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e78a7614f3
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> |
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| .. | ||
| autogroup.c | ||
| autogroup.h | ||
| clock.c | ||
| completion.c | ||
| core.c | ||
| cpuacct.c | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpufreq_schedutil.c | ||
| cpufreq.c | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle.c | ||
| isolation.c | ||
| loadavg.c | ||
| Makefile | ||
| membarrier.c | ||
| pelt.c | ||
| pelt.h | ||
| psi.c | ||
| rt.c | ||
| sched-pelt.h | ||
| sched.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| swait.c | ||
| topology.c | ||
| wait_bit.c | ||
| wait.c | ||