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While thinking about sporadic failures of perf_pmu/rc6-runtime-pm* tests on some CI machines I have concluded that: a) the PMU readout of RC6 can race against runtime PM transitions, and b) there are other reasons than being runtime suspended which can cause intel_runtime_pm_get_if_in_use to fail. Therefore when estimating RC6 the code needs to assert we are indeed in suspended state, and if not, the best we can do is return the last known RC6 value. Without this check we can calculate the estimated value based on un- initialized or inappropriate internal state, which can result in over- estimation, or in any case incorrect value being returned. v2: * Re-arrange the code a bit to avoid second unlock and return branch. (Chris Wilson) v3: * Insert some strategic blank lines and improve commit msg. (Chris Wilson) Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Fixes:1fe699e301("drm/i915/pmu: Fix sleep under atomic in RC6 readout") Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105010 Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Imre Deak <imre.deak@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Link: https://patchwork.freedesktop.org/patch/msgid/20180410112704.24462-1-tvrtko.ursulin@linux.intel.com (cherry picked from commit2924bdee21) Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.