Hi all,
While fuzzing using trinity inside a KVM tools guest using the latest
linux-next, I've encountered a hang within the guest. When I've tried dumping
tasks using sysrq-t I got the following:
[ 138.777386] =========================================================
[ 138.777386] [ INFO: possible irq lock inversion dependency detected ]
[ 138.777386] 3.5.0-rc7-next-20120716-sasha-dirty #225 Tainted: G W
[ 138.777386] ---------------------------------------------------------
[ 138.777386] swapper/0/0 just changed the state of lock:
[ 138.777386] (tasklist_lock){.?.+..}, at: [<ffffffff8113f833>]
print_rq+0x53/0x190
[ 138.777386] but this lock took another, HARDIRQ-unsafe lock in the past:
[ 138.777386] (&(&p->alloc_lock)->rlock){+.+...}
and interrupts could create inverse lock ordering between them.
[ 138.777386]
[ 138.777386] other info that might help us debug this:
[ 138.777386] Possible interrupt unsafe locking scenario:
[ 138.777386]
[ 138.777386] CPU0 CPU1
[ 138.777386] ---- ----
[ 138.777386] lock(&(&p->alloc_lock)->rlock);
[ 138.777386] local_irq_disable();
[ 138.777386] lock(tasklist_lock);
[ 138.777386] lock(&(&p->alloc_lock)->rlock);
[ 138.777386] <Interrupt>
[ 138.777386] lock(tasklist_lock);
[ 138.777386]
[ 138.777386] *** DEADLOCK ***
[ 138.777386]
[ 138.777386] 6 locks held by swapper/0/0:
[ 138.777386] #0: (&(&i->lock)->rlock){-.-...}, at: [<ffffffff81b5a09c>]
serial8250_interrupt+0x2c/0xd0
[ 138.777386] #1: (&port_lock_key){-.-...}, at: [<ffffffff81b5b1f3>]
serial8250_handle_irq+0x23/0x80
[ 138.777386] #2: (sysrq_key_table_lock){-.....}, at: [<ffffffff81b3eead>]
__handle_sysrq+0x2d/0x180
[ 138.777386] #3: (rcu_read_lock){.+.+..}, at: [<ffffffff8112f2a0>]
show_state_filter+0x0/0x220
[ 138.777386] #4: (sched_debug_lock){-.....}, at: [<ffffffff8113ff6c>]
print_cpu+0x5fc/0x710
[ 138.777386] #5: (rcu_read_lock){.+.+..}, at: [<ffffffff8113ff60>]
print_cpu+0x5f0/0x710
[ 138.777386]
[ 138.777386] the shortest dependencies between 2nd lock and 1st lock:
[ 138.777386] -> (&(&p->alloc_lock)->rlock){+.+...} ops: 83940 {
[ 138.777386] HARDIRQ-ON-W at:
[ 138.777386] [<ffffffff8115cd10>]
mark_irqflags+0x100/0x190
[ 138.777386] [<ffffffff8115eefb>]
__lock_acquire+0x92b/0xb50
[ 138.777386] [<ffffffff8116158a>]
lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8377fb1b>]
_raw_spin_lock+0x3b/0x70
[ 138.777386] [<ffffffff81258681>]
set_task_comm+0x31/0x1c0
[ 138.777386] [<ffffffff8111836c>] kthreadd+0x2c/0x170
[ 138.777386] [<ffffffff83782c74>]
kernel_thread_helper+0x4/0x10
[ 138.777386] SOFTIRQ-ON-W at:
[ 138.777386] [<ffffffff8115cd33>]
mark_irqflags+0x123/0x190
