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The current code for bridge address events has two shortcomings in its control sequence: 1. after disabling address events via PNSO, we don't flush the remaining events from the event_wq. So if the feature is re-enabled fast enough, stale events could leak over. 2. PNSO and the events' arrival via the READ ccw device are unordered. So even if we flushed the workqueue, it's difficult to say whether the READ device might produce more events onto the workqueue afterwards. Fix this by 1. explicitly fencing off the events when we no longer care, in the READ device's event handler. This ensures that once we flush the workqueue, it doesn't get additional address events. 2. Flush the workqueue after disabling the events & fencing them off. As the code that triggers the flush will typically hold the sbp_lock, we need to rework the worker code to avoid a deadlock here in case of a 'notifications-stopped' event. In case of lock contention, requeue such an event with a delay. We'll eventually aquire the lock, or spot that the feature has been disabled and the event can thus be discarded. This leaves the theoretical race that a stale event could arrive _after_ we re-enabled ourselves to receive events again. Such an event would be impossible to distinguish from a 'good' event, nothing we can do about it. Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com> Reviewed-by: Alexandra Winter <wintera@linux.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.