Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753422AbbEZNGQ (ORCPT ); Tue, 26 May 2015 09:06:16 -0400 Received: from [62.245.222.98] ([62.245.222.98]:53436 "EHLO mail.bmw-carit.de" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752655AbbEZNGL (ORCPT ); Tue, 26 May 2015 09:06:11 -0400 X-CTCH-RefID: str=0001.0A0C0201.55645E62.033C,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 Message-ID: <55645E62.2070507@bmw-carit.de> Date: Tue, 26 May 2015 13:52:02 +0200 From: Daniel Wagner User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Steven Rostedt , Ingo Molnar , Peter Zijlstra CC: "linux-kernel@vger.kernel.org" Subject: Re: lockdep warning: threadirqs and preemptoff tracer References: <555C49D8.8030009@bmw-carit.de> In-Reply-To: <555C49D8.8030009@bmw-carit.de> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5222 Lines: 95 On 05/20/2015 10:46 AM, Daniel Wagner wrote: > [ 206.610079] ------------[ cut here ]------------ > [ 206.610122] WARNING: CPU: 0 PID: 3 at kernel/locking/lockdep.c:3574 check_flags.part.36+0x1bc/0x210() > [ 206.610166] DEBUG_LOCKS_WARN_ON(current->softirqs_enabled) > [ 206.610192] Modules linked in: > [ 206.610224] x86_pkg_temp_thermal coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel iTCO_wdt iTCO_vendor_support ipmi_devintf dcdbas joydev tpm_tis pcspkr acpi_pad ipmi_si ipmi_msghandler acpi_power_meter wmi mei_me tpm sb_edac shpchp edac_core mei lpc_ich mfd_core nfsd auth_rpcgss nfs_acl lockd grace sunrpc xfs libcrc32c mgag200 drm_kms_helper ttm drm ixgbe igb mdio vxlan ip6_udp_tunnel udp_tunnel megaraid_sas ptp pps_core dca i2c_algo_bit > [ 206.610892] CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.1.0-rc4 #99 > [ 206.610952] Hardware name: Dell Inc. PowerEdge R820/066N7P, BIOS 2.0.20 01/16/2014 > [ 206.611021] ffffffff8186e017 000000005a61066b ffff881fb11d3b28 ffffffff8186e017 > [ 206.611118] 0000000000000000 ffff881fb11d3b80 ffff881fb11d3b68 ffffffff810af8fa > [ 206.611211] ffff881fb11d3b88 ffffffff81e6cb58 0000000000000000 0000000000000000 > [ 206.611302] Call Trace: > [ 206.611338] [] ? dump_stack+0x4f/0x7b > [ 206.611392] [] dump_stack+0x4f/0x7b > [ 206.611448] [] warn_slowpath_common+0x8a/0xc0 > [ 206.611507] [] warn_slowpath_fmt+0x55/0x70 > [ 206.611565] [] ? warn_slowpath_fmt+0x5/0x70 > [ 206.611623] [] check_flags.part.36+0x1bc/0x210 > [ 206.611682] [] lock_acquire+0x199/0x2d0 > [ 206.611738] [] ? _raw_spin_lock_irqsave+0x2b/0xa0 > [ 206.611800] [] ? preempt_count_add+0x5/0xc0 > [ 206.611860] [] _raw_spin_lock_irqsave+0x59/0xa0 > [ 206.611922] [] ? check_critical_timing+0xae/0x170 > [ 206.611982] [] ? _raw_spin_lock_irqsave+0x5/0xa0 > [ 206.612043] [] check_critical_timing+0xae/0x170 > [ 206.612102] [] ? __do_softirq+0x24c/0x6b0 > [ 206.612158] [] ? __local_bh_enable+0x3b/0x70 > [ 206.612213] [] ? __do_softirq+0x24c/0x6b0 > [ 206.612266] [] ? __local_bh_enable+0x3b/0x70 > [ 206.612322] [] trace_preempt_on+0x101/0x120 > [ 206.612376] [] ? preempt_count_sub+0x5/0xf0 > [ 206.612431] [] preempt_count_sub+0xab/0xf0 > [ 206.612485] [] ? __local_bh_enable+0x3b/0x70 > [ 206.612540] [] __local_bh_enable+0x3b/0x70 > [ 206.612595] [] ? __do_softirq+0x24c/0x6b0 > [ 206.612649] [] __do_softirq+0x24c/0x6b0 > [ 206.612703] [] run_ksoftirqd+0x25/0x70 > [ 206.614370] [] smpboot_thread_fn+0x193/0x2a0 > [ 206.616013] [] ? sort_range+0x30/0x30 > [ 206.616948] [] kthread+0x104/0x120 > [ 206.617733] [] ? wait_for_completion+0xd3/0x140 > [ 206.618512] [] ? kthread_create_on_node+0x260/0x260 > [ 206.619281] [] ret_from_fork+0x42/0x70 > [ 206.620054] [] ? kthread_create_on_node+0x260/0x260 > [ 206.620831] ---[ end trace 9e22068fb8699756 ]--- > [ 206.621607] irq event stamp: 636192 > [ 206.622362] hardirqs last enabled at (636190): [] _raw_spin_unlock_irqrestore+0x65/0x90 > [ 206.623140] hardirqs last disabled at (636191): [] __do_softirq+0x1de/0x6b0 > [ 206.623904] softirqs last enabled at (636192): [] __do_softirq+0x24c/0x6b0 > [ 206.624653] softirqs last disabled at (635925): [] run_ksoftirqd+0x25/0x70 I starred for a while at the code and saw the comment in __local_bh_disable_ip(): /* * The preempt tracer hooks into preempt_count_add and will break * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET * is set and before current->softirq_enabled is cleared. * We must manually increment preempt_count here and manually * call the trace_preempt_off later. */ >From this I figured this might be the same problem just in the enable path. The below patch made the lockdep warning disappear. Though I am not sure what I breaking with this. diff --git a/kernel/softirq.c b/kernel/softirq.c index 479e443..6fc0449 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -128,9 +128,13 @@ static void __local_bh_enable(unsigned int cnt) { WARN_ON_ONCE(!irqs_disabled()); + if (preempt_count() == cnt) + trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); + if (softirq_count() == (cnt & SOFTIRQ_MASK)) trace_softirqs_on(_RET_IP_); - preempt_count_sub(cnt); + + __preempt_count_sub(cnt); } /* cheers, daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/