From 9228169d2ae055ed09a163887fc59a710a5eb73b Mon Sep 17 00:00:00 2001 From: K Prateek Nayak Date: Fri, 8 May 2026 05:17:43 +0000 Subject: [PATCH] cpufreq/amd-pstate: Grab "amd_pstate_driver_lock" when toggling dynamic_epp Concurrently changing driver mode and dynamic_epp with: echo passive > /sys/devices/system/cpu/amd_pstate/status& echo disable > /sys/devices/system/cpu/amd_pstate/dynamic_epp& hits the WARN_ON_ONCE() in static_key_disable_cpuslocked() and hangs the system since both sysfs writes are trying to do amd_pstate_change_driver_mode() without any synchronization. Grab the "amd_pstate_driver_lock" mutex when modifying "dynamic_epp" to prevent the two paths from racing with each other. Add a lockdep assertion for "amd_pstate_driver_lock" in amd_pstate_change_driver_mode() to formalize the dependency. Since "cppc_mode" is stable under "amd_pstate_driver_lock", only reload the driver when in "AMD_PSTATE_ACTIVE" mode and reject all writes when in passive or guided mode, or if the driver is not loaded, since only active mode operates on EPP. Fixes: e30ca6dd5345 ("cpufreq/amd-pstate: Add dynamic energy performance preference") Reviewed-by: Mario Limonciello Signed-off-by: K Prateek Nayak Link: https://lore.kernel.org/r/20260508051748.10484-2-kprateek.nayak@amd.com Signed-off-by: Mario Limonciello (AMD) --- drivers/cpufreq/amd-pstate.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index 453084c67327..5e2d28c73294 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -1707,6 +1707,8 @@ static int amd_pstate_change_driver_mode(int mode) { int ret; + lockdep_assert_held(&amd_pstate_driver_lock); + ret = amd_pstate_unregister_driver(0); if (ret) return ret; @@ -1821,6 +1823,13 @@ static ssize_t dynamic_epp_store(struct device *a, struct device_attribute *b, if (ret) return ret; + guard(mutex)(&amd_pstate_driver_lock); + + if (cppc_state != AMD_PSTATE_ACTIVE) { + pr_debug("dynamic_epp can only be toggled in active mode\n"); + return -EINVAL; + } + if (dynamic_epp == enabled) return -EINVAL;