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To support queue mapped to a CPU, it needs to be ensured that issuing an internal abort is safe, in that it is guaranteed that an internal abort is processed for a single IO or a device after all the relevant command(s) which it is attempting to abort have been processed by the controller. Currently we only deliver commands for any device on a single queue to solve this problem, as we know that commands issued on the same queue will be processed in order, and we will not have a scenario where the internal abort is racing against a command(s) which it is trying to abort. To enqueue commands on queue mapped to a CPU, choosing a queue for an command is based on the associated queue for the current CPU, so this is not safe for internal abort since it would definitely not be guaranteed that commands for the command devices are issued on the same queue. To solve this issue, we take a bludgeoning approach, and issue a separate internal abort on any queue(s) relevant to the command or device, in that we will be guaranteed that at least one of these internal aborts will be received last in the controller. So, for aborting a single command, we can just force the internal abort to be issued on the same queue as the command which we are trying to abort. For aborting all commands associated with a device, we issue a separate internal abort on all relevant queues. Issuing multiple internal aborts in this fashion would have not side affect. Signed-off-by: John Garry <john.garry@huawei.com> Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
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| README | ||
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.