[ 138.777386] [<ffffffff8115eefb>]
__lock_acquire+0x92b/0xb50
[ 138.777386] [<ffffffff8116158a>]
lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8377fb1b>]
_raw_spin_lock+0x3b/0x70
[ 138.777386] [<ffffffff81258681>]
set_task_comm+0x31/0x1c0
[ 138.777386] [<ffffffff8111836c>] kthreadd+0x2c/0x170
[ 138.777386] [<ffffffff83782c74>]
kernel_thread_helper+0x4/0x10
[ 138.777386] INITIAL USE at:
[ 138.777386] [<ffffffff8115ef24>]
__lock_acquire+0x954/0xb50
[ 138.777386] [<ffffffff8116158a>]
lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8377fb1b>]
_raw_spin_lock+0x3b/0x70
[ 138.777386] [<ffffffff81258681>]
set_task_comm+0x31/0x1c0
[ 138.777386] [<ffffffff8111836c>] kthreadd+0x2c/0x170
[ 138.777386] [<ffffffff83782c74>]
kernel_thread_helper+0x4/0x10
[ 138.777386] }
[ 138.777386] ... key at: [<ffffffff85352228>] __key.45660+0x0/0x8
[ 138.777386] ... acquired at:
[ 138.777386] [<ffffffff8115beba>] check_prevs_add+0xba/0x1a0
[ 138.777386] [<ffffffff8115c640>] validate_chain.isra.22+0x6a0/0x7b0
[ 138.777386] [<ffffffff8115f05d>] __lock_acquire+0xa8d/0xb50
[ 138.777386] [<ffffffff8116158a>] lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8377fb1b>] _raw_spin_lock+0x3b/0x70
[ 138.777386] [<ffffffff818bea25>] keyctl_session_to_parent+0x105/0x3f0
[ 138.777386] [<ffffffff818bee65>] sys_keyctl+0x155/0x1a0
[ 138.777386] [<ffffffff8378163d>] system_call_fastpath+0x1a/0x1f
[ 138.777386]
[ 138.777386] -> (tasklist_lock){.?.+..} ops: 31775 {
[ 138.777386] IN-HARDIRQ-R at:
[ 138.777386] [<ffffffff8115cc51>] mark_irqflags+0x41/0x190
[ 138.777386] [<ffffffff8115eefb>]
__lock_acquire+0x92b/0xb50
[ 138.777386] [<ffffffff8116158a>] lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8378006c>]
_raw_read_lock_irqsave+0x7c/0xc0
[ 138.777386] [<ffffffff8113f833>] print_rq+0x53/0x190
[ 138.777386] [<ffffffff8113fffe>] print_cpu+0x68e/0x710
[ 138.777386] [<ffffffff81140702>]
sched_debug_show+0x682/0x720
[ 138.777386] [<ffffffff8114129d>]
sysrq_sched_debug_show+0xd/0x10
[ 138.777386] [<ffffffff8112f43e>]
show_state_filter+0x19e/0x220
[ 138.777386] [<ffffffff81b3eb5b>]
sysrq_handle_showstate+0xb/0x10
[ 138.777386] [<ffffffff81b3ef37>]
__handle_sysrq+0xb7/0x180
[ 138.777386] [<ffffffff81b3f221>] handle_sysrq+0x21/0x30
[ 138.777386] [<ffffffff81b5ab49>]
serial8250_rx_chars+0x189/0x220
[ 138.777386] [<ffffffff81b5b216>]
serial8250_handle_irq+0x46/0x80
[ 138.777386] [<ffffffff81b5b26e>]
serial8250_default_handle_irq+0x1e/0x30
[ 138.777386] [<ffffffff81b5a0be>]
serial8250_interrupt+0x4e/0xd0
[ 138.777386] [<ffffffff81196ad9>]
handle_irq_event_percpu+0x139/0x420
[ 138.777386] [<ffffffff81196e03>]
