[PATCH] ppc: cpufreq: Use get_cpu()/put_cpu() instead of smp_processor_id() to avoid the oops

[Denis Kirjanov]

[   67.700897] BUG: using smp_processor_id() in preemptible [00000000] code: cat/7343
[   67.700988] caller is .powernv_cpufreq_throttle_check+0x2c/0x710
[   67.700998] CPU: 13 PID: 7343 Comm: cat Not tainted 4.8.0-rc5-dirty #1
[   67.701038] Call Trace:
[   67.701066] [c0000007d25b75b0] [c000000000971378] .dump_stack+0xe4/0x150 (unreliable)
[   67.701153] [c0000007d25b7640] [c0000000005162e4] .check_preemption_disabled+0x134/0x150
[   67.701238] [c0000007d25b76e0] [c0000000007b63ac] .powernv_cpufreq_throttle_check+0x2c/0x710
[   67.701322] [c0000007d25b7790] [c0000000007b6d18] .powernv_cpufreq_target_index+0x288/0x360
[   67.701407] [c0000007d25b7870] [c0000000007acee4] .__cpufreq_driver_target+0x394/0x8c0
[   67.701491] [c0000007d25b7920] [c0000000007b22ac] .cpufreq_set+0x7c/0xd0
[   67.701565] [c0000007d25b79b0] [c0000000007adf50] .store_scaling_setspeed+0x80/0xc0
[   67.701650] [c0000007d25b7a40] [c0000000007ae270] .store+0xa0/0x100
[   67.701723] [c0000007d25b7ae0] [c0000000003566e8] .sysfs_kf_write+0x88/0xb0
[   67.701796] [c0000007d25b7b70] [c0000000003553b8] .kernfs_fop_write+0x178/0x260
[   67.701881] [c0000007d25b7c10] [c0000000002ac3cc] .__vfs_write+0x3c/0x1c0
[   67.701954] [c0000007d25b7cf0] [c0000000002ad584] .vfs_write+0xc4/0x230
[   67.702027] [c0000007d25b7d90] [c0000000002aeef8] .SyS_write+0x58/0x100
[   67.702101] [c0000007d25b7e30] [c00000000000bfec] system_call+0x38/0xfc

Signed-off-by: Denis Kirjanov <kda at linux-powerpc.org>
---
 drivers/cpufreq/powernv-cpufreq.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index d3ffde8..4cd91a3 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -475,7 +475,7 @@ static inline unsigned int get_nominal_index(void)
 static void powernv_cpufreq_throttle_check(void *data)
 {
 	struct chip *chip;
-	unsigned int cpu = smp_processor_id();
+	int cpu;
 	unsigned long pmsr;
 	int pmsr_pmax;
 	unsigned int pmsr_pmax_idx;
@@ -491,9 +491,11 @@ static void powernv_cpufreq_throttle_check(void *data)
 			goto next;
 		chip->throttled = true;
 		if (pmsr_pmax_idx > powernv_pstate_info.nominal) {
+			cpu = get_cpu();
 			pr_warn_once("CPU %d on Chip %u has Pmax(%d) reduced below nominal frequency(%d)\n",
 				     cpu, chip->id, pmsr_pmax,
 				     idx_to_pstate(powernv_pstate_info.nominal));
+			put_cpu();
 			chip->throttle_sub_turbo++;
 		} else {
 			chip->throttle_turbo++;
-- 
1.8.3.1