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ib_crate_cm_id() immediately places the id in the xarray, and publishes it into the remote_id and remote_qpn rbtrees. This makes it visible to other threads before it is fully set up. It appears the thinking here was that the states IB_CM_IDLE and IB_CM_REQ_RCVD do not allow any MAD handler or lookup in the remote_id and remote_qpn rbtrees to advance. However, cm_rej_handler() does take an action on IB_CM_REQ_RCVD, which is not really expected by the design. Make the whole thing clearer: - Keep the new cm_id out of the xarray until it is completely set up. This directly prevents MAD handlers and all rbtree lookups from seeing the pointer. - Move all the trivial setup right to the top so it is obviously done before any concurrency begins - Move the mutation of the cm_id_priv out of cm_match_id() and into the caller so the state transition is obvious - Place the manipulation of the work_list at the end, under lock, after the cm_id is placed in the xarray. The work_count cannot change on an ID outside the xarray. - Add some comments Link: https://lore.kernel.org/r/20200310092545.251365-9-leon@kernel.org Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
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.