handle_irq_event+0x43/0x70
[ 138.777386] [<ffffffff81199b88>]
handle_level_irq+0x98/0xe0
[ 138.777386] [<ffffffff8106d374>] handle_irq+0x164/0x190
[ 138.777386] [<ffffffff8106cec5>] do_IRQ+0x55/0xd0
[ 138.777386] [<ffffffff83780caf>] ret_from_intr+0x0/0x1a
[ 138.777386] [<ffffffff81074a65>] default_idle+0x235/0x5c0
[ 138.777386] [<ffffffff81076648>] cpu_idle+0x118/0x160
[ 138.777386] [<ffffffff835d3d6c>] rest_init+0x130/0x144
[ 138.777386] [<ffffffff850efc3e>] start_kernel+0x392/0x39f
[ 138.777386] [<ffffffff850ef397>]
x86_64_start_reservations+0x101/0x105
[ 138.777386] [<ffffffff850ef480>]
x86_64_start_kernel+0xe5/0xf4
[ 138.777386] HARDIRQ-ON-R at:
[ 138.777386] [<ffffffff8115ccdc>] mark_irqflags+0xcc/0x190
[ 138.777386] [<ffffffff8115eefb>]
__lock_acquire+0x92b/0xb50
[ 138.777386] [<ffffffff8116158a>] lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8377ffae>] _raw_read_lock+0x3e/0x80
[ 138.777386] [<ffffffff810ef898>] do_wait+0x178/0x3b0
[ 138.777386] [<ffffffff810f10cb>] sys_wait4+0xbb/0xe0
[ 138.777386] [<ffffffff81109c30>]
wait_for_helper+0x80/0xa0
[ 138.777386] [<ffffffff83782c74>]
kernel_thread_helper+0x4/0x10
[ 138.777386] SOFTIRQ-ON-R at:
[ 138.777386] [<ffffffff8115cd33>]
mark_irqflags+0x123/0x190
[ 138.777386] [<ffffffff8115eefb>]
__lock_acquire+0x92b/0xb50
[ 138.777386] [<ffffffff8116158a>] lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8377ffae>] _raw_read_lock+0x3e/0x80
[ 138.777386] [<ffffffff810ef898>] do_wait+0x178/0x3b0
[ 138.777386] [<ffffffff810f10cb>] sys_wait4+0xbb/0xe0
[ 138.777386] [<ffffffff81109c30>]
wait_for_helper+0x80/0xa0
[ 138.777386] [<ffffffff83782c74>]
kernel_thread_helper+0x4/0x10
[ 138.777386] INITIAL USE at:
[ 138.777386] [<ffffffff8115ef24>]
__lock_acquire+0x954/0xb50
[ 138.777386] [<ffffffff8116158a>] lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff837805a9>]
_raw_write_lock_irq+0x59/0x90
[ 138.777386] [<ffffffff810e8015>] copy_process+0xb25/0x11c0
[ 138.777386] [<ffffffff810e87f4>] do_fork+0x104/0x3d0
[ 138.777386] [<ffffffff81076451>] kernel_thread+0x71/0x80
[ 138.777386] [<ffffffff835d3c5d>] rest_init+0x21/0x144
[ 138.777386] [<ffffffff850efc3e>] start_kernel+0x392/0x39f
[ 138.777386] [<ffffffff850ef397>]
x86_64_start_reservations+0x101/0x105
[ 138.777386] [<ffffffff850ef480>]
x86_64_start_kernel+0xe5/0xf4
[ 138.777386] }
[ 138.777386] ... key at: [<ffffffff8481e018>] tasklist_lock+0x18/0x80
[ 138.777386] ... acquired at:
[ 138.777386] [<ffffffff8115b0e1>] check_usage_forwards+0xe1/0x100
[ 138.777386] [<ffffffff836c8351>] mark_lock_irq+0x91/0x137
[ 138.777386] [<ffffffff8115cb3b>] mark_lock+0x10b/0x1e0
