2.6.39-rc6-mmotm0506 - lockdep splat in RCU code on page fault

DISCUSSION [email protected] 3 participants 10 messages May 10, 2011 – May 13, 2011

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2011-05-10 01:05 UTC #0 lore raw

Seen at boot earlier today. Interrupt, page fault, RCU, scheduler, and MM code in the tracebacks. Yee-hah.

[   12.872150] usb 1-4: new high speed USB device number 3 using ehci_hcd
[   12.986667] usb 1-4: New USB device found, idVendor=413c, idProduct=2513
[   12.986679] usb 1-4: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[   12.987691] hub 1-4:1.0: USB hub found
[   12.987877] hub 1-4:1.0: 3 ports detected
[   12.996372] input: PS/2 Generic Mouse as /devices/platform/i8042/serio1/input/input10
[   13.071471] udevadm used greatest stack depth: 3984 bytes left
[   13.172129] 
[   13.172130] =======================================================
[   13.172425] [ INFO: possible circular locking dependency detected ]
[   13.172650] 2.6.39-rc6-mmotm0506 #1
[   13.172773] -------------------------------------------------------
[   13.172997] blkid/267 is trying to acquire lock:
[   13.173009]  (&p->pi_lock){-.-.-.}, at: [<ffffffff81032d8f>] try_to_wake_up+0x29/0x1aa
[   13.173009] 
[   13.173009] but task is already holding lock:
[   13.173009]  (rcu_node_level_0){..-...}, at: [<ffffffff810901cc>] rcu_cpu_kthread_timer+0x27/0x58
[   13.173009] 
[   13.173009] which lock already depends on the new lock.
[   13.173009] 
[   13.173009] 
[   13.173009] the existing dependency chain (in reverse order) is:
[   13.173009] 
[   13.173009] -> #2 (rcu_node_level_0){..-...}:
[   13.173009]        [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]        [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]        [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]        [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]        [<ffffffff815697f1>] _raw_spin_lock+0x36/0x45
[   13.173009]        [<ffffffff81090794>] rcu_read_unlock_special+0x8c/0x1d5
[   13.173009]        [<ffffffff8109092c>] __rcu_read_unlock+0x4f/0xd7
[   13.173009]        [<ffffffff81027bd3>] rcu_read_unlock+0x21/0x23
[   13.173009]        [<ffffffff8102cc34>] cpuacct_charge+0x6c/0x75
[   13.173009]        [<ffffffff81030cc6>] update_curr+0x101/0x12e
[   13.173009]        [<ffffffff810311d0>] check_preempt_wakeup+0xf7/0x23b
[   13.173009]        [<ffffffff8102acb3>] check_preempt_curr+0x2b/0x68
[   13.173009]        [<ffffffff81031d40>] ttwu_do_wakeup+0x76/0x128
[   13.173009]        [<ffffffff81031e49>] ttwu_do_activate.constprop.63+0x57/0x5c
[   13.173009]        [<ffffffff81031e96>] scheduler_ipi+0x48/0x5d
[   13.173009]        [<ffffffff810177d5>] smp_reschedule_interrupt+0x16/0x18
[   13.173009]        [<ffffffff815710f3>] reschedule_interrupt+0x13/0x20
[   13.173009]        [<ffffffff810b66d1>] rcu_read_unlock+0x21/0x23
[   13.173009]        [<ffffffff810b739c>] find_get_page+0xa9/0xb9
[   13.173009]        [<ffffffff810b8b48>] filemap_fault+0x6a/0x34d
[   13.173009]        [<ffffffff810d1a25>] __do_fault+0x54/0x3e6
[   13.173009]        [<ffffffff810d447a>] handle_pte_fault+0x12c/0x1ed
[   13.173009]        [<ffffffff810d48f7>] handle_mm_fault+0x1cd/0x1e0
[   13.173009]        [<ffffffff8156cfee>] do_page_fault+0x42d/0x5de
[   13.173009]        [<ffffffff8156a75f>] page_fault+0x1f/0x30
[   13.173009] 
[   13.173009] -> #1 (&rq->lock){-.-.-.}:
[   13.173009]        [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]        [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]        [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]        [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]        [<ffffffff815697f1>] _raw_spin_lock+0x36/0x45
[   13.173009]        [<ffffffff81027e19>] __task_rq_lock+0x8b/0xd3
[   13.173009]        [<ffffffff81032f7f>] wake_up_new_task+0x41/0x108
[   13.173009]        [<ffffffff810376c3>] do_fork+0x265/0x33f
[   13.173009]        [<ffffffff81007d02>] kernel_thread+0x6b/0x6d
[   13.173009]        [<ffffffff8153a9dd>] rest_init+0x21/0xd2
[   13.173009]        [<ffffffff81b1db4f>] start_kernel+0x3bb/0x3c6
[   13.173009]        [<ffffffff81b1d29f>] x86_64_start_reservations+0xaf/0xb3
[   13.173009]        [<ffffffff81b1d393>] x86_64_start_kernel+0xf0/0xf7
[   13.173009] 
[   13.173009] -> #0 (&p->pi_lock){-.-.-.}:
[   13.173009]        [<ffffffff81067788>] check_prev_add+0x68/0x20e
[   13.173009]        [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]        [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]        [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]        [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]        [<ffffffff815698ea>] _raw_spin_lock_irqsave+0x44/0x57
[   13.173009]        [<ffffffff81032d8f>] try_to_wake_up+0x29/0x1aa
[   13.173009]        [<ffffffff81032f3c>] wake_up_process+0x10/0x12
[   13.173009]        [<ffffffff810901e9>] rcu_cpu_kthread_timer+0x44/0x58
