Re: [2.6.29-git12] BUG: scheduling while atomic: swapper/0/0x10000100

Thomas Gleixner
2009-04-10T18:27:07Z

Maciej,

On Fri, 10 Apr 2009, Maciej Rutecki wrote:
> 2009/4/10 Thomas Gleixner <tglx@linutronix.de>:
>
> [...]
> > Please upload trace.bz2 file to some place.
>
> http://unixy.pl/maciek/download/kernel/2.6.30-rc1-git3/laptop/trace-2.6.30-rc1-git3.bz2

Ok. That gives us the necessary information:

<idle>-0 1d... 76597263us : do_softirq <-irq_exit
<idle>-0 1d... 76597263us : __do_softirq <-do_softirq
<idle>-0 1..s. 76597264us : tasklet_action <-__do_softirq
<idle>-0 1..s. 76597265us : hci_rx_task <-tasklet_action
<idle>-0 1..s. 76597266us : _read_lock <-hci_rx_task
<idle>-0 1..s. 76597267us : skb_dequeue <-hci_rx_task
<idle>-0 1..s. 76597268us : _spin_lock_irqsave <-skb_dequeue
<idle>-0 1d.s. 76597269us : _spin_unlock_irqrestore <-skb_dequeue
<idle>-0 1..s. 76597270us : hci_send_to_sock <-hci_rx_task
<idle>-0 1..s. 76597270us+: _read_lock <-hci_send_to_sock
<idle>-0 1..s. 76597272us : skb_clone <-hci_send_to_sock
<idle>-0 1..s. 76597273us : kmem_cache_alloc <-skb_clone
<idle>-0 1..s. 76597274us : __skb_clone <-skb_clone
<idle>-0 1..s. 76597275us : __copy_skb_header <-__skb_clone
<idle>-0 1..s. 76597276us : skb_push <-hci_send_to_sock
<idle>-0 1..s. 76597277us : sock_queue_rcv_skb <-hci_send_to_sock
<idle>-0 1..s. 76597278us : sk_filter <-sock_queue_rcv_skb
<idle>-0 1..s. 76597279us : security_sock_rcv_skb <-sk_filter
<idle>-0 1..s. 76597280us : cap_socket_sock_rcv_skb <-security_sock_rcv_skb
<idle>-0 1..s. 76597280us : local_bh_disable <-sk_filter
<idle>-0 1..s. 76597281us : local_bh_enable <-sk_filter
<idle>-0 1..s. 76597282us : skb_queue_tail <-sock_queue_rcv_skb
<idle>-0 1..s. 76597283us : _spin_lock_irqsave <-skb_queue_tail
<idle>-0 1d.s. 76597284us : _spin_unlock_irqrestore <-skb_queue_tail
<idle>-0 1..s. 76597285us : sock_def_readable <-sock_queue_rcv_skb
<idle>-0 1..s. 76597286us : _read_lock <-sock_def_readable
<idle>-0 1..s. 76597286us : __wake_up_sync_key <-sock_def_readable
<idle>-0 1..s. 76597287us : _spin_lock_irqsave <-__wake_up_sync_key
<idle>-0 1d.s. 76597288us : __wake_up_common <-__wake_up_sync_key
<idle>-0 1d.s. 76597289us : pollwake <-__wake_up_common
<idle>-0 1d.s. 76597290us : default_wake_function <-pollwake
<idle>-0 1d.s. 76597290us : try_to_wake_up <-default_wake_function
<idle>-0 1d.s. 76597292us : update_shares <-try_to_wake_up
<idle>-0 1d.s. 76597293us : walk_tg_tree <-update_shares
<idle>-0 1d.s. 76597294us : tg_nop <-walk_tg_tree
<idle>-0 1d.s. 76597294us : tg_nop <-walk_tg_tree
<idle>-0 1d.s. 76597295us : tg_shares_up <-walk_tg_tree
<idle>-0 1d.s. 76597297us : tg_nop <-walk_tg_tree
<idle>-0 1d.s. 76597297us : tg_shares_up <-walk_tg_tree
<idle>-0 1d.s. 76597298us : tg_nop <-walk_tg_tree
<idle>-0 1d.s. 76597299us : tg_shares_up <-walk_tg_tree
<idle>-0 1d.s. 76597300us : tg_nop <-walk_tg_tree
<idle>-0 1d.s. 76597301us : tg_shares_up <-walk_tg_tree
<idle>-0 1d.s. 76597302us : tg_nop <-walk_tg_tree
<idle>-0 1d.s. 76597303us : tg_shares_up <-walk_tg_tree
<idle>-0 1d.s. 76597304us : tg_shares_up <-walk_tg_tree
<idle>-0 1d.s. 76597305us+: task_rq_lock <-try_to_wake_up
<idle>-0 1d.s. 76597314us : _spin_lock <-task_rq_lock
<idle>-0 1d.s. 76597315us : select_task_rq_fair <-try_to_wake_up
<idle>-0 1d.s. 76597316us : activate_task <-try_to_wake_up
<idle>-0 1d.s. 76597317us : enqueue_task_fair <-activate_task
<idle>-0 1d.s. 76597317us : enqueue_entity <-enqueue_task_fair
<idle>-0 1d.s. 76597318us : update_curr <-enqueue_entity
<idle>-0 1d.s. 76597319us : place_entity <-enqueue_entity
<idle>-0 1d.s. 76597320us : enqueue_entity <-enqueue_task_fair
<idle>-0 1d.s. 76597321us : update_curr <-enqueue_entity
<idle>-0 1d.s. 76597321us : place_entity <-enqueue_entity
<idle>-0 1d.s. 76597322us : check_preempt_curr_idle <-try_to_wake_up
<idle>-0 1d.s. 76597323us : resched_task <-check_preempt_curr_idle
<idle>-0 1dNs. 76597324us : _spin_unlock_irqrestore <-try_to_wake_up
<idle>-0 1dNs. 76597325us+: _spin_unlock_irqrestore <-__wake_up_sync_key
<idle>-0 1.Ns. 76597326us : hci_event_packet <-hci_rx_task
<idle>-0 1.Ns. 76597327us : skb_pull <-hci_event_packet
<idle>-0 1.Ns. 76597328us : _spin_lock <-hci_event_packet
<idle>-0 1.Ns. 76597330us : del_timer <-hci_event_packet
<idle>-0 1.Ns. 76597331us : hci_conn_add_sysfs <-hci_event_packet
<idle>-0 1.Ns. 76597332us+: dev_set_name <-hci_conn_add_sysfs

Here we call dev_set_name from tasklet context which in turn calls kmalloc.

<idle>-0 1.Ns. 76597334us+: strnlen <-string
<idle>-0 1.Ns. 76597336us : __kmalloc <-kvasprintf
<idle>-0 1.Ns. 76597337us : get_slab <-__kmalloc
<idle>-0 1.Ns. 76597338us : _cond_resched <-__kmalloc

We woke up a task above so the resched bit is set and we schedule
out from the softirq context. Bad idea :)

<idle>-0 1.Ns. 76597338us : __cond_resched <-_cond_resched
<idle>-0 1.Ns. 76597339us : schedule <-__cond_resched
<idle>-0 1.Ns. 76597340us : __schedule <-schedule
<idle>-0 1.Ns. 76597341us : rcu_qsctr_inc <-__schedule
<idle>-0 1.Ns. 76597342us : __schedule_bug <-__schedule

Marcel, can you please have a look at that ?

Thanks,

tglx