• Paul E. McKenney's avatar
    mm: Place preemption point in do_mlockall() loop · 5c889690
    Paul E. McKenney authored
    There is a loop in do_mlockall() that lacks a preemption point, which
    means that the following can happen on non-preemptible builds of the
    kernel:
    
    > My fuzz tester keeps hitting this. Every instance shows the non-irq stack
    > came in from mlockall.  I'm only seeing this on one box, but that has more
    > ram (8gb) than my other machines, which might explain it.
    >
    > 	Dave
    >
    > INFO: rcu_preempt self-detected stall on CPU { 3}  (t=6500 jiffies g=470344 c=470343 q=0)
    > sending NMI to all CPUs:
    > NMI backtrace for cpu 3
    > CPU: 3 PID: 29664 Comm: trinity-child2 Not tainted 3.11.0-rc1+ #32
    > task: ffff88023e743fc0 ti: ffff88022f6f2000 task.ti: ffff88022f6f2000
    > RIP: 0010:[<ffffffff810bf7d1>]  [<ffffffff810bf7d1>] trace_hardirqs_off_caller+0x21/0xb0
    > RSP: 0018:ffff880244e03c30  EFLAGS: 00000046
    > RAX: ffff88023e743fc0 RBX: 0000000000000001 RCX: 000000000000003c
    > RDX: 000000000000000f RSI: 0000000000000004 RDI: ffffffff81033cab
    > RBP: ffff880244e03c38 R08: ffff880243288a80 R09: 0000000000000001
    > R10: 0000000000000000 R11: 0000000000000001 R12: ffff880243288a80
    > R13: ffff8802437eda40 R14: 0000000000080000 R15: 000000000000d010
    > FS:  00007f50ae33b740(0000) GS:ffff880244e00000(0000) knlGS:0000000000000000
    > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    > CR2: 000000000097f000 CR3: 0000000240fa0000 CR4: 00000000001407e0
    > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
    > Stack:
    >  ffffffff810bf86d ffff880244e03c98 ffffffff81033cab 0000000000000096
    >  000000000000d008 0000000300000002 0000000000000004 0000000000000003
    >  0000000000002710 ffffffff81c50d00 ffffffff81c50d00 ffff880244fcde00
    > Call Trace:
    >  <IRQ>
    >  [<ffffffff810bf86d>] ? trace_hardirqs_off+0xd/0x10
    >  [<ffffffff81033cab>] __x2apic_send_IPI_mask+0x1ab/0x1c0
    >  [<ffffffff81033cdc>] x2apic_send_IPI_all+0x1c/0x20
    >  [<ffffffff81030115>] arch_trigger_all_cpu_backtrace+0x65/0xa0
    >  [<ffffffff811144b1>] rcu_check_callbacks+0x331/0x8e0
    >  [<ffffffff8108bfa0>] ? hrtimer_run_queues+0x20/0x180
    >  [<ffffffff8109e905>] ? sched_clock_cpu+0xb5/0x100
    >  [<ffffffff81069557>] update_process_times+0x47/0x80
    >  [<ffffffff810bd115>] tick_sched_handle.isra.16+0x25/0x60
    >  [<ffffffff810bd231>] tick_sched_timer+0x41/0x60
    >  [<ffffffff8108ace1>] __run_hrtimer+0x81/0x4e0
    >  [<ffffffff810bd1f0>] ? tick_sched_do_timer+0x60/0x60
    >  [<ffffffff8108b93f>] hrtimer_interrupt+0xff/0x240
    >  [<ffffffff8102de84>] local_apic_timer_interrupt+0x34/0x60
    >  [<ffffffff81718c5f>] smp_apic_timer_interrupt+0x3f/0x60
    >  [<ffffffff817178ef>] apic_timer_interrupt+0x6f/0x80
    >  [<ffffffff8170e8e0>] ? retint_restore_args+0xe/0xe
    >  [<ffffffff8105f101>] ? __do_softirq+0xb1/0x440
    >  [<ffffffff8105f64d>] irq_exit+0xcd/0xe0
    >  [<ffffffff81718c65>] smp_apic_timer_interrupt+0x45/0x60
    >  [<ffffffff817178ef>] apic_timer_interrupt+0x6f/0x80
    >  <EOI>
    >  [<ffffffff8170e8e0>] ? retint_restore_args+0xe/0xe
    >  [<ffffffff8170b830>] ? wait_for_completion_killable+0x170/0x170
    >  [<ffffffff8170c853>] ? preempt_schedule_irq+0x53/0x90
    >  [<ffffffff8170e9f6>] retint_kernel+0x26/0x30
    >  [<ffffffff8107a523>] ? queue_work_on+0x43/0x90
    >  [<ffffffff8107c369>] schedule_on_each_cpu+0xc9/0x1a0
    >  [<ffffffff81167770>] ? lru_add_drain+0x50/0x50
    >  [<ffffffff811677c5>] lru_add_drain_all+0x15/0x20
    >  [<ffffffff81186965>] SyS_mlockall+0xa5/0x1a0
    >  [<ffffffff81716e94>] tracesys+0xdd/0xe2
    
    This commit addresses this problem by inserting the required preemption
    point.
    Reported-by: default avatarDave Jones <davej@redhat.com>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
    Cc: Michel Lespinasse <walken@google.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    5c889690
mlock.c 21.2 KB