[   13.173009]        [<ffffffff81045286>] call_timer_fn+0xac/0x1e9
[   13.173009]        [<ffffffff8104556d>] run_timer_softirq+0x1aa/0x1f2
[   13.173009]        [<ffffffff8103e487>] __do_softirq+0x109/0x26a
[   13.173009]        [<ffffffff8157144c>] call_softirq+0x1c/0x30
[   13.173009]        [<ffffffff81003207>] do_softirq+0x44/0xf1
[   13.173009]        [<ffffffff8103e8b9>] irq_exit+0x58/0xc8
[   13.173009]        [<ffffffff81017f5a>] smp_apic_timer_interrupt+0x79/0x87
[   13.173009]        [<ffffffff81570fd3>] apic_timer_interrupt+0x13/0x20
[   13.173009]        [<ffffffff810bd51a>] get_page_from_freelist+0x2aa/0x310
[   13.173009]        [<ffffffff810bdf03>] __alloc_pages_nodemask+0x178/0x243
[   13.173009]        [<ffffffff8101fe2f>] pte_alloc_one+0x1e/0x3a
[   13.173009]        [<ffffffff810d27fe>] __pte_alloc+0x22/0x14b
[   13.173009]        [<ffffffff810d48a8>] handle_mm_fault+0x17e/0x1e0
[   13.173009]        [<ffffffff8156cfee>] do_page_fault+0x42d/0x5de
[   13.173009]        [<ffffffff8156a75f>] page_fault+0x1f/0x30
[   13.173009] 
[   13.173009] other info that might help us debug this:
[   13.173009] 
[   13.173009] Chain exists of:
[   13.173009]   &p->pi_lock --> &rq->lock --> rcu_node_level_0
[   13.173009] 
[   13.173009]  Possible unsafe locking scenario:
[   13.173009] 
[   13.173009]        CPU0                    CPU1
[   13.173009]        ----                    ----
[   13.173009]   lock(rcu_node_level_0);
[   13.173009]                                lock(&rq->lock);
[   13.173009]                                lock(rcu_node_level_0);
[   13.173009]   lock(&p->pi_lock);
[   13.173009] 
[   13.173009]  *** DEADLOCK ***
[   13.173009] 
[   13.173009] 3 locks held by blkid/267:
[   13.173009]  #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff8156cdb4>] do_page_fault+0x1f3/0x5de
[   13.173009]  #1:  (&yield_timer){+.-...}, at: [<ffffffff810451da>] call_timer_fn+0x0/0x1e9
[   13.173009]  #2:  (rcu_node_level_0){..-...}, at: [<ffffffff810901cc>] rcu_cpu_kthread_timer+0x27/0x58
[   13.173009] 
[   13.173009] stack backtrace:
[   13.173009] Pid: 267, comm: blkid Not tainted 2.6.39-rc6-mmotm0506 #1
[   13.173009] Call Trace:
[   13.173009]  <IRQ>  [<ffffffff8154a529>] print_circular_bug+0xc8/0xd9
[   13.173009]  [<ffffffff81067788>] check_prev_add+0x68/0x20e
[   13.173009]  [<ffffffff8100c861>] ? save_stack_trace+0x28/0x46
[   13.173009]  [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]  [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]  [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]  [<ffffffff81032d8f>] ? try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]  [<ffffffff81032d8f>] ? try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff815698ea>] _raw_spin_lock_irqsave+0x44/0x57
[   13.173009]  [<ffffffff81032d8f>] ? try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff81032d8f>] try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff81032f3c>] wake_up_process+0x10/0x12
[   13.173009]  [<ffffffff810901e9>] rcu_cpu_kthread_timer+0x44/0x58
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff81045286>] call_timer_fn+0xac/0x1e9
[   13.173009]  [<ffffffff810451da>] ? del_timer+0x75/0x75
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff8104556d>] run_timer_softirq+0x1aa/0x1f2
[   13.173009]  [<ffffffff8103e487>] __do_softirq+0x109/0x26a
[   13.173009]  [<ffffffff8106365f>] ? tick_dev_program_event+0x37/0xf6
[   13.173009]  [<ffffffff810a0e4a>] ? time_hardirqs_off+0x1b/0x2f
[   13.173009]  [<ffffffff8157144c>] call_softirq+0x1c/0x30
[   13.173009]  [<ffffffff81003207>] do_softirq+0x44/0xf1
[   13.173009]  [<ffffffff8103e8b9>] irq_exit+0x58/0xc8
[   13.173009]  [<ffffffff81017f5a>] smp_apic_timer_interrupt+0x79/0x87
[   13.173009]  [<ffffffff81570fd3>] apic_timer_interrupt+0x13/0x20
[   13.173009]  <EOI>  [<ffffffff810bd384>] ? get_page_from_freelist+0x114/0x310
[   13.173009]  [<ffffffff810bd51a>] ? get_page_from_freelist+0x2aa/0x310
[   13.173009]  [<ffffffff812220e7>] ? clear_page_c+0x7/0x10
[   13.173009]  [<ffffffff810bd1ef>] ? prep_new_page+0x14c/0x1cd
[   13.173009]  [<ffffffff810bd51a>] get_page_from_freelist+0x2aa/0x310
[   13.173009]  [<ffffffff810bdf03>] __alloc_pages_nodemask+0x178/0x243
[   13.173009]  [<ffffffff810d46b9>] ? __pmd_alloc+0x87/0x99
[   13.173009]  [<ffffffff8101fe2f>] pte_alloc_one+0x1e/0x3a
[   13.173009]  [<ffffffff810d46b9>] ? __pmd_alloc+0x87/0x99
[   13.173009]  [<ffffffff810d27fe>] __pte_alloc+0x22/0x14b
[   13.173009]  [<ffffffff810d48a8>] handle_mm_fault+0x17e/0x1e0
[   13.173009]  [<ffffffff8156cfee>] do_page_fault+0x42d/0x5de
[   13.173009]  [<ffffffff810d915f>] ? sys_brk+0x32/0x10c
[   13.173009]  [<ffffffff810a0e4a>] ? time_hardirqs_off+0x1b/0x2f
[   13.173009]  [<ffffffff81065c4f>] ? trace_hardirqs_off_caller+0x3f/0x9c
[   13.173009]  [<ffffffff812235dd>] ? trace_hardirqs_off_thunk+0x3a/0x3c
[   13.173009]  [<ffffffff8156a75f>] page_fault+0x1f/0x30
[   14.010075] usb 5-1: new full speed USB device number 2 using uhci_hcd

