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There used to be a rcu_barrier() for SLAB_TYPESAFE_BY_RCU caches in kmem_cache_destroy() until commit657dc2f972("slab: remove synchronous rcu_barrier() call in memcg cache release path") moved it to an asynchronous work that finishes the destroying of such caches. The motivation for that commit was the MEMCG_KMEM integration that at the time created and removed clones of the global slab caches together with their cgroups, and blocking cgroups removal was unwelcome. The implementation later changed to per-object memcg tracking using a single cache, so there should be no more need for a fast non-blocking kmem_cache_destroy(), which is typically only done when a module is unloaded etc. Going back to synchronous barrier has the following advantages: - simpler implementation - it's easier to test the result of kmem_cache_destroy() in a kunit test Thus effectively revert commit657dc2f972. It is not a 1:1 revert as the code has changed since. The main part is that kmem_cache_release(s) is always called from kmem_cache_destroy(), but for SLAB_TYPESAFE_BY_RCU caches there's a rcu_barrier() first. Suggested-by: Mateusz Guzik <mjguzik@gmail.com> Reviewed-by: Jann Horn <jannh@google.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
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 reStructuredText 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.