From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:46040 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932743AbeCSJPs (ORCPT ); Mon, 19 Mar 2018 05:15:48 -0400 Subject: Patch "sched: Stop resched_cpu() from sending IPIs to offline CPUs" has been added to the 3.18-stable tree To: paulmck@linux.vnet.ibm.com Cc: , From: Date: Mon, 19 Mar 2018 10:13:21 +0100 Message-ID: <1521450801203217@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled sched: Stop resched_cpu() from sending IPIs to offline CPUs to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sched-stop-resched_cpu-from-sending-ipis-to-offline-cpus.patch and it can be found in the queue-3.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Mon Mar 19 10:11:52 CET 2018 From: "Paul E. McKenney" Date: Fri, 13 Oct 2017 16:24:28 -0700 Subject: sched: Stop resched_cpu() from sending IPIs to offline CPUs From: "Paul E. McKenney" [ Upstream commit a0982dfa03efca6c239c52cabebcea4afb93ea6b ] The rcutorture test suite occasionally provokes a splat due to invoking resched_cpu() on an offline CPU: WARNING: CPU: 2 PID: 8 at /home/paulmck/public_git/linux-rcu/arch/x86/kernel/smp.c:128 native_smp_send_reschedule+0x37/0x40 Modules linked in: CPU: 2 PID: 8 Comm: rcu_preempt Not tainted 4.14.0-rc4+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 task: ffff902ede9daf00 task.stack: ffff96c50010c000 RIP: 0010:native_smp_send_reschedule+0x37/0x40 RSP: 0018:ffff96c50010fdb8 EFLAGS: 00010096 RAX: 000000000000002e RBX: ffff902edaab4680 RCX: 0000000000000003 RDX: 0000000080000003 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: ffff96c50010fdb8 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 00000000299f36ae R12: 0000000000000001 R13: ffffffff9de64240 R14: 0000000000000001 R15: ffffffff9de64240 FS: 0000000000000000(0000) GS:ffff902edfc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000f7d4c642 CR3: 000000001e0e2000 CR4: 00000000000006e0 Call Trace: resched_curr+0x8f/0x1c0 resched_cpu+0x2c/0x40 rcu_implicit_dynticks_qs+0x152/0x220 force_qs_rnp+0x147/0x1d0 ? sync_rcu_exp_select_cpus+0x450/0x450 rcu_gp_kthread+0x5a9/0x950 kthread+0x142/0x180 ? force_qs_rnp+0x1d0/0x1d0 ? kthread_create_on_node+0x40/0x40 ret_from_fork+0x27/0x40 Code: 14 01 0f 92 c0 84 c0 74 14 48 8b 05 14 4f f4 00 be fd 00 00 00 ff 90 a0 00 00 00 5d c3 89 fe 48 c7 c7 38 89 ca 9d e8 e5 56 08 00 <0f> ff 5d c3 0f 1f 44 00 00 8b 05 52 9e 37 02 85 c0 75 38 55 48 ---[ end trace 26df9e5df4bba4ac ]--- This splat cannot be generated by expedited grace periods because they always invoke resched_cpu() on the current CPU, which is good because expedited grace periods require that resched_cpu() unconditionally succeed. However, other parts of RCU can tolerate resched_cpu() acting as a no-op, at least as long as it doesn't happen too often. This commit therefore makes resched_cpu() invoke resched_curr() only if the CPU is either online or is the current CPU. Signed-off-by: Paul E. McKenney Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/sched/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -633,7 +633,8 @@ void resched_cpu(int cpu) unsigned long flags; raw_spin_lock_irqsave(&rq->lock, flags); - resched_curr(rq); + if (cpu_online(cpu) || cpu == smp_processor_id()) + resched_curr(rq); raw_spin_unlock_irqrestore(&rq->lock, flags); } Patches currently in stable-queue which might be from paulmck@linux.vnet.ibm.com are queue-3.18/sched-stop-resched_cpu-from-sending-ipis-to-offline-cpus.patch queue-3.18/rcutorture-configinit-fix-build-directory-error-message.patch