mirrors/linux
2
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-05-16 02:01:18 -04:00
Code Issues Packages Projects Releases Wiki Activity

cpufreq: Pass the policy to cpufreq_driver->adjust_perf()

Browse Source 
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>
This commit is contained in:
K Prateek Nayak
2026-03-16 08:18:49 +00:00
committed by Mario Limonciello (AMD)
parent 86d71f1d76
commit c03791085a
6 changed files with 17 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/cpufreq/amd-pstate.c
View File

@@ -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;

6
drivers/cpufreq/cpufreq.c
View File

@@ -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);
}
/**

4
drivers/cpufreq/intel_pstate.c
View File

@@ -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;

4
include/linux/cpufreq.h
View File

@@ -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);

5
kernel/sched/cpufreq_schedutil.c
View File

@@ -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)

13
rust/kernel/cpufreq.rs
View File

@@ -1257,18 +1257,17 @@ impl<T: Driver> Registration<T> {
/// # 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.