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K Prateek Nayak
e52830bf37
[ Upstream commitc03791085a] cpufreq_cpu_get() can sleep on PREEMPT_RT in presence of concurrent writer(s), however amd-pstate depends on fetching the cpudata via the policy's driver data which necessitates grabbing the reference. Since schedutil governor can call "cpufreq_driver->update_perf()" during sched_tick/enqueue/dequeue with rq_lock held and IRQs disabled, fetching the policy object using the cpufreq_cpu_get() helper in the scheduler fast-path leads to "BUG: scheduling while atomic" on PREEMPT_RT [1]. Pass the cached cpufreq policy object in sg_policy to the update_perf() instead of just the CPU. The CPU can be inferred using "policy->cpu". The lifetime of cpufreq_policy object outlasts that of the governor and the cpufreq driver (allocated when the CPU is onlined and only reclaimed when the CPU is offlined / the CPU device is removed) which makes it safe to be referenced throughout the governor's lifetime. Closes:https://lore.kernel.org/all/20250731092316.3191-1-spasswolf@web.de/ [1] Fixes:1d215f0319("cpufreq: amd-pstate: Add fast switch function for AMD P-State") Reported-by: Bert Karwatzki <spasswolf@web.de> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com> Acked-by: Gary Guo <gary@garyguo.net> # Rust Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com> Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com> Link: https://lore.kernel.org/r/20260316081849.19368-3-kprateek.nayak@amd.com Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org> 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 reStructuredText 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.