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The synchronize_rcu() call can be eliminated to improve memory deregistration performance. There are two key fields involved: - The rcu pointer itself - the lkey_published field To close the window between the rcu read of the mregion pointer and the reference count the code should: 1. To lkey/rkey validation (reader) Read the rcu pointer. If the pointer is non-NULL, get a reference. To the current validation tests use a READ_ONCE() on the lkey_published. Upon any failure release the reference. 2. To the remove logic (delete) Insure the published is zeroed prior to setting the pointer to NULL. This requires using rcu_assign_pointer() to insure lkey_published is written prior to the NULL. 3. To the insert logic (add) Insure the published is set use an rcu_assign_pointer() to insure the pointer is after all MR fields. Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com> Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.