mirror of
https://github.com/torvalds/linux.git
synced 2026-07-29 02:31:27 +02:00
Linux kernel source tree
a4c1cdd34e
The current context uAPI allows for two methods of setting context parameters: SET_CONTEXT_PARAM and CONTEXT_CREATE_EXT_SETPARAM. The former is allowed to be called at any time while the later happens as part of GEM_CONTEXT_CREATE. Currently, everything settable via one is settable via the other. While some params are fairly simple and setting them on a live context is harmless such as the context priority, others are far trickier such as the VM or the set of engines. In order to swap out the VM, for instance, we have to delay until all current in-flight work is complete, swap in the new VM, and then continue. This leads to a plethora of potential race conditions we'd really rather avoid. In previous patches, we added a i915_gem_proto_context struct which is capable of storing and tracking all such create parameters. This commit delays the creation of the actual context until after the client is done configuring it with SET_CONTEXT_PARAM. From the perspective of the client, it has the same u32 context ID the whole time. From the perspective of i915, however, it's an i915_gem_proto_context right up until the point where we attempt to do something which the proto-context can't handle. Then the real context gets created. This is accomplished via a little xarray dance. When GEM_CONTEXT_CREATE is called, we create a proto-context, reserve a slot in context_xa but leave it NULL, the proto-context in the corresponding slot in proto_context_xa. Then, whenever we go to look up a context, we first check context_xa. If it's there, we return the i915_gem_context and we're done. If it's not, we look in proto_context_xa and, if we find it there, we create the actual context and kill the proto-context. In order for this dance to work properly, everything which ever touches a proto-context is guarded by drm_i915_file_private::proto_context_lock, including context creation. Yes, this means context creation now takes a giant global lock but it can't really be helped and that should never be on any driver's fast-path anyway. v2 (Daniel Vetter): - Commit message grammatical fixes. - Use WARN_ON instead of GEM_BUG_ON - Rename lazy_create_context_locked to finalize_create_context_locked - Rework the control-flow logic in the setparam ioctl - Better documentation all around v3 (kernel test robot): - Make finalize_create_context_locked static Signed-off-by: Jason Ekstrand <jason@jlekstrand.net> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20210708154835.528166-25-jason@jlekstrand.net |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.