xfrm_state lock protects its state, i.e., VALID/DEAD and statistics,
not the transforming procedure, as both mode/type output functions
are reentrant.

Another issue is state lock can be used in BH context when state timer
alarmed, after transformation in pktgen, update state statistics acquiring
state lock should disabled BH context for a moment. Otherwise LOCKDEP
critisize this:

[   62.354339] pktgen: Packet Generator for packet performance testing. Version: 2.74
[   62.655444]
[   62.655448] =================================
[   62.655451] [ INFO: inconsistent lock state ]
[   62.655455] 3.13.0-rc2+ #70 Not tainted
[   62.655457] ---------------------------------
[   62.655459] inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
[   62.655463] kpktgend_0/2764 [HC0[0]:SC0[0]:HE1:SE1] takes:
[   62.655466]  (&(&x->lock)->rlock){+.?...}, at: [<ffffffffa00886f6>] pktgen_thread_worker+0x1796/0x1860 [pktgen]
[   62.655479] {IN-SOFTIRQ-W} state was registered at:
[   62.655484]   [<ffffffff8109a61d>] __lock_acquire+0x62d/0x1d70
[   62.655492]   [<ffffffff8109c3c7>] lock_acquire+0x97/0x130
[   62.655498]   [<ffffffff81774af6>] _raw_spin_lock+0x36/0x70
[   62.655505]   [<ffffffff816dc3a3>] xfrm_timer_handler+0x43/0x290
[   62.655511]   [<ffffffff81059437>] __tasklet_hrtimer_trampoline+0x17/0x40
[   62.655519]   [<ffffffff8105a1b7>] tasklet_hi_action+0xd7/0xf0
[   62.655523]   [<ffffffff81059ac6>] __do_softirq+0xe6/0x2d0
[   62.655526]   [<ffffffff8105a026>] irq_exit+0x96/0xc0
[   62.655530]   [<ffffffff8177fd0a>] smp_apic_timer_interrupt+0x4a/0x60
[   62.655537]   [<ffffffff8177e96f>] apic_timer_interrupt+0x6f/0x80
[   62.655541]   [<ffffffff8100b7c6>] arch_cpu_idle+0x26/0x30
[   62.655547]   [<ffffffff810ace28>] cpu_startup_entry+0x88/0x2b0
[   62.655552]   [<ffffffff81761c3c>] rest_init+0xbc/0xd0
[   62.655557]   [<ffffffff81ea5e5e>] start_kernel+0x3c4/0x3d1
[   62.655583]   [<ffffffff81ea55a8>] x86_64_start_reservations+0x2a/0x2c
[   62.655588]   [<ffffffff81ea569f>] x86_64_start_kernel+0xf5/0xfc
[   62.655592] irq event stamp: 77
[   62.655594] hardirqs last  enabled at (77): [<ffffffff810ab7f2>] vprintk_emit+0x1b2/0x520
[   62.655597] hardirqs last disabled at (76): [<ffffffff810ab684>] vprintk_emit+0x44/0x520
[   62.655601] softirqs last  enabled at (22): [<ffffffff81059b57>] __do_softirq+0x177/0x2d0
[   62.655605] softirqs last disabled at (15): [<ffffffff8105a026>] irq_exit+0x96/0xc0
[   62.655609]
[   62.655609] other info that might help us debug this:
[   62.655613]  Possible unsafe locking scenario:
[   62.655613]
[   62.655616]        CPU0
[   62.655617]        ----
[   62.655618]   lock(&(&x->lock)->rlock);
[   62.655622]   <Interrupt>
[   62.655623]     lock(&(&x->lock)->rlock);
[   62.655626]
[   62.655626]  *** DEADLOCK ***
[   62.655626]
[   62.655629] no locks held by kpktgend_0/2764.
[   62.655631]
[   62.655631] stack backtrace:
[   62.655636] CPU: 0 PID: 2764 Comm: kpktgend_0 Not tainted 3.13.0-rc2+ #70
[   62.655638] Hardware name: innotek GmbH VirtualBox, BIOS VirtualBox 12/01/2006
[   62.655642]  ffffffff8216b7b0 ffff88001be43ab8 ffffffff8176af37 0000000000000007
[   62.655652]  ffff88001c8d4fc0 ffff88001be43b18 ffffffff81766d78 0000000000000000
[   62.655663]  ffff880000000001 ffff880000000001 ffffffff8101025f ffff88001be43b18
[   62.655671] Call Trace:
[   62.655680]  [<ffffffff8176af37>] dump_stack+0x46/0x58
[   62.655685]  [<ffffffff81766d78>] print_usage_bug+0x1f1/0x202
[   62.655691]  [<ffffffff8101025f>] ? save_stack_trace+0x2f/0x50
[   62.655696]  [<ffffffff81099f8c>] mark_lock+0x28c/0x2f0
[   62.655700]  [<ffffffff810994b0>] ? check_usage_forwards+0x150/0x150
[   62.655704]  [<ffffffff8109a67a>] __lock_acquire+0x68a/0x1d70
[   62.655712]  [<ffffffff81115b09>] ? irq_work_queue+0x69/0xb0
[   62.655717]  [<ffffffff810ab7f2>] ? vprintk_emit+0x1b2/0x520
[   62.655722]  [<ffffffff8109cec5>] ? trace_hardirqs_on_caller+0x105/0x1d0
[   62.655730]  [<ffffffffa00886f6>] ? pktgen_thread_worker+0x1796/0x1860 [pktgen]
[   62.655734]  [<ffffffff8109c3c7>] lock_acquire+0x97/0x130
[   62.655741]  [<ffffffffa00886f6>] ? pktgen_thread_worker+0x1796/0x1860 [pktgen]
[   62.655745]  [<ffffffff81774af6>] _raw_spin_lock+0x36/0x70
[   62.655752]  [<ffffffffa00886f6>] ? pktgen_thread_worker+0x1796/0x1860 [pktgen]
[   62.655758]  [<ffffffffa00886f6>] pktgen_thread_worker+0x1796/0x1860 [pktgen]
[   62.655766]  [<ffffffffa0087a79>] ? pktgen_thread_worker+0xb19/0x1860 [pktgen]
[   62.655771]  [<ffffffff8109cf9d>] ? trace_hardirqs_on+0xd/0x10
[   62.655777]  [<ffffffff81775410>] ? _raw_spin_unlock_irq+0x30/0x40
[   62.655785]  [<ffffffff8151faa0>] ? e1000_clean+0x9d0/0x9d0
[   62.655791]  [<ffffffff81094310>] ? __init_waitqueue_head+0x60/0x60
[   62.655795]  [<ffffffff81094310>] ? __init_waitqueue_head+0x60/0x60
[   62.655800]  [<ffffffffa0086f60>] ? mod_cur_headers+0x7f0/0x7f0 [pktgen]
[   62.655806]  [<ffffffff81078f84>] kthread+0xe4/0x100
[   62.655813]  [<ffffffff81078ea0>] ? flush_kthread_worker+0x170/0x170
[   62.655819]  [<ffffffff8177dc6c>] ret_from_fork+0x7c/0xb0
[   62.655824]  [<ffffffff81078ea0>] ? flush_kthread_worker+0x170/0x170

Signed-off-by: Fan Du <fan.du@windriver.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>