don't take modeset locks in getfb ioctl drm: push modeset_lock_all into ->fb_create driver callbacks drm: nest modeset locks within fpriv->fbs_lock drm: reference framebuffers which are on the idr drm: revamp framebuffer cleanup interfaces drm: create drm_framebuffer_lookup drm: revamp locking around fb creation/destruction drm: only take the crtc lock for ->cursor_move drm: only take the crtc lock for ->cursor_set drm: add per-crtc locks ... |
||
|---|---|---|
| .. | ||
| ast | ||
| cirrus | ||
| exynos | ||
| gma500 | ||
| i2c | ||
| i810 | ||
| i915 | ||
| mga | ||
| mgag200 | ||
| nouveau | ||
| r128 | ||
| radeon | ||
| savage | ||
| shmobile | ||
| sis | ||
| tdfx | ||
| tegra | ||
| 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.c | ||
| drm_debugfs.c | ||
| drm_dma.c | ||
| drm_dp_helper.c | ||
| drm_drv.c | ||
| drm_edid_load.c | ||
| drm_edid_modes.h | ||
| drm_edid.c | ||
| drm_encoder_slave.c | ||
| drm_fb_cma_helper.c | ||
| drm_fb_helper.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_mm.c | ||
| drm_modes.c | ||
| drm_pci.c | ||
| drm_platform.c | ||
| drm_prime.c | ||
| drm_proc.c | ||
| drm_scatter.c | ||
| drm_stub.c | ||
| drm_sysfs.c | ||
| drm_trace_points.c | ||
| drm_trace.h | ||
| drm_usb.c | ||
| drm_vm.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