• Paul E. McKenney's avatar
    mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls · 0a3b3c25
    Paul E. McKenney authored
    A large process running on a heavily loaded system can encounter the
    following RCU CPU stall warning:
    
      rcu: INFO: rcu_sched self-detected stall on CPU
      rcu: 	3-....: (20998 ticks this GP) idle=4ea/1/0x4000000000000002 softirq=556558/556558 fqs=5190
      	(t=21013 jiffies g=1005461 q=132576)
      NMI backtrace for cpu 3
      CPU: 3 PID: 501900 Comm: aio-free-ring-w Kdump: loaded Not tainted 5.2.9-108_fbk12_rc3_3858_gb83b75af7909 #1
      Hardware name: Wiwynn   HoneyBadger/PantherPlus, BIOS HBM6.71 02/03/2016
      Call Trace:
       <IRQ>
       dump_stack+0x46/0x60
       nmi_cpu_backtrace.cold.3+0x13/0x50
       ? lapic_can_unplug_cpu.cold.27+0x34/0x34
       nmi_trigger_cpumask_backtrace+0xba/0xca
       rcu_dump_cpu_stacks+0x99/0xc7
       rcu_sched_clock_irq.cold.87+0x1aa/0x397
       ? tick_sched_do_timer+0x60/0x60
       update_process_times+0x28/0x60
       tick_sched_timer+0x37/0x70
       __hrtimer_run_queues+0xfe/0x270
       hrtimer_interrupt+0xf4/0x210
       smp_apic_timer_interrupt+0x5e/0x120
       apic_timer_interrupt+0xf/0x20
       </IRQ>
      RIP: 0010:kmem_cache_free+0x223/0x300
      Code: 88 00 00 00 0f 85 ca 00 00 00 41 8b 55 18 31 f6 f7 da 41 f6 45 0a 02 40 0f 94 c6 83 c6 05 9c 41 5e fa e8 a0 a7 01 00 41 56 9d <49> 8b 47 08 a8 03 0f 85 87 00 00 00 65 48 ff 08 e9 3d fe ff ff 65
      RSP: 0018:ffffc9000e8e3da8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
      RAX: 0000000000020000 RBX: ffff88861b9de960 RCX: 0000000000000030
      RDX: fffffffffffe41e8 RSI: 000060777fe3a100 RDI: 000000000001be18
      RBP: ffffea00186e7780 R08: ffffffffffffffff R09: ffffffffffffffff
      R10: ffff88861b9dea28 R11: ffff88887ffde000 R12: ffffffff81230a1f
      R13: ffff888854684dc0 R14: 0000000000000206 R15: ffff8888547dbc00
       ? remove_vma+0x4f/0x60
       remove_vma+0x4f/0x60
       exit_mmap+0xd6/0x160
       mmput+0x4a/0x110
       do_exit+0x278/0xae0
       ? syscall_trace_enter+0x1d3/0x2b0
       ? handle_mm_fault+0xaa/0x1c0
       do_group_exit+0x3a/0xa0
       __x64_sys_exit_group+0x14/0x20
       do_syscall_64+0x42/0x100
       entry_SYSCALL_64_after_hwframe+0x44/0xa9
    
    And on a PREEMPT=n kernel, the "while (vma)" loop in exit_mmap() can run
    for a very long time given a large process.  This commit therefore adds
    a cond_resched() to this loop, providing RCU any needed quiescent states.
    
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: <linux-mm@kvack.org>
    Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
    Reviewed-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
    0a3b3c25
mmap.c 101 KB