| From aa5c0a983f5e70491e2285f9db6f924b7e453992 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 5 Jun 2019 07:46:43 -0700 |
| Subject: idle: Prevent late-arriving interrupts from disrupting offline |
| |
| From: Peter Zijlstra <peterz@infradead.org> |
| |
| [ Upstream commit e78a7614f3876ac649b3df608789cb6ef74d0480 ] |
| |
| Scheduling-clock interrupts can arrive late in the CPU-offline process, |
| after idle entry and the subsequent call to cpuhp_report_idle_dead(). |
| Once execution passes the call to rcu_report_dead(), RCU is ignoring |
| the CPU, which results in lockdep complaints when the interrupt handler |
| uses RCU: |
| |
| ------------------------------------------------------------------------ |
| |
| ============================= |
| WARNING: suspicious RCU usage |
| 5.2.0-rc1+ #681 Not tainted |
| ----------------------------- |
| kernel/sched/fair.c:9542 suspicious rcu_dereference_check() usage! |
| |
| other info that might help us debug this: |
| |
| RCU used illegally from offline CPU! |
| rcu_scheduler_active = 2, debug_locks = 1 |
| no locks held by swapper/5/0. |
| |
| stack backtrace: |
| CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.2.0-rc1+ #681 |
| Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Bochs 01/01/2011 |
| Call Trace: |
| <IRQ> |
| dump_stack+0x5e/0x8b |
| trigger_load_balance+0xa8/0x390 |
| ? tick_sched_do_timer+0x60/0x60 |
| update_process_times+0x3b/0x50 |
| tick_sched_handle+0x2f/0x40 |
| tick_sched_timer+0x32/0x70 |
| __hrtimer_run_queues+0xd3/0x3b0 |
| hrtimer_interrupt+0x11d/0x270 |
| ? sched_clock_local+0xc/0x74 |
| smp_apic_timer_interrupt+0x79/0x200 |
| apic_timer_interrupt+0xf/0x20 |
| </IRQ> |
| RIP: 0010:delay_tsc+0x22/0x50 |
| Code: ff 0f 1f 80 00 00 00 00 65 44 8b 05 18 a7 11 48 0f ae e8 0f 31 48 89 d6 48 c1 e6 20 48 09 c6 eb 0e f3 90 65 8b 05 fe a6 11 48 <41> 39 c0 75 18 0f ae e8 0f 31 48 c1 e2 20 48 09 c2 48 89 d0 48 29 |
| RSP: 0000:ffff8f92c0157ed0 EFLAGS: 00000212 ORIG_RAX: ffffffffffffff13 |
| RAX: 0000000000000005 RBX: ffff8c861f356400 RCX: ffff8f92c0157e64 |
| RDX: 000000321214c8cc RSI: 00000032120daa7f RDI: 0000000000260f15 |
| RBP: 0000000000000005 R08: 0000000000000005 R09: 0000000000000000 |
| R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000 |
| R13: 0000000000000000 R14: ffff8c861ee18000 R15: ffff8c861ee18000 |
| cpuhp_report_idle_dead+0x31/0x60 |
| do_idle+0x1d5/0x200 |
| ? _raw_spin_unlock_irqrestore+0x2d/0x40 |
| cpu_startup_entry+0x14/0x20 |
| start_secondary+0x151/0x170 |
| secondary_startup_64+0xa4/0xb0 |
| |
| ------------------------------------------------------------------------ |
| |
| This happens rarely, but can be forced by happen more often by |
| placing delays in cpuhp_report_idle_dead() following the call to |
| rcu_report_dead(). With this in place, the following rcutorture |
| scenario reproduces the problem within a few minutes: |
| |
| tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 8 --duration 5 --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y" --configs "TREE04" |
| |
| This commit uses the crude but effective expedient of moving the disabling |
| of interrupts within the idle loop to precede the cpu_is_offline() |
| check. It also invokes tick_nohz_idle_stop_tick() instead of |
| tick_nohz_idle_stop_tick_protected() to shut off the scheduling-clock |
| interrupt. |
| |
| Signed-off-by: Peter Zijlstra <peterz@infradead.org> |
| Cc: Frederic Weisbecker <fweisbec@gmail.com> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: Ingo Molnar <mingo@kernel.org> |
| [ paulmck: Revert tick_nohz_idle_stop_tick_protected() removal, new callers. ] |
| Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| kernel/sched/idle.c | 5 +++-- |
| 1 file changed, 3 insertions(+), 2 deletions(-) |
| |
| diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c |
| index 80940939b7336..e4bc4aa739b83 100644 |
| --- a/kernel/sched/idle.c |
| +++ b/kernel/sched/idle.c |
| @@ -241,13 +241,14 @@ static void do_idle(void) |
| check_pgt_cache(); |
| rmb(); |
| |
| + local_irq_disable(); |
| + |
| if (cpu_is_offline(cpu)) { |
| - tick_nohz_idle_stop_tick_protected(); |
| + tick_nohz_idle_stop_tick(); |
| cpuhp_report_idle_dead(); |
| arch_cpu_idle_dead(); |
| } |
| |
| - local_irq_disable(); |
| arch_cpu_idle_enter(); |
| |
| /* |
| -- |
| 2.20.1 |
| |