[ 138.777386] [<ffffffff8115cc51>] mark_irqflags+0x41/0x190
[ 138.777386] [<ffffffff8115eefb>] __lock_acquire+0x92b/0xb50
[ 138.777386] [<ffffffff8116158a>] lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8378006c>] _raw_read_lock_irqsave+0x7c/0xc0
[ 138.777386] [<ffffffff8113f833>] print_rq+0x53/0x190
[ 138.777386] [<ffffffff8113fffe>] print_cpu+0x68e/0x710
[ 138.777386] [<ffffffff81140702>] sched_debug_show+0x682/0x720
[ 138.777386] [<ffffffff8114129d>] sysrq_sched_debug_show+0xd/0x10
[ 138.777386] [<ffffffff8112f43e>] show_state_filter+0x19e/0x220
[ 138.777386] [<ffffffff81b3eb5b>] sysrq_handle_showstate+0xb/0x10
[ 138.777386] [<ffffffff81b3ef37>] __handle_sysrq+0xb7/0x180
[ 138.777386] [<ffffffff81b3f221>] handle_sysrq+0x21/0x30
[ 138.777386] [<ffffffff81b5ab49>] serial8250_rx_chars+0x189/0x220
[ 138.777386] [<ffffffff81b5b216>] serial8250_handle_irq+0x46/0x80
[ 138.777386] [<ffffffff81b5b26e>] serial8250_default_handle_irq+0x1e/0x30
[ 138.777386] [<ffffffff81b5a0be>] serial8250_interrupt+0x4e/0xd0
[ 138.777386] [<ffffffff81196ad9>] handle_irq_event_percpu+0x139/0x420
[ 138.777386] [<ffffffff81196e03>] handle_irq_event+0x43/0x70
[ 138.777386] [<ffffffff81199b88>] handle_level_irq+0x98/0xe0
[ 138.777386] [<ffffffff8106d374>] handle_irq+0x164/0x190
[ 138.777386] [<ffffffff8106cec5>] do_IRQ+0x55/0xd0
[ 138.777386] [<ffffffff83780caf>] ret_from_intr+0x0/0x1a
[ 138.777386] [<ffffffff81074a65>] default_idle+0x235/0x5c0
[ 138.777386] [<ffffffff81076648>] cpu_idle+0x118/0x160
[ 138.777386] [<ffffffff835d3d6c>] rest_init+0x130/0x144
[ 138.777386] [<ffffffff850efc3e>] start_kernel+0x392/0x39f
[ 138.777386] [<ffffffff850ef397>] x86_64_start_reservations+0x101/0x105
[ 138.777386] [<ffffffff850ef480>] x86_64_start_kernel+0xe5/0xf4
[ 138.777386]
[ 138.777386]
[ 138.777386] stack backtrace:
[ 138.777386] Pid: 0, comm: swapper/0 Tainted: G W
3.5.0-rc7-next-20120716-sasha-dirty #225
[ 138.777386] Call Trace:
[ 138.777386] <IRQ> [<ffffffff8115afdf>] print_irq_inversion_bug+0x1ff/0x220
[ 138.777386] [<ffffffff8115b0e1>] check_usage_forwards+0xe1/0x100
[ 138.777386] [<ffffffff8106d758>] ? dump_trace+0x1f8/0x230
[ 138.777386] [<ffffffff8115b000>] ? print_irq_inversion_bug+0x220/0x220
[ 138.777386] [<ffffffff836c8351>] mark_lock_irq+0x91/0x137
[ 138.777386] [<ffffffff8115cb3b>] mark_lock+0x10b/0x1e0
[ 138.777386] [<ffffffff8115cc51>] mark_irqflags+0x41/0x190
[ 138.777386] [<ffffffff8115eefb>] __lock_acquire+0x92b/0xb50
[ 138.777386] [<ffffffff81999038>] ? do_raw_spin_unlock+0xc8/0xe0
[ 138.777386] [<ffffffff8377fdfc>] ? _raw_spin_unlock_irqrestore+0x7c/0xa0
[ 138.777386] [<ffffffff810eb391>] ? console_unlock+0x3a1/0x3e0