Paul E. McKenney

2011-05-10 08:20 UTC #1 lore raw

Quoted 2 lines · On Mon, May 09, 2011 at 09:04:36PM -0400, [email protected] wrote:

Seen at boot earlier today. Interrupt, page fault, RCU, scheduler, and MM code in the tracebacks. Yee-hah.

Hmmmm... Here is an untested patch that breaks this particular deadlock cycle. It feels like there might be more where this one came from, though in theory if you call rcu_read_unlock() with the runqueue locks held, it should be impossible for priority deboosting to be invoked.

Unless someone calls rcu_read_lock() with preemption enabled, then acquires a runqueue lock, and then calls rcu_read_unlock(). I am hoping that no one does this.

Thanx, Paul

------------------------------------------------------------------------

rcu: Avoid acquiring rcu_node locks in timer functions

This commit switches manipulations of the rcu_node ->wakemask field to atomic operations, which allows rcu_cpu_kthread_timer() to avoid acquiring the rcu_node lock. This should avoid the following lockdep splat:

[   12.872150] usb 1-4: new high speed USB device number 3 using ehci_hcd
[   12.986667] usb 1-4: New USB device found, idVendor=413c, idProduct=2513
[   12.986679] usb 1-4: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[   12.987691] hub 1-4:1.0: USB hub found
[   12.987877] hub 1-4:1.0: 3 ports detected
[   12.996372] input: PS/2 Generic Mouse as /devices/platform/i8042/serio1/input/input10
[   13.071471] udevadm used greatest stack depth: 3984 bytes left
[   13.172129]
[   13.172130] =======================================================
[   13.172425] [ INFO: possible circular locking dependency detected ]
[   13.172650] 2.6.39-rc6-mmotm0506 #1
[   13.172773] -------------------------------------------------------
[   13.172997] blkid/267 is trying to acquire lock:
[   13.173009]  (&p->pi_lock){-.-.-.}, at: [<ffffffff81032d8f>] try_to_wake_up+0x29/0x1aa
[   13.173009]
[   13.173009] but task is already holding lock:
[   13.173009]  (rcu_node_level_0){..-...}, at: [<ffffffff810901cc>] rcu_cpu_kthread_timer+0x27/0x58
[   13.173009]
[   13.173009] which lock already depends on the new lock.
[   13.173009]
[   13.173009]
[   13.173009] the existing dependency chain (in reverse order) is:
[   13.173009]
[   13.173009] -> #2 (rcu_node_level_0){..-...}:
[   13.173009]        [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]        [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]        [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]        [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]        [<ffffffff815697f1>] _raw_spin_lock+0x36/0x45
[   13.173009]        [<ffffffff81090794>] rcu_read_unlock_special+0x8c/0x1d5
[   13.173009]        [<ffffffff8109092c>] __rcu_read_unlock+0x4f/0xd7
[   13.173009]        [<ffffffff81027bd3>] rcu_read_unlock+0x21/0x23
[   13.173009]        [<ffffffff8102cc34>] cpuacct_charge+0x6c/0x75
[   13.173009]        [<ffffffff81030cc6>] update_curr+0x101/0x12e
[   13.173009]        [<ffffffff810311d0>] check_preempt_wakeup+0xf7/0x23b
[   13.173009]        [<ffffffff8102acb3>] check_preempt_curr+0x2b/0x68
[   13.173009]        [<ffffffff81031d40>] ttwu_do_wakeup+0x76/0x128
[   13.173009]        [<ffffffff81031e49>] ttwu_do_activate.constprop.63+0x57/0x5c
[   13.173009]        [<ffffffff81031e96>] scheduler_ipi+0x48/0x5d
[   13.173009]        [<ffffffff810177d5>] smp_reschedule_interrupt+0x16/0x18
[   13.173009]        [<ffffffff815710f3>] reschedule_interrupt+0x13/0x20
[   13.173009]        [<ffffffff810b66d1>] rcu_read_unlock+0x21/0x23
