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[ Upstream commit55eb9a6c8b] The test_klp_callbacks_busy module conditionally blocks a future livepatch transition by busy waiting inside its workqueue function, busymod_work_func(). After scheduling this work, a test livepatch is loaded, introducing the transition under test. Both events are marked in the kernel log for later verification, but there is no synchronization to ensure that busymod_work_func() logs its function entry message before subsequent selftest commands log their own messages. This can lead to a rare test failure due to unexpected ordering like: # --- expected # +++ result # @@ -1,7 +1,7 @@ # % modprobe test_klp_callbacks_busy block_transition=Y # test_klp_callbacks_busy: test_klp_callbacks_busy_init # -test_klp_callbacks_busy: busymod_work_func enter # % modprobe test_klp_callbacks_demo # +test_klp_callbacks_busy: busymod_work_func enter # livepatch: enabling patch 'test_klp_callbacks_demo' # livepatch: 'test_klp_callbacks_demo': initializing patching transition # test_klp_callbacks_demo: pre_patch_callback: vmlinux Force the module init function to wait until busymod_work_func() has started (and logged its message), before exiting to the next selftest steps. Fixes:547840bd5a("selftests/livepatch: simplify test-klp-callbacks busy target tests") Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20220602203233.979681-1-joe.lawrence@redhat.com Signed-off-by: Sasha Levin <sashal@kernel.org>
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.