From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46442 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733220AbgFWTma (ORCPT ); Tue, 23 Jun 2020 15:42:30 -0400 Date: Tue, 23 Jun 2020 21:41:32 +0200 From: Peter Zijlstra Subject: Re: [PATCH v4 7/8] lockdep: Change hardirq{s_enabled,_context} to per-cpu variables Message-ID: <20200623194132.GC2483@worktop.programming.kicks-ass.net> References: <20200623083645.277342609@infradead.org> <20200623083721.512673481@infradead.org> <20200623150031.GA2986783@debian-buster-darwi.lab.linutronix.de> <20200623152450.GM4817@hirez.programming.kicks-ass.net> <20200623161320.GA2996373@debian-buster-darwi.lab.linutronix.de> <20200623163730.GA4800@hirez.programming.kicks-ass.net> <20200623175957.GA106514@elver.google.com> <20200623181232.GB4800@hirez.programming.kicks-ass.net> <20200623191335.GA86296@elver.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200623191335.GA86296@elver.google.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Marco Elver Cc: "Ahmed S. Darwish" , Ingo Molnar , Will Deacon , Thomas Gleixner , the arch/x86 maintainers , LKML , Steven Rostedt , bigeasy@linutronix.de, "David S. Miller" , sparclinux@vger.kernel.org, Michael Ellerman , linuxppc-dev@lists.ozlabs.org, heiko.carstens@de.ibm.com, linux-s390@vger.kernel.org, linux@armlinux.org.uk, Qian Cai On Tue, Jun 23, 2020 at 09:13:35PM +0200, Marco Elver wrote: > I see the below report when I boot with your branch + KCSAN and > PROVE_LOCKING. config attached. Trying to make sense of what's > happening. Ah, I was still playing with tip/master + PROVE_LOCKING + KCSAN and slowly removing parts of that annotation patch to see what would come unstuck. I think I just hit a genuine but unavoidable lockdep report on report_lock. > ------ >8 ------ > > [ 10.182354] ------------[ cut here ]------------ > [ 10.183058] WARNING: CPU: 7 PID: 136 at kernel/locking/lockdep.c:398 lockdep_hardirqs_on_prepare+0x1c6/0x270 > [ 10.184347] Modules linked in: > [ 10.184771] CPU: 7 PID: 136 Comm: systemd-journal Not tainted 5.8.0-rc1+ #3 > [ 10.185706] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 > [ 10.186821] RIP: 0010:lockdep_hardirqs_on_prepare+0x1c6/0x270 > [ 10.187594] Code: 75 28 65 48 8b 04 25 28 00 00 00 48 3b 44 24 08 0f 85 b9 00 00 00 48 83 c4 10 5b 41 5e 41 5f c3 65 48 ff 05 d4 24 4e 75 eb d8 <0f> 0b 90 41 c7 86 c4 08 00 00 00 00 00 00 eb c8 e8 65 09 71 01 85 > [ 10.190203] RSP: 0018:ffffa7ee802b7848 EFLAGS: 00010017 > [ 10.190989] RAX: 0000000000000001 RBX: ffff955e92a34ab0 RCX: 0000000000000001 > [ 10.192053] RDX: 0000000000000006 RSI: ffff955e92a34a88 RDI: ffff955e92a341c0 > [ 10.193117] RBP: ffffa7ee802b7be8 R08: 0000000000000000 R09: 0000ffffffffffff > [ 10.194186] R10: 0000ffffffffffff R11: 0000ffff8d07e268 R12: 0000000000000001 > [ 10.195249] R13: ffffffff8e41bb10 R14: ffff955e92a341c0 R15: 0000000000000001 > [ 10.196312] FS: 00007fd6862aa8c0(0000) GS:ffff955e9fd80000(0000) knlGS:0000000000000000 > [ 10.197513] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 10.198373] CR2: 00007fd6837dd000 CR3: 0000000812acc001 CR4: 0000000000760ee0 > [ 10.199436] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 10.200494] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 10.201554] PKRU: 55555554 > [ 10.201967] Call Trace: > [ 10.202348] ? _raw_spin_unlock_irqrestore+0x40/0x70 > [ 10.203093] trace_hardirqs_on+0x56/0x60 <----- enter IRQ flags tracing code? > [ 10.203686] _raw_spin_unlock_irqrestore+0x40/0x70 <----- take report_lock > [ 10.204406] prepare_report+0x11f/0x150 > [ 10.204986] kcsan_report+0xca/0x6c0 <----- generating a KCSAN report > [ 10.212669] kcsan_found_watchpoint+0xe5/0x110 That appears to be warning about a lockdep_recursion underflow, weird. I'll go stare at it.