From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3t8nld6p2wzDvRR for ; Fri, 4 Nov 2016 01:43:41 +1100 (AEDT) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uA3EeY5j020878 for ; Thu, 3 Nov 2016 10:43:38 -0400 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0a-001b2d01.pphosted.com with ESMTP id 26g6j6k3nr-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 03 Nov 2016 10:43:38 -0400 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 3 Nov 2016 10:43:37 -0400 Date: Thu, 3 Nov 2016 20:13:33 +0530 From: Gautham R Shenoy To: Denis Kirjanov Cc: linuxppc-dev@lists.ozlabs.org, Shilpasri G Bhat , Akshay Adiga , Vaidyanathan Srinivasan Subject: Re: [PATCH] ppc: cpufreq: Use get_cpu()/put_cpu() instead of smp_processor_id() to avoid the oops Reply-To: ego@linux.vnet.ibm.com References: <1478172041-9067-1-git-send-email-kda@linux-powerpc.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1478172041-9067-1-git-send-email-kda@linux-powerpc.org> Message-Id: <20161103144333.GA28138@in.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Denis, On Thu, Nov 03, 2016 at 07:20:41AM -0400, Denis Kirjanov wrote: > [ 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 Thanks for looking into this! > --- > 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) The powernv_cpufreq_throttle_check() checks if the frequency on any of the CPUs on this chip has been throttled. Hence it needs to be executed without preemption on a CPU on the particular chip. It is called in two places currently: a) powernv_cpufreq_work_fn where it is called via smp_call_function_any() which will ensure that the function will be executed without preempted. b) from powernv_cpufreq_target_index: Here it should be nested within the preempt_disable() preempt_enable() calls. It currently is not. So, I would suggest fixing b) instead of locally fixing smp_processor_id() to get_cpu()/put_cpu(). > { > 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 > -- Thanks and Regards gautham.