b1e3177bd1
Forgo the struct_mutex serialisation for i915_active, and interpose its own mutex handling for active/retire. This is a multi-layered sleight-of-hand. First, we had to ensure that no active/retire callbacks accidentally inverted the mutex ordering rules, nor assumed that they were themselves serialised by struct_mutex. More challenging though, is the rule over updating elements of the active rbtree. Instead of the whole i915_active now being serialised by struct_mutex, allocations/rotations of the tree are serialised by the i915_active.mutex and individual nodes are serialised by the caller using the i915_timeline.mutex (we need to use nested spinlocks to interact with the dma_fence callback lists). The pain point here is that instead of a single mutex around execbuf, we now have to take a mutex for active tracker (one for each vma, context, etc) and a couple of spinlocks for each fence update. The improvement in fine grained locking allowing for multiple concurrent clients (eventually!) should be worth it in typical loads. v2: Add some comments that barely elucidate anything :( Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191004134015.13204-6-chris@chris-wilson.co.uk
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.