[ 138.777386] [<ffffffff8116158a>] lock_acquire+0x1ca/0x270
[ 138.777386] [<ffffffff8113f833>] ? print_rq+0x53/0x190
[ 138.777386] [<ffffffff8378006c>] _raw_read_lock_irqsave+0x7c/0xc0
[ 138.777386] [<ffffffff8113f833>] ? print_rq+0x53/0x190
[ 138.777386] [<ffffffff8113f833>] print_rq+0x53/0x190
[ 138.777386] [<ffffffff8113fffe>] print_cpu+0x68e/0x710
[ 138.777386] [<ffffffff8113ff60>] ? print_cpu+0x5f0/0x710
[ 138.777386] [<ffffffff81140702>] sched_debug_show+0x682/0x720
[ 138.777386] [<ffffffff8114129d>] sysrq_sched_debug_show+0xd/0x10
[ 138.777386] [<ffffffff8112f43e>] show_state_filter+0x19e/0x220
[ 138.777386] [<ffffffff8112f2a0>] ? sched_show_task+0x1a0/0x1a0
[ 138.777386] [<ffffffff81b3eead>] ? __handle_sysrq+0x2d/0x180
[ 138.777386] [<ffffffff81b3eb5b>] sysrq_handle_showstate+0xb/0x10
[ 138.777386] [<ffffffff81b3ef37>] __handle_sysrq+0xb7/0x180
[ 138.777386] [<ffffffff81b3f221>] handle_sysrq+0x21/0x30
[ 138.777386] [<ffffffff81b5ab49>] serial8250_rx_chars+0x189/0x220
[ 138.777386] [<ffffffff8377fbf5>] ? _raw_spin_lock_irqsave+0xa5/0xc0
[ 138.777386] [<ffffffff81b5b1f3>] ? serial8250_handle_irq+0x23/0x80
[ 138.777386] [<ffffffff81b5b216>] serial8250_handle_irq+0x46/0x80
[ 138.777386] [<ffffffff81b5b26e>] serial8250_default_handle_irq+0x1e/0x30
[ 138.777386] [<ffffffff81b5a0be>] serial8250_interrupt+0x4e/0xd0
[ 138.777386] [<ffffffff81196df8>] ? handle_irq_event+0x38/0x70
[ 138.777386] [<ffffffff81196ad9>] handle_irq_event_percpu+0x139/0x420
[ 138.777386] [<ffffffff81196e03>] handle_irq_event+0x43/0x70
[ 138.777386] [<ffffffff81199b09>] ? handle_level_irq+0x19/0xe0
[ 138.777386] [<ffffffff81199b88>] handle_level_irq+0x98/0xe0
[ 138.777386] [<ffffffff8106d374>] handle_irq+0x164/0x190
[ 138.777386] [<ffffffff8106cec5>] do_IRQ+0x55/0xd0
[ 138.777386] [<ffffffff83780caf>] common_interrupt+0x6f/0x6f
[ 138.777386] <EOI> [<ffffffff8109e036>] ? native_safe_halt+0x6/0x10
[ 138.777386] [<ffffffff8115d17d>] ? trace_hardirqs_on+0xd/0x10
[ 138.777386] [<ffffffff81074a65>] default_idle+0x235/0x5c0
[ 138.777386] [<ffffffff81076648>] cpu_idle+0x118/0x160
[ 138.777386] [<ffffffff835d3d6c>] rest_init+0x130/0x144
[ 138.777386] [<ffffffff835d3c3c>] ? csum_partial_copy_generic+0x16c/0x16c
[ 138.777386] [<ffffffff850efc3e>] start_kernel+0x392/0x39f
[ 138.777386] [<ffffffff850ef6b7>] ? obsolete_checksetup+0xaf/0xaf
[ 138.777386] [<ffffffff850ef397>] x86_64_start_reservations+0x101/0x105
[ 138.777386] [<ffffffff850ef120>] ? early_idt_handlers+0x120/0x120
[ 138.777386] [<ffffffff850ef480>] x86_64_start_kernel+0xe5/0xf4
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