From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (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 3tBxKT6fThzDsrT for ; Mon, 7 Nov 2016 13:31:57 +1100 (AEDT) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uA72SduZ124437 for ; Sun, 6 Nov 2016 21:31:55 -0500 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0a-001b2d01.pphosted.com with ESMTP id 26jb2havxs-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 06 Nov 2016 21:31:55 -0500 Received: from localhost by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 6 Nov 2016 19:31:54 -0700 Date: Mon, 7 Nov 2016 08:01:47 +0530 From: Gautham R Shenoy To: Denis Kirjanov Cc: linuxppc-dev@lists.ozlabs.org, ego@linux.vnet.ibm.com Subject: Re: [PATCH v2] ppc: cpufreq: disable preemption while checking CPU throttling state Reply-To: ego@linux.vnet.ibm.com References: <1478257718-14923-1-git-send-email-kda@linux-powerpc.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1478257718-14923-1-git-send-email-kda@linux-powerpc.org> Message-Id: <20161107023147.GA14131@in.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Denis, On Fri, Nov 04, 2016 at 07:08:38AM -0400, Denis Kirjanov wrote: You can provide the config option with which this bug was found in the change log. I suppose you had enabled CONFIG_DEBUG_PREEMPT. > [ 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 > > v2: wrap powernv_cpufreq_throttle_check() > as suggested by Gautham R Shenoy Looks good otherwise. Reviewed-by: Gautham R. Shenoy > --- > drivers/cpufreq/powernv-cpufreq.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index d3ffde8..112e0e2 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -647,8 +647,15 @@ 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 >