[   13.173009]        [<ffffffff810b739c>] find_get_page+0xa9/0xb9
[   13.173009]        [<ffffffff810b8b48>] filemap_fault+0x6a/0x34d
[   13.173009]        [<ffffffff810d1a25>] __do_fault+0x54/0x3e6
[   13.173009]        [<ffffffff810d447a>] handle_pte_fault+0x12c/0x1ed
[   13.173009]        [<ffffffff810d48f7>] handle_mm_fault+0x1cd/0x1e0
[   13.173009]        [<ffffffff8156cfee>] do_page_fault+0x42d/0x5de
[   13.173009]        [<ffffffff8156a75f>] page_fault+0x1f/0x30
[   13.173009]
[   13.173009] -> #1 (&rq->lock){-.-.-.}:
[   13.173009]        [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]        [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]        [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]        [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]        [<ffffffff815697f1>] _raw_spin_lock+0x36/0x45
[   13.173009]        [<ffffffff81027e19>] __task_rq_lock+0x8b/0xd3
[   13.173009]        [<ffffffff81032f7f>] wake_up_new_task+0x41/0x108
[   13.173009]        [<ffffffff810376c3>] do_fork+0x265/0x33f
[   13.173009]        [<ffffffff81007d02>] kernel_thread+0x6b/0x6d
[   13.173009]        [<ffffffff8153a9dd>] rest_init+0x21/0xd2
[   13.173009]        [<ffffffff81b1db4f>] start_kernel+0x3bb/0x3c6
[   13.173009]        [<ffffffff81b1d29f>] x86_64_start_reservations+0xaf/0xb3
[   13.173009]        [<ffffffff81b1d393>] x86_64_start_kernel+0xf0/0xf7
[   13.173009]
[   13.173009] -> #0 (&p->pi_lock){-.-.-.}:
[   13.173009]        [<ffffffff81067788>] check_prev_add+0x68/0x20e
[   13.173009]        [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]        [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]        [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]        [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]        [<ffffffff815698ea>] _raw_spin_lock_irqsave+0x44/0x57
[   13.173009]        [<ffffffff81032d8f>] try_to_wake_up+0x29/0x1aa
[   13.173009]        [<ffffffff81032f3c>] wake_up_process+0x10/0x12
[   13.173009]        [<ffffffff810901e9>] rcu_cpu_kthread_timer+0x44/0x58
[   13.173009]        [<ffffffff81045286>] call_timer_fn+0xac/0x1e9
[   13.173009]        [<ffffffff8104556d>] run_timer_softirq+0x1aa/0x1f2
[   13.173009]        [<ffffffff8103e487>] __do_softirq+0x109/0x26a
[   13.173009]        [<ffffffff8157144c>] call_softirq+0x1c/0x30
[   13.173009]        [<ffffffff81003207>] do_softirq+0x44/0xf1
[   13.173009]        [<ffffffff8103e8b9>] irq_exit+0x58/0xc8
[   13.173009]        [<ffffffff81017f5a>] smp_apic_timer_interrupt+0x79/0x87
[   13.173009]        [<ffffffff81570fd3>] apic_timer_interrupt+0x13/0x20
[   13.173009]        [<ffffffff810bd51a>] get_page_from_freelist+0x2aa/0x310
[   13.173009]        [<ffffffff810bdf03>] __alloc_pages_nodemask+0x178/0x243
[   13.173009]        [<ffffffff8101fe2f>] pte_alloc_one+0x1e/0x3a
[   13.173009]        [<ffffffff810d27fe>] __pte_alloc+0x22/0x14b
[   13.173009]        [<ffffffff810d48a8>] handle_mm_fault+0x17e/0x1e0
[   13.173009]        [<ffffffff8156cfee>] do_page_fault+0x42d/0x5de
[   13.173009]        [<ffffffff8156a75f>] page_fault+0x1f/0x30
[   13.173009]
[   13.173009] other info that might help us debug this:
[   13.173009]
[   13.173009] Chain exists of:
[   13.173009]   &p->pi_lock --> &rq->lock --> rcu_node_level_0
[   13.173009]
[   13.173009]  Possible unsafe locking scenario:
[   13.173009]
[   13.173009]        CPU0                    CPU1
[   13.173009]        ----                    ----
[   13.173009]   lock(rcu_node_level_0);
[   13.173009]                                lock(&rq->lock);
[   13.173009]                                lock(rcu_node_level_0);
