* [PATCH] thermal/drivers/intel_powerclamp: Fix bug for smp_processor_id
@ 2022-09-20 11:06 Srinivas Pandruvada
2022-09-21 18:28 ` Rafael J. Wysocki
0 siblings, 1 reply; 2+ messages in thread
From: Srinivas Pandruvada @ 2022-09-20 11:06 UTC (permalink / raw)
To: rafael, rui.zhang, daniel.lezcano
Cc: linux-pm, linux-kernel, Srinivas Pandruvada, Chen Yu
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>
---
drivers/thermal/intel/intel_powerclamp.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/thermal/intel/intel_powerclamp.c b/drivers/thermal/intel/intel_powerclamp.c
index c841ab37e7c6..46cd799af148 100644
--- a/drivers/thermal/intel/intel_powerclamp.c
+++ b/drivers/thermal/intel/intel_powerclamp.c
@@ -532,8 +532,10 @@ 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);
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] thermal/drivers/intel_powerclamp: Fix bug for smp_processor_id
2022-09-20 11:06 [PATCH] thermal/drivers/intel_powerclamp: Fix bug for smp_processor_id Srinivas Pandruvada
@ 2022-09-21 18:28 ` Rafael J. Wysocki
0 siblings, 0 replies; 2+ messages in thread
From: Rafael J. Wysocki @ 2022-09-21 18:28 UTC (permalink / raw)
To: Srinivas Pandruvada
Cc: Rafael J. Wysocki, Zhang, Rui, Daniel Lezcano, Linux PM,
Linux Kernel Mailing List, Chen Yu
On Tue, Sep 20, 2022 at 1:07 PM Srinivas Pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
> 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>
> ---
> drivers/thermal/intel/intel_powerclamp.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/thermal/intel/intel_powerclamp.c b/drivers/thermal/intel/intel_powerclamp.c
> index c841ab37e7c6..46cd799af148 100644
> --- a/drivers/thermal/intel/intel_powerclamp.c
> +++ b/drivers/thermal/intel/intel_powerclamp.c
> @@ -532,8 +532,10 @@ 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);
> --
Applied as 6.1 material with modified subject, thanks!
^ permalink raw reply [flat|nested] 2+ messages in thread
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