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Allocate agent IDs from a global IDR instead of an atomic variable. This eliminates the possibility of reusing an ID which is already in use after 4 billion registrations. We limit the assigned ID to be less than 2^24 as the mlx4 driver uses the most significant byte of the agent ID to store the slave number. Users unlucky enough to see a collision between agent numbers and slave numbers see messages like: mlx4_ib: egress mad has non-null tid msb:1 class:4 slave:0 and the MAD layer stops working. We look up the agent under protection of the RCU lock, which means we have to free the agent using kfree_rcu, and only increment the reference counter if it is not 0. Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Reported-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com> Acked-by: Jack Morgenstein <jackm@dev.mellanox.co.il> Tested-by: Jack Morgenstein <jackm@dev.mellanox.co.il> 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
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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.
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.