[   13.173009]   lock(&p->pi_lock);
[   13.173009]
[   13.173009]  *** DEADLOCK ***
[   13.173009]
[   13.173009] 3 locks held by blkid/267:
[   13.173009]  #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff8156cdb4>] do_page_fault+0x1f3/0x5de
[   13.173009]  #1:  (&yield_timer){+.-...}, at: [<ffffffff810451da>] call_timer_fn+0x0/0x1e9
[   13.173009]  #2:  (rcu_node_level_0){..-...}, at: [<ffffffff810901cc>] rcu_cpu_kthread_timer+0x27/0x58
[   13.173009]
[   13.173009] stack backtrace:
[   13.173009] Pid: 267, comm: blkid Not tainted 2.6.39-rc6-mmotm0506 #1
[   13.173009] Call Trace:
[   13.173009]  <IRQ>  [<ffffffff8154a529>] print_circular_bug+0xc8/0xd9
[   13.173009]  [<ffffffff81067788>] check_prev_add+0x68/0x20e
[   13.173009]  [<ffffffff8100c861>] ? save_stack_trace+0x28/0x46
[   13.173009]  [<ffffffff810679b9>] check_prevs_add+0x8b/0x104
[   13.173009]  [<ffffffff81067da1>] validate_chain+0x36f/0x3ab
[   13.173009]  [<ffffffff8106846b>] __lock_acquire+0x369/0x3e2
[   13.173009]  [<ffffffff81032d8f>] ? try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff81068a0f>] lock_acquire+0xfc/0x14c
[   13.173009]  [<ffffffff81032d8f>] ? try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff815698ea>] _raw_spin_lock_irqsave+0x44/0x57
[   13.173009]  [<ffffffff81032d8f>] ? try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff81032d8f>] try_to_wake_up+0x29/0x1aa
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff81032f3c>] wake_up_process+0x10/0x12
[   13.173009]  [<ffffffff810901e9>] rcu_cpu_kthread_timer+0x44/0x58
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff81045286>] call_timer_fn+0xac/0x1e9
[   13.173009]  [<ffffffff810451da>] ? del_timer+0x75/0x75
[   13.173009]  [<ffffffff810901a5>] ? rcu_check_quiescent_state+0x82/0x82
[   13.173009]  [<ffffffff8104556d>] run_timer_softirq+0x1aa/0x1f2
[   13.173009]  [<ffffffff8103e487>] __do_softirq+0x109/0x26a
[   13.173009]  [<ffffffff8106365f>] ? tick_dev_program_event+0x37/0xf6
[   13.173009]  [<ffffffff810a0e4a>] ? time_hardirqs_off+0x1b/0x2f
[   13.173009]  [<ffffffff8157144c>] call_softirq+0x1c/0x30
[   13.173009]  [<ffffffff81003207>] do_softirq+0x44/0xf1
[   13.173009]  [<ffffffff8103e8b9>] irq_exit+0x58/0xc8
[   13.173009]  [<ffffffff81017f5a>] smp_apic_timer_interrupt+0x79/0x87
[   13.173009]  [<ffffffff81570fd3>] apic_timer_interrupt+0x13/0x20
[   13.173009]  <EOI>  [<ffffffff810bd384>] ? get_page_from_freelist+0x114/0x310
[   13.173009]  [<ffffffff810bd51a>] ? get_page_from_freelist+0x2aa/0x310
[   13.173009]  [<ffffffff812220e7>] ? clear_page_c+0x7/0x10
[   13.173009]  [<ffffffff810bd1ef>] ? prep_new_page+0x14c/0x1cd
[   13.173009]  [<ffffffff810bd51a>] get_page_from_freelist+0x2aa/0x310
[   13.173009]  [<ffffffff810bdf03>] __alloc_pages_nodemask+0x178/0x243
[   13.173009]  [<ffffffff810d46b9>] ? __pmd_alloc+0x87/0x99
[   13.173009]  [<ffffffff8101fe2f>] pte_alloc_one+0x1e/0x3a
[   13.173009]  [<ffffffff810d46b9>] ? __pmd_alloc+0x87/0x99
[   13.173009]  [<ffffffff810d27fe>] __pte_alloc+0x22/0x14b
[   13.173009]  [<ffffffff810d48a8>] handle_mm_fault+0x17e/0x1e0
[   13.173009]  [<ffffffff8156cfee>] do_page_fault+0x42d/0x5de
[   13.173009]  [<ffffffff810d915f>] ? sys_brk+0x32/0x10c
[   13.173009]  [<ffffffff810a0e4a>] ? time_hardirqs_off+0x1b/0x2f
[   13.173009]  [<ffffffff81065c4f>] ? trace_hardirqs_off_caller+0x3f/0x9c
[   13.173009]  [<ffffffff812235dd>] ? trace_hardirqs_off_thunk+0x3a/0x3c
[   13.173009]  [<ffffffff8156a75f>] page_fault+0x1f/0x30
[   14.010075] usb 5-1: new full speed USB device number 2 using uhci_hcd

