Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752697AbdI1Jhn (ORCPT ); Thu, 28 Sep 2017 05:37:43 -0400 Received: from mail-qt0-f196.google.com ([209.85.216.196]:33021 "EHLO mail-qt0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751580AbdI1Jhm (ORCPT ); Thu, 28 Sep 2017 05:37:42 -0400 X-Google-Smtp-Source: AOwi7QCtZ/1Q1Uq3kj0P2/yOaNcYRlSuYyaUI0VwisWmcjk7Ypas+5yWAHqq8XLAOnHjE+1F1jpvfN6Xyi4NCx0dJGE= MIME-Version: 1.0 In-Reply-To: <1492621117-13939-40-git-send-email-paulmck@linux.vnet.ibm.com> References: <20170419165805.GB10874@linux.vnet.ibm.com> <1492621117-13939-40-git-send-email-paulmck@linux.vnet.ibm.com> From: Sasha Levin Date: Thu, 28 Sep 2017 02:37:20 -0700 Message-ID: Subject: Re: [PATCH v3 tip/core/rcu 40/40] rcu: Make non-preemptive schedule be Tasks RCU quiescent state To: "Paul E. McKenney" Cc: "linux-kernel@vger.kernel.org List" , Ingo Molnar , jiangshanlai@gmail.com, dipankar@in.ibm.com, Andrew Morton , Mathieu Desnoyers , Josh Triplett , Thomas Gleixner , Peter Zijlstra , Steven Rostedt , dhowells@redhat.com, Eric Dumazet , =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , Oleg Nesterov , bobby.prani@gmail.com, alexander.levin@verizon.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4331 Lines: 88 On Wed, Apr 19, 2017 at 9:58 AM, Paul E. McKenney wrote: > Currently, a call to schedule() acts as a Tasks RCU quiescent state > only if a context switch actually takes place. However, just the > call to schedule() guarantees that the calling task has moved off of > whatever tracing trampoline that it might have been one previously. > This commit therefore plumbs schedule()'s "preempt" parameter into > rcu_note_context_switch(), which then records the Tasks RCU quiescent > state, but only if this call to schedule() was -not- due to a preemption. > > To avoid adding overhead to the common-case context-switch path, > this commit hides the rcu_note_context_switch() check under an existing > non-common-case check. > > Suggested-by: Steven Rostedt > Signed-off-by: Paul E. McKenney Hey Paul, I'm seeing the following on the latest -next kernel, and suspect it's caused bit this patch: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 6974 at kernel/rcu/tree_plugin.h:329 rcu_preempt_note_context_switch kernel/rcu/tree_plugin.h:329 [inline] WARNING: CPU: 0 PID: 6974 at kernel/rcu/tree_plugin.h:329 rcu_note_context_switch+0x16c/0x2210 kernel/rcu/tree.c:458 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 6974 Comm: syz-fuzzer Not tainted 4.13.0-next-20170908+ #246 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-1ubuntu1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x11d/0x1e5 lib/dump_stack.c:52 panic+0x1bc/0x3b7 kernel/panic.c:181 __warn+0x1c4/0x1d9 kernel/panic.c:542 report_bug+0x211/0x2d0 lib/bug.c:183 fixup_bug+0x3f/0x90 arch/x86/kernel/traps.c:178 do_trap_no_signal arch/x86/kernel/traps.c:212 [inline] do_trap+0x260/0x390 arch/x86/kernel/traps.c:261 do_error_trap+0x133/0x380 arch/x86/kernel/traps.c:298 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311 invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905 RIP: 0010:rcu_preempt_note_context_switch kernel/rcu/tree_plugin.h:329 [inline] RIP: 0010:rcu_note_context_switch+0x16c/0x2210 kernel/rcu/tree.c:458 RSP: 0018:ffff88003b2debc8 EFLAGS: 00010002 RAX: 0000000000000001 RBX: 1ffff1000765bd85 RCX: 0000000000000000 RDX: 1ffff100075d7882 RSI: ffffffffb5c7da20 RDI: ffff88003aebc410 RBP: ffff88003b2def30 R08: dffffc0000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000000 R12: ffff88003b2def08 R13: 0000000000000000 R14: ffff88003aebc040 R15: ffff88003aebc040 __schedule+0x201/0x2240 kernel/sched/core.c:3292 schedule+0x113/0x460 kernel/sched/core.c:3421 kvm_async_pf_task_wait+0x43f/0x940 arch/x86/kernel/kvm.c:158 do_async_page_fault+0x72/0x90 arch/x86/kernel/kvm.c:271 async_page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1069 RIP: 0010:format_decode+0x240/0x830 lib/vsprintf.c:1996 RSP: 0018:ffff88003b2df520 EFLAGS: 00010283 RAX: 000000000000003f RBX: ffffffffb5d1e141 RCX: ffff88003b2df670 RDX: 0000000000000001 RSI: dffffc0000000000 RDI: ffffffffb5d1e140 RBP: ffff88003b2df560 R08: dffffc0000000000 R09: 0000000000000000 R10: ffff88003b2df718 R11: 0000000000000000 R12: ffff88003b2df5d8 R13: 0000000000000064 R14: ffffffffb5d1e140 R15: 0000000000000000 vsnprintf+0x173/0x1700 lib/vsprintf.c:2136 sprintf+0xbe/0xf0 lib/vsprintf.c:2386 proc_self_get_link+0xfb/0x1c0 fs/proc/self.c:23 get_link fs/namei.c:1047 [inline] link_path_walk+0x1041/0x1490 fs/namei.c:2127 path_openat+0x2d0/0x3600 fs/namei.c:3527 do_filp_open+0x263/0x3c0 fs/namei.c:3562 do_sys_open+0x515/0x6f0 fs/open.c:1059 SYSC_openat fs/open.c:1086 [inline] SyS_openat+0x30/0x40 fs/open.c:1080 do_syscall_64+0x26a/0x800 arch/x86/entry/common.c:287 entry_SYSCALL64_slow_path+0x25/0x25 RIP: 0033:0x4889da RSP: 002b:000000c4261eb8f0 EFLAGS: 00000206 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004889da RDX: 0000000000000002 RSI: 000000c42338d2c0 RDI: ffffffffffffff9c RBP: 000000c4261eb980 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 R13: 00000000ffffffee R14: 00000000000012c0 R15: 0000000000000100 Dumping ftrace buffer: (ftrace buffer empty) Kernel Offset: 0x30000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) Rebooting in 86400 seconds..