From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:40528 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751885AbdARK4J (ORCPT ); Wed, 18 Jan 2017 05:56:09 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Gautham R. Shenoy" , Denis Kirjanov , "Rafael J. Wysocki" Subject: [PATCH 4.9 101/120] cpufreq: powernv: Disable preemption while checking CPU throttling state Date: Wed, 18 Jan 2017 11:46:59 +0100 Message-Id: <20170118104652.257172750@linuxfoundation.org> In-Reply-To: <20170118104648.120216880@linuxfoundation.org> References: <20170118104648.120216880@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Denis Kirjanov 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 Signed-off-by: Denis Kirjanov Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/cpufreq/powernv-cpufreq.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -647,8 +647,14 @@ static int powernv_cpufreq_target_index( 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());