From: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com
[ Upstream commit 68b99e94a4a2db6ba9b31fe0485e057b9354a640 ]
When CPU 0 is offline and intel_powerclamp is used to inject idle, it generates kernel BUG:
BUG: using smp_processor_id() in preemptible [00000000] code: bash/15687 caller is debug_smp_processor_id+0x17/0x20 CPU: 4 PID: 15687 Comm: bash Not tainted 5.19.0-rc7+ #57 Call Trace: <TASK> dump_stack_lvl+0x49/0x63 dump_stack+0x10/0x16 check_preemption_disabled+0xdd/0xe0 debug_smp_processor_id+0x17/0x20 powerclamp_set_cur_state+0x7f/0xf9 [intel_powerclamp] ... ...
Here CPU 0 is the control CPU by default and changed to the current CPU, if CPU 0 offlined. This check has to be performed under cpus_read_lock(), hence the above warning.
Use get_cpu() instead of smp_processor_id() to avoid this BUG.
Suggested-by: Chen Yu yu.c.chen@intel.com Signed-off-by: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com [ rjw: Subject edits ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/thermal/intel_powerclamp.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c index 8e8328347c0e..079c8c1a5f15 100644 --- a/drivers/thermal/intel_powerclamp.c +++ b/drivers/thermal/intel_powerclamp.c @@ -550,8 +550,10 @@ static int start_power_clamp(void)
/* prefer BSP */ control_cpu = 0; - if (!cpu_online(control_cpu)) - control_cpu = smp_processor_id(); + if (!cpu_online(control_cpu)) { + control_cpu = get_cpu(); + put_cpu(); + }
clamping = true; schedule_delayed_work(&poll_pkg_cstate_work, 0);