From mboxrd@z Thu Jan 1 00:00:00 1970 From: Denis Kirjanov Subject: [PATCH v2] cpufreq, powernv: Disable preemption while checking CPU throttling state throttling state Date: Tue, 8 Nov 2016 05:39:28 -0500 Message-ID: <1478601568-15728-1-git-send-email-kda@linux-powerpc.org> Return-path: Received: from mail-lf0-f68.google.com ([209.85.215.68]:32937 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752837AbcKHKlX (ORCPT ); Tue, 8 Nov 2016 05:41:23 -0500 Received: by mail-lf0-f68.google.com with SMTP id 98so7418828lfs.0 for ; Tue, 08 Nov 2016 02:41:22 -0800 (PST) Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: rjw@rjwysocki.net, viresh.kumar@linaro.org Cc: linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, ego@linux.vnet.ibm.com, shilpa.bhat@linux.vnet.ibm.com, akshay.adiga@linux.vnet.ibm.com, Denis Kirjanov With preemption turned on we can read incorrect throttling state while being switched to CPU on a different chip. [ 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 Fixes: 09a972d16209 ("cpufreq: powernv: Report cpu frequency throttling") Reviewed-by: Gautham R. Shenoy Signed-off-by: Denis Kirjanov --- v2: added patch description drivers/cpufreq/powernv-cpufreq.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index d3ffde8..a84724e 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()); -- 1.8.3.1