From: K Prateek Nayak Date: Mon, 16 Mar 2026 08:18:49 +0000 (+0000) Subject: cpufreq: Pass the policy to cpufreq_driver->adjust_perf() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c03791085adcd61fa9b766ab303c7d0941d7378d;p=thirdparty%2Flinux.git cpufreq: Pass the policy to cpufreq_driver->adjust_perf() 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: 1d215f0319c2 ("cpufreq: amd-pstate: Add fast switch function for AMD P-State") Reported-by: Bert Karwatzki Acked-by: Viresh Kumar Signed-off-by: K Prateek Nayak Acked-by: Gary Guo # Rust Reviewed-by: Gautham R. Shenoy Reviewed-by: Zhongqiu Han Link: https://lore.kernel.org/r/20260316081849.19368-3-kprateek.nayak@amd.com Signed-off-by: Mario Limonciello (AMD) --- diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index 2ea4d27fe020c..c825fab0bf5c1 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -788,13 +788,12 @@ static unsigned int amd_pstate_fast_switch(struct cpufreq_policy *policy, return policy->cur; } -static void amd_pstate_adjust_perf(unsigned int cpu, +static void amd_pstate_adjust_perf(struct cpufreq_policy *policy, unsigned long _min_perf, unsigned long target_perf, unsigned long capacity) { u8 max_perf, min_perf, des_perf, cap_perf; - struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpu); struct amd_cpudata *cpudata; union perf_cached perf; diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 277884d91913c..90e939069cde4 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -2231,7 +2231,7 @@ EXPORT_SYMBOL_GPL(cpufreq_driver_fast_switch); /** * cpufreq_driver_adjust_perf - Adjust CPU performance level in one go. - * @cpu: Target CPU. + * @policy: cpufreq policy object of the target CPU. * @min_perf: Minimum (required) performance level (units of @capacity). * @target_perf: Target (desired) performance level (units of @capacity). * @capacity: Capacity of the target CPU. @@ -2250,12 +2250,12 @@ EXPORT_SYMBOL_GPL(cpufreq_driver_fast_switch); * parallel with either ->target() or ->target_index() or ->fast_switch() for * the same CPU. */ -void cpufreq_driver_adjust_perf(unsigned int cpu, +void cpufreq_driver_adjust_perf(struct cpufreq_policy *policy, unsigned long min_perf, unsigned long target_perf, unsigned long capacity) { - cpufreq_driver->adjust_perf(cpu, min_perf, target_perf, capacity); + cpufreq_driver->adjust_perf(policy, min_perf, target_perf, capacity); } /** diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 11c58af419006..0f50034e4b680 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -3239,12 +3239,12 @@ static unsigned int intel_cpufreq_fast_switch(struct cpufreq_policy *policy, return target_pstate * cpu->pstate.scaling; } -static void intel_cpufreq_adjust_perf(unsigned int cpunum, +static void intel_cpufreq_adjust_perf(struct cpufreq_policy *policy, unsigned long min_perf, unsigned long target_perf, unsigned long capacity) { - struct cpudata *cpu = all_cpu_data[cpunum]; + struct cpudata *cpu = all_cpu_data[policy->cpu]; u64 hwp_cap = READ_ONCE(cpu->hwp_cap_cached); int old_pstate = cpu->pstate.current_pstate; int cap_pstate, min_pstate, max_pstate, target_pstate; diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index cc894fc389710..4317c5a312bd1 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -372,7 +372,7 @@ struct cpufreq_driver { * conditions) scale invariance can be disabled, which causes the * schedutil governor to fall back to the latter. */ - void (*adjust_perf)(unsigned int cpu, + void (*adjust_perf)(struct cpufreq_policy *policy, unsigned long min_perf, unsigned long target_perf, unsigned long capacity); @@ -617,7 +617,7 @@ struct cpufreq_governor { /* Pass a target to the cpufreq driver */ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy, unsigned int target_freq); -void cpufreq_driver_adjust_perf(unsigned int cpu, +void cpufreq_driver_adjust_perf(struct cpufreq_policy *policy, unsigned long min_perf, unsigned long target_perf, unsigned long capacity); diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 153232dd8276a..ae9fd211cec1f 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -461,6 +461,7 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time, unsigned int flags) { struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util); + struct sugov_policy *sg_policy = sg_cpu->sg_policy; unsigned long prev_util = sg_cpu->util; unsigned long max_cap; @@ -482,10 +483,10 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time, if (sugov_hold_freq(sg_cpu) && sg_cpu->util < prev_util) sg_cpu->util = prev_util; - cpufreq_driver_adjust_perf(sg_cpu->cpu, sg_cpu->bw_min, + cpufreq_driver_adjust_perf(sg_policy->policy, sg_cpu->bw_min, sg_cpu->util, max_cap); - sg_cpu->sg_policy->last_freq_update_time = time; + sg_policy->last_freq_update_time = time; } static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs index f5adee48d40cb..d8d26870bea2e 100644 --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -1257,18 +1257,17 @@ impl Registration { /// # Safety /// /// - This function may only be called from the cpufreq C infrastructure. + /// - The pointer arguments must be valid pointers. unsafe extern "C" fn adjust_perf_callback( - cpu: c_uint, + ptr: *mut bindings::cpufreq_policy, min_perf: c_ulong, target_perf: c_ulong, capacity: c_ulong, ) { - // SAFETY: The C API guarantees that `cpu` refers to a valid CPU number. - let cpu_id = unsafe { CpuId::from_u32_unchecked(cpu) }; - - if let Ok(mut policy) = PolicyCpu::from_cpu(cpu_id) { - T::adjust_perf(&mut policy, min_perf, target_perf, capacity); - } + // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the + // lifetime of `policy`. + let policy = unsafe { Policy::from_raw_mut(ptr) }; + T::adjust_perf(policy, min_perf, target_perf, capacity); } /// Driver's `get_intermediate` callback.