Patch "thermal: intel_powerclamp: Use get_cpu() instead of smp_processor_id() to avoid crash" has been added to the 6.0-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    thermal: intel_powerclamp: Use get_cpu() instead of smp_processor_id() to avoid crash

to the 6.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     thermal-intel_powerclamp-use-get_cpu-instead-of-smp_.patch
and it can be found in the queue-6.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 6a426b935640cefbc23dd425023ff1832cfc6c77
Author: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Date:   Tue Sep 20 04:06:57 2022 -0700

    thermal: intel_powerclamp: Use get_cpu() instead of smp_processor_id() to avoid crash
    
    [ 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@xxxxxxxxx>
    Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
    [ rjw: Subject edits ]
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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);