| From f96eb661cf559ec2eed641aceec5f676de222d2f Mon Sep 17 00:00:00 2001 |
| From: Denis Kirjanov <kda@linux-powerpc.org> |
| Date: Tue, 8 Nov 2016 05:39:28 -0500 |
| Subject: [PATCH] cpufreq: powernv: Disable preemption while checking CPU |
| throttling state |
| |
| commit 8a10c06a20ec8097a68fd7a4a1c0e285095b4d2f upstream. |
| |
| With preemption turned on we can read incorrect throttling state |
| while being switched to CPU on a different chip. |
| |
| BUG: using smp_processor_id() in preemptible [00000000] code: cat/7343 |
| caller is .powernv_cpufreq_throttle_check+0x2c/0x710 |
| CPU: 13 PID: 7343 Comm: cat Not tainted 4.8.0-rc5-dirty #1 |
| Call Trace: |
| [c0000007d25b75b0] [c000000000971378] .dump_stack+0xe4/0x150 (unreliable) |
| [c0000007d25b7640] [c0000000005162e4] .check_preemption_disabled+0x134/0x150 |
| [c0000007d25b76e0] [c0000000007b63ac] .powernv_cpufreq_throttle_check+0x2c/0x710 |
| [c0000007d25b7790] [c0000000007b6d18] .powernv_cpufreq_target_index+0x288/0x360 |
| [c0000007d25b7870] [c0000000007acee4] .__cpufreq_driver_target+0x394/0x8c0 |
| [c0000007d25b7920] [c0000000007b22ac] .cpufreq_set+0x7c/0xd0 |
| [c0000007d25b79b0] [c0000000007adf50] .store_scaling_setspeed+0x80/0xc0 |
| [c0000007d25b7a40] [c0000000007ae270] .store+0xa0/0x100 |
| [c0000007d25b7ae0] [c0000000003566e8] .sysfs_kf_write+0x88/0xb0 |
| [c0000007d25b7b70] [c0000000003553b8] .kernfs_fop_write+0x178/0x260 |
| [c0000007d25b7c10] [c0000000002ac3cc] .__vfs_write+0x3c/0x1c0 |
| [c0000007d25b7cf0] [c0000000002ad584] .vfs_write+0xc4/0x230 |
| [c0000007d25b7d90] [c0000000002aeef8] .SyS_write+0x58/0x100 |
| [c0000007d25b7e30] [c00000000000bfec] system_call+0x38/0xfc |
| |
| Fixes: 09a972d16209 (cpufreq: powernv: Report cpu frequency throttling) |
| Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> |
| Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org> |
| Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c |
| index d3ffde806629..a84724eabfb8 100644 |
| --- a/drivers/cpufreq/powernv-cpufreq.c |
| +++ b/drivers/cpufreq/powernv-cpufreq.c |
| @@ -647,8 +647,14 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy, |
| if (unlikely(rebooting) && new_index != get_nominal_index()) |
| return 0; |
| |
| - if (!throttled) |
| + if (!throttled) { |
| + /* we don't want to be preempted while |
| + * checking if the CPU frequency has been throttled |
| + */ |
| + preempt_disable(); |
| powernv_cpufreq_throttle_check(NULL); |
| + preempt_enable(); |
| + } |
| |
| cur_msec = jiffies_to_msecs(get_jiffies_64()); |
| |
| -- |
| 2.10.1 |
| |
