Marco Elver
c862f6124f
To toggle the allocation gates, we set up a delayed work that calls toggle_allocation_gate(). Here we use wait_event() to await an allocation and subsequently disable the static branch again. However, if the kernel has stopped doing allocations entirely, we'd wait indefinitely, and stall the worker task. This may also result in the appropriate warnings if CONFIG_DETECT_HUNG_TASK=y. Therefore, introduce a 1 second timeout and use wait_event_timeout(). If the timeout is reached, the static branch is disabled and a new delayed work is scheduled to try setting up an allocation at a later time. Note that, this scenario is very unlikely during normal workloads once the kernel has booted and user space tasks are running. It can, however, happen during early boot after KFENCE has been enabled, when e.g. running tests that do not result in any allocations. Link: https://lkml.kernel.org/r/CADYN=9J0DQhizAGB0-jz4HOBBh+05kMBXb4c0cXMS7Qi5NAJiw@mail.gmail.com Link: https://lkml.kernel.org/r/20201110135320.3309507-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reported-by: Anders Roxell <anders.roxell@linaro.org> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: SeongJae Park <sjpark@amazon.de> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Bug: 177201466 (cherry picked from commit 80d4693491f6f20de01437319b081fdda2079e67 https://github.com/hnaz/linux-mm v5.11-rc4-mmots-2021-01-21-20-10) Test: CONFIG_KFENCE_KUNIT_TEST=y passes on Cuttlefish Signed-off-by: Alexander Potapenko <glider@google.com> Change-Id: I2332ff8144b8bce5c4574b01ea2863e0e71e6124
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.
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.