Reported-by Valdis Kletnieks <[email protected]>

Signed-off-by Paul E. McKenney <[email protected]>

kernel/rcutree.c +7 -6

index 5616b17..20c22c5 100644
@@ -1525,13 +1525,15 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
  */
 static void rcu_cpu_kthread_timer(unsigned long arg)
 {
-	unsigned long flags;
+	unsigned long old;
+	unsigned long new;
 	struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
 	struct rcu_node *rnp = rdp->mynode;
 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->wakemask |= rdp->grpmask;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	do {
+		old = rnp->wakemask;
+		new = old | rdp->grpmask;
+	} while (cmpxchg(&rnp->wakemask, old, new) != old);
 	invoke_rcu_node_kthread(rnp);
 }

@@ -1682,8 +1684,7 @@ static int rcu_node_kthread(void *arg)
 		wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0);
 		rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
 		raw_spin_lock_irqsave(&rnp->lock, flags);
-		mask = rnp->wakemask;
-		rnp->wakemask = 0;
+		mask = xchg(&rnp->wakemask,0);
 		rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
 		for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
 			if ((mask & 0x1) == 0)

--
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Ingo Molnar

2011-05-10 08:57 UTC #2 lore raw

kernel/rcutree.c static void rcu_cpu_kthread_setrt(int cpu, int to_rt) · line 1536

Quoted 7 lines · Paul E. McKenney

kernel/rcutree.c +4 -3

-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->wakemask |= rdp->grpmask;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	do {
+		old = rnp->wakemask;
+		new = old | rdp->grpmask;
+	} while (cmpxchg(&rnp->wakemask, old, new) != old);

Hm, isnt this an inferior version of atomic_or_long() in essence?

Note that atomic_or_long() is x86 only, so a generic one would have to be offered too i suspect, atomic_cmpxchg() driven or so - which would look like the above loop.

Most architectures could offer atomic_or_long() i suspect.

Thanks,

Ingo

Paul E. McKenney

2011-05-10 16:22 UTC #3 lore raw

Quoted 13 lines · Ingo Molnar

Review
Quoted 7 lines · Paul E. McKenney
(quoted diff) +4 -3
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->wakemask |= rdp->grpmask;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	do {
+		old = rnp->wakemask;
+		new = old | rdp->grpmask;
+	} while (cmpxchg(&rnp->wakemask, old, new) != old);
Hm, isnt this an inferior version of atomic_or_long() in essence?

Quoted 5 lines

Note that atomic_or_long() is x86 only, so a generic one would have to be offered too i suspect, atomic_cmpxchg() driven or so - which would look like the above loop.
Most architectures could offer atomic_or_long() i suspect.

Is the following what you had in mind? This (untested) patch provides only the generic function: if this is what you had in mind, I can put together optimized versions for a couple of the architectures.

Thanx, Paul

------------------------------------------------------------------------

arch/x86/Kconfig +3 -0

index cc6c53a..e7c2e69 100644
@@ -171,6 +171,9 @@ config ARCH_HAS_DEFAULT_IDLE
 config ARCH_HAS_CACHE_LINE_SIZE
 	def_bool y
 
+config ARCH_HAS_ATOMIC_OR_LONG
+	def_bool X86_64
+
 config HAVE_SETUP_PER_CPU_AREA
 	def_bool y

include/linux/atomic.h +13 -0

index 96c038e..2fc3222 100644
@@ -34,4 +34,17 @@ static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
 }
 #endif
 
+#ifndef CONFIG_ARCH_HAS_ATOMIC_OR_LONG
+static inline void atomic_or_long(unsigned long *v1, unsigned long v2)
+{
+	unsigned long old;
+	unsigned long new;
+
+	do {
+		old = ACCESS_ONCE(*v1);
+		new = old | v2;
+	} while (cmpxchg(v1, old, new) != old);
+}
+#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR_LONG */
+
 #endif /* _LINUX_ATOMIC_H */

kernel/rcutree.c +2 -7

index 20c22c5..86f44a3 100644
@@ -36,7 +36,7 @@
 #include <linux/interrupt.h>
 #include <linux/sched.h>
 #include <linux/nmi.h>
-#include <asm/atomic.h>
+#include <linux/atomic.h>
 #include <linux/bitops.h>
 #include <linux/module.h>
 #include <linux/completion.h>

@@ -1525,15 +1525,10 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
  */
 static void rcu_cpu_kthread_timer(unsigned long arg)
 {
-	unsigned long old;
-	unsigned long new;
 	struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
 	struct rcu_node *rnp = rdp->mynode;
 
-	do {
-		old = rnp->wakemask;
-		new = old | rdp->grpmask;
-	} while (cmpxchg(&rnp->wakemask, old, new) != old);
+	atomic_or_long(&rnp->wakemask, rdp->grpmask);
 	invoke_rcu_node_kthread(rnp);
 }

Ingo Molnar

2011-05-10 20:44 UTC #4 lore raw

Quoted 18 lines · Paul E. McKenney

Quoted 17 lines · Ingo Molnar
Review
Quoted 7 lines · Paul E. McKenney
(quoted diff) +4 -3
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->wakemask |= rdp->grpmask;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	do {
+		old = rnp->wakemask;
+		new = old | rdp->grpmask;
+	} while (cmpxchg(&rnp->wakemask, old, new) != old);
Hm, isnt this an inferior version of atomic_or_long() in essence?
Note that atomic_or_long() is x86 only, so a generic one would have to be offered too i suspect, atomic_cmpxchg() driven or so - which would look like the above loop.

