5.4-stable review patch. If anyone has any objections, please let me know.
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From: Rafael J. Wysocki rafael.j.wysocki@intel.com
commit 69e5d50fcf4093fb3f9f41c4f931f12c2ca8c467 upstream.
The cpufreq_cpu_put() call in update_qos_request() takes place too early because the latter subsequently calls freq_qos_update_request() that indirectly accesses the policy object in question through the QoS request object passed to it.
Fortunately, update_qos_request() is called under intel_pstate_driver_lock, so this issue does not matter for changing the intel_pstate operation mode, but it theoretically can cause a crash to occur on CPU device hot removal (which currently can only happen in virt, but it is formally supported nevertheless).
Address this issue by modifying update_qos_request() to drop the reference to the policy later.
Fixes: da5c504c7aae ("cpufreq: intel_pstate: Implement QoS supported freq constraints") Cc: 5.4+ stable@vger.kernel.org # 5.4+ Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Zihuan Zhang zhangzihuan@kylinos.cn Link: https://patch.msgid.link/2255671.irdbgypaU6@rafael.j.wysocki Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/cpufreq/intel_pstate.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1092,10 +1092,10 @@ static void update_qos_request(enum freq continue;
req = policy->driver_data; - cpufreq_cpu_put(policy); - - if (!req) + if (!req) { + cpufreq_cpu_put(policy); continue; + }
if (hwp_active) intel_pstate_get_hwp_max(i, &turbo_max, &max_state); @@ -1114,6 +1114,8 @@ static void update_qos_request(enum freq
if (freq_qos_update_request(req, freq) < 0) pr_warn("Failed to update freq constraint: CPU%d\n", i); + + cpufreq_cpu_put(policy); } }