diff options
| author | K Prateek Nayak <kprateek.nayak@amd.com> | 2026-05-08 08:17:43 +0300 |
|---|---|---|
| committer | Mario Limonciello (AMD) <superm1@kernel.org> | 2026-05-08 08:30:50 +0300 |
| commit | 9228169d2ae055ed09a163887fc59a710a5eb73b (patch) | |
| tree | 6a13efe5ea884eafe7d2b562c91eb7b65c7befb9 | |
| parent | 7fd2df204f342fc17d1a0bfcd474b24232fb0f32 (diff) | |
| download | linux-9228169d2ae055ed09a163887fc59a710a5eb73b.tar.xz | |
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 <mario.limonciello@amd.com>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20260508051748.10484-2-kprateek.nayak@amd.com
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
| -rw-r--r-- | drivers/cpufreq/amd-pstate.c | 9 |
1 files changed, 9 insertions, 0 deletions
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; |