Quoted 5 lines

Quoted 1 line
Most architectures could offer atomic_or_long() i suspect.
Is the following what you had in mind? This (untested) patch provides only the generic function: if this is what you had in mind, I can put together optimized versions for a couple of the architectures.

Yeah, something like this, except:

include/linux/atomic.h static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint) · line 48

Quoted 12 lines

include/linux/atomic.h +12 -0

+#ifndef CONFIG_ARCH_HAS_ATOMIC_OR_LONG
+static inline void atomic_or_long(unsigned long *v1, unsigned long v2)
+{
+	unsigned long old;
+	unsigned long new;
+
+	do {
+		old = ACCESS_ONCE(*v1);
+		new = old | v2;
+	} while (cmpxchg(v1, old, new) != old);
+}
+#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR_LONG */

Shouldnt that method work on atomic_t (or atomic64_t)?

Thanks,

Ingo

Paul E. McKenney

2011-05-11 07:44 UTC #5 lore raw

Quoted 29 lines · Ingo Molnar

Quoted 18 lines · Paul E. McKenney
Quoted 17 lines · Ingo Molnar
Review
Quoted 7 lines · Paul E. McKenney
(quoted diff) +4 -3
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->wakemask |= rdp->grpmask;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	do {
+		old = rnp->wakemask;
+		new = old | rdp->grpmask;
+	} while (cmpxchg(&rnp->wakemask, old, new) != old);
Hm, isnt this an inferior version of atomic_or_long() in essence?
Note that atomic_or_long() is x86 only, so a generic one would have to be offered too i suspect, atomic_cmpxchg() driven or so - which would look like the above loop.
Quoted 5 lines
Quoted 1 line
Most architectures could offer atomic_or_long() i suspect.
Is the following what you had in mind? This (untested) patch provides only the generic function: if this is what you had in mind, I can put together optimized versions for a couple of the architectures.
Yeah, something like this, except:

Quoted 14 lines

include/linux/atomic.h static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint) · line 48
Quoted 12 lines
include/linux/atomic.h +12 -0
+#ifndef CONFIG_ARCH_HAS_ATOMIC_OR_LONG
+static inline void atomic_or_long(unsigned long *v1, unsigned long v2)
+{
+	unsigned long old;
+	unsigned long new;
+
+	do {
+		old = ACCESS_ONCE(*v1);
+		new = old | v2;
+	} while (cmpxchg(v1, old, new) != old);
+}
+#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR_LONG */
Shouldnt that method work on atomic_t (or atomic64_t)?

Works for me -- and in this case it is quite easy to change existing uses.

Thanx, Paul

[email protected]

author

2011-05-11 23:12 UTC #6 lore raw

In reply to Paul E. McKenney

On Tue, 10 May 2011 01:20:29 PDT, "Paul E. McKenney" said:

Would test, but it doesn't apply cleanly to my -mmotm0506 tree:

Quoted 13 lines

kernel/rcutree.c +2 -1

index 5616b17..20c22c5 100644
@@ -1525,13 +1525,15 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
  */
 static void rcu_cpu_kthread_timer(unsigned long arg)
 {
-	unsigned long flags;
+	unsigned long old;
+	unsigned long new;
 	struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
 	struct rcu_node *rnp = rdp->mynode;

kernel/rcutree.c static void rcu_cpu_kthread_setrt(int cpu, int to_rt) · line 1538

Quoted 10 lines

kernel/rcutree.c +4 -3

 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->wakemask |= rdp->grpmask;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	do {
+		old = rnp->wakemask;
+		new = old | rdp->grpmask;
+	} while (cmpxchg(&rnp->wakemask, old, new) != old);
 	invoke_rcu_node_kthread(rnp);
 }

My source has this:

        raw_spin_lock_irqsave(&rnp->lock, flags);
        rnp->wakemask |= rdp->grpmask;
        invoke_rcu_node_kthread(rnp);
        raw_spin_unlock_irqrestore(&rnp->lock, flags);

the last 2 lines swapped from what you diffed against. I can easily work around that, except it's unclear what the implications of the invoke_rcu moving outside of the irq save/restore pair (or if it being inside is the actual root cause)...

