Date: Tue, 14 Jul 2015 09:31:54 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Jungseok Lee <jungseoklee85@gmail.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>, catalin.marinas@arm.com,
        will.deacon@arm.com, olof@lixom.net, broonie@kernel.org,
        david.griego@linaro.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC 2/3] arm64: refactor save_stack_trace()
Message-ID: <20150714093154.4d73e551@gandalf.local.home>
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	<1436765375-7119-3-git-send-email-takahiro.akashi@linaro.org>
	<DAAB1BC4-B36E-436D-8EAD-548641E58490@gmail.com>
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On Tue, 14 Jul 2015 21:47:10 +0900
Jungseok Lee <jungseoklee85@gmail.com> wrote:

> Is the below example an unexpected result?
> Entry 17 and 18 are ftrace_call and ftrace_ops_no_ops, respectively.
> 
>         Depth    Size   Location    (51 entries)
>         -----    ----   --------
>   0)     5352      96   _raw_spin_unlock_irqrestore+0x1c/0x60
>   1)     5256      48   gic_raise_softirq+0xa0/0xbc
>   2)     5208      80   smp_cross_call+0x40/0xbc
>   3)     5128      48   smp_send_reschedule+0x38/0x48
>   4)     5080      32   trigger_load_balance+0x184/0x29c
>   5)     5048     112   scheduler_tick+0xac/0x104
>   6)     4936      64   update_process_times+0x5c/0x74
>   7)     4872      32   tick_sched_handle.isra.15+0x38/0x7c
>   8)     4840      48   tick_sched_timer+0x48/0x90
>   9)     4792      48   __run_hrtimer+0x60/0x258
>  10)     4744      64   hrtimer_interrupt+0xe8/0x260
>  11)     4680     128   arch_timer_handler_virt+0x38/0x48
>  12)     4552      32   handle_percpu_devid_irq+0x84/0x188
>  13)     4520      64   generic_handle_irq+0x38/0x54
>  14)     4456      32   __handle_domain_irq+0x68/0xbc
>  15)     4424      64   gic_handle_irq+0x38/0x88
>  16)     4360     280   el1_irq+0x64/0xd8

Note, function tracing does not disable interrupts. This looks to be
that an interrupt came in while __aloc_skb() was being traced.

-- Steve

>  17)     4080     168   ftrace_ops_no_ops+0xb4/0x16c
>  18)     3912      32   ftrace_call+0x0/0x4
>  19)     3880     144   __alloc_skb+0x48/0x180
>  20)     3736      96   alloc_skb_with_frags+0x74/0x234
>  21)     3640     112   sock_alloc_send_pskb+0x1d0/0x294
>  22)     3528     160   sock_alloc_send_skb+0x44/0x54
>  23)     3368      64   __ip_append_data.isra.40+0x78c/0xb48
>  24)     3304     224   ip_append_data.part.42+0x98/0xe8
>  25)     3080     112   ip_append_data+0x68/0x7c
>  26)     2968      96   icmp_push_reply+0x7c/0x144
>  27)     2872      96   icmp_send+0x3c0/0x3c8
>  28)     2776     192   __udp4_lib_rcv+0x5b8/0x684
>  29)     2584      96   udp_rcv+0x2c/0x3c
>  30)     2488      32   ip_local_deliver+0xa0/0x224
>  31)     2456      48   ip_rcv+0x360/0x57c
>  32)     2408      64   __netif_receive_skb_core+0x4d0/0x80c
>  33)     2344     128   __netif_receive_skb+0x24/0x84
>  34)     2216      32   process_backlog+0x9c/0x15c
>  35)     2184      80   net_rx_action+0x1ec/0x32c
>  36)     2104     160   __do_softirq+0x114/0x2f0
>  37)     1944     128   do_softirq+0x60/0x68
>  38)     1816      32   __local_bh_enable_ip+0xb0/0xd4
>  39)     1784      32   ip_finish_output+0x1f4/0xabc
>  40)     1752      96   ip_output+0xf0/0x120
>  41)     1656      64   ip_local_out_sk+0x44/0x54
>  42)     1592      32   ip_send_skb+0x24/0xbc
>  43)     1560      48   udp_send_skb+0x1b4/0x2f4
>  44)     1512      80   udp_sendmsg+0x2a8/0x7a0
>  45)     1432     272   inet_sendmsg+0xa0/0xd0
>  46)     1160      48   sock_sendmsg+0x30/0x78
>  47)     1112      32   ___sys_sendmsg+0x15c/0x26c
>  48)     1080     400   __sys_sendmmsg+0x94/0x180
>  49)      680     320   SyS_sendmmsg+0x38/0x54
>  50)      360     360   el0_svc_naked+0x20/0x28
> 
> Best Regards
> Jungseok Lee

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