Paul E. McKenney

2011-05-12 09:47 UTC #7 lore raw

Quoted 30 lines · On Wed, May 11, 2011 at 07:11:34PM -0400, [email protected] wrote:

On Tue, 10 May 2011 01:20:29 PDT, "Paul E. McKenney" said:

Would test, but it doesn't apply cleanly to my -mmotm0506 tree:

Quoted 13 lines

kernel/rcutree.c +2 -1

index 5616b17..20c22c5 100644
@@ -1525,13 +1525,15 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
  */
 static void rcu_cpu_kthread_timer(unsigned long arg)
 {
-	unsigned long flags;
+	unsigned long old;
+	unsigned long new;
 	struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
 	struct rcu_node *rnp = rdp->mynode;

kernel/rcutree.c static void rcu_cpu_kthread_setrt(int cpu, int to_rt) · line 1538

Quoted 10 lines

kernel/rcutree.c +4 -3

 
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->wakemask |= rdp->grpmask;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	do {
+		old = rnp->wakemask;
+		new = old | rdp->grpmask;
+	} while (cmpxchg(&rnp->wakemask, old, new) != old);
 	invoke_rcu_node_kthread(rnp);
 }

My source has this:

Quoted 8 lines

        raw_spin_lock_irqsave(&rnp->lock, flags);
        rnp->wakemask |= rdp->grpmask;
        invoke_rcu_node_kthread(rnp);
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
the last 2 lines swapped from what you diffed against. I can easily work around that, except it's unclear what the implications of the invoke_rcu moving outside of the irq save/restore pair (or if it being inside is the actual root cause)...

Odd...

This looks to me like a recent -next -- I do not believe that straight mmotm has rcu_cpu_kthread_timer() in it. The patch should apply to the last few days' -next kernels.

Thanx, Paul

[email protected]

author

2011-05-12 16:06 UTC #8 lore raw

Quoted 12 lines · Paul E. McKenney

Quoted 10 lines · On Wed, May 11, 2011 at 07:11:34PM -0400, [email protected] wrote:
My source has this:
        raw_spin_lock_irqsave(&rnp->lock, flags);
        rnp->wakemask |= rdp->grpmask;
        invoke_rcu_node_kthread(rnp);
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
the last 2 lines swapped from what you diffed against. I can easily work around that, except it's unclear what the implications of the invoke_rcu moving outside of the irq save/restore pair (or if it being inside is the actual root cause)...

Quoted 5 lines

Odd...
This looks to me like a recent -next -- I do not believe that straight mmotm has rcu_cpu_kthread_timer() in it. The patch should apply to the last few days' -next kernels.

Ah. Found it. Your tree and current linux-next include this commit:

commit 1217ed1ba5c67393293dfb0f03c353b118dadeb4
tree a765356c8418e134de85fd05d9fe6eda41de859c tree | snapshot
parent 29ce831000081dd757d3116bf774aafffc4b6b20 commit | diff
rcu: permit rcu_read_unlock() to be called while holding runqueue locks

which includes this chunk:

@@ -1546,8 +1531,8 @@ static void rcu_cpu_kthread_timer(unsigned long arg)

        raw_spin_lock_irqsave(&rnp->lock, flags);
        rnp->wakemask |= rdp->grpmask;
-       invoke_rcu_node_kthread(rnp);
        raw_spin_unlock_irqrestore(&rnp->lock, flags);

+ invoke_rcu_node_kthread(rnp);
}

but that was committed 4 days ago, and Andrew pulled linux-next for the -mmotm 6 days ago, so it's not in there. The *rest* of your recent commits appear to be in there though. So that explains the patch failure to apply.

Paul E. McKenney

2011-05-13 07:18 UTC #9 lore raw

Quoted 38 lines · On Thu, May 12, 2011 at 12:05:24PM -0400, [email protected] wrote:

Quoted 12 lines · Paul E. McKenney
Quoted 10 lines · On Wed, May 11, 2011 at 07:11:34PM -0400, [email protected] wrote:
My source has this:
        raw_spin_lock_irqsave(&rnp->lock, flags);
        rnp->wakemask |= rdp->grpmask;
        invoke_rcu_node_kthread(rnp);
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
the last 2 lines swapped from what you diffed against. I can easily work around that, except it's unclear what the implications of the invoke_rcu moving outside of the irq save/restore pair (or if it being inside is the actual root cause)...
Quoted 5 lines
Odd...
This looks to me like a recent -next -- I do not believe that straight mmotm has rcu_cpu_kthread_timer() in it. The patch should apply to the last few days' -next kernels.
Ah. Found it. Your tree and current linux-next include this commit:
commit 1217ed1ba5c67393293dfb0f03c353b118dadeb4
tree a765356c8418e134de85fd05d9fe6eda41de859c tree | snapshot
parent 29ce831000081dd757d3116bf774aafffc4b6b20 commit | diff
rcu: permit rcu_read_unlock() to be called while holding runqueue locks
which includes this chunk:
(quoted diff) +1 -1
@@ -1546,8 +1531,8 @@ static void rcu_cpu_kthread_timer(unsigned long arg)
 
        raw_spin_lock_irqsave(&rnp->lock, flags);
        rnp->wakemask |= rdp->grpmask;
-       invoke_rcu_node_kthread(rnp);
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
+       invoke_rcu_node_kthread(rnp);
 }
 
 

Quoted 3 lines

but that was committed 4 days ago, and Andrew pulled linux-next for the -mmotm 6 days ago, so it's not in there. The *rest* of your recent commits appear to be in there though. So that explains the patch failure to apply.

Whew!!! ;-)

Thanx, Paul