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SubjectRe: Crash in msm serial on dragonboard with ftrace bootargs
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Date
On 10/16/2018 8:59 PM, Steven Rostedt wrote:
> On Tue, 16 Oct 2018 17:08:25 +0530
> Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> wrote:
>
>> Hi,
>>
>> On dragonboard 410c, with "ftrace=function" boot args, the console
>> output slows down and board resets without any backtrace as below. This
>> is tested on latest kernel and seems to exist even in older kernels as well.
>
> So this only happens when ftrace=function is on the boot console.
>

Yes. If I do not use boot console, target does not crash.

>
>>
>> [ 2.949164] EINJ: ACPI disabled.
>> [ 3.133001] Serial: 8250/16550 dri
>> Format: Log Type - Time(microsec) - Message - Optional Info
>> Log Type: B - Since Boot(Power On Reset), D - Delta, S - Statistic
>>
>> But with pstore enabled, able to get the below backtrace:
>>
>> <4>[ 2.949164] EINJ: ACPI disabled.
>> <6>[ 3.133001] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
>> <6>[ 3.164097] SuperH (H)SCI(F) driver initialized
>> <0>[ 3.164471] Internal error: synchronous external abort: 96000010
>> [#1] PREEMPT SMP
>> <4>[ 3.164479] Modules linked in:
>> <4>[ 3.164495] CPU: 2 PID: 1 Comm: swapper/0 Not tainted
>> 4.19.0-rc8-00008-ge033b9909fff-dirty #175
>> <4>[ 3.164501] Hardware name: Qualcomm Technologies, Inc. APQ 8016
>> SBC (DT)
>> <4>[ 3.164508] pstate: 40000085 (nZcv daIf -PAN -UAO)
>> <4>[ 3.164514] pc : msm_read.isra.2+0x20/0x50
>> <4>[ 3.164520] lr : msm_read.isra.2+0x1c/0x50
>> <4>[ 3.164526] sp : ffff000008033a50
>> <4>[ 3.164531] x29: ffff000008033a50 x28: ffff000009486018
>> <4>[ 3.164548] x27: 0000000000000001 x26: ffff7dfffe7ff070
>> <4>[ 3.164565] x25: 0000000000000034 x24: ffff000009486000
>> <4>[ 3.164582] x23: 0000000000000000 x22: ffff00000978e190
>> <4>[ 3.164599] x21: ffff0000095e8228 x20: 0000000000000034
>> <4>[ 3.164616] x19: ffff7dfffe7ff008 x18: ffffffffffffffff
>> <4>[ 3.164632] x17: 0000000000000000 x16: 0000000000000000
>> <4>[ 3.164649] x15: ffff0000094a96c8 x14: ffff00008978e6bf
>> <4>[ 3.164666] x13: ffff00000978e6cd x12: 0000000000000038
>> <4>[ 3.164683] x11: ffff0000094c6000 x10: 0000000000000c24
>> <4>[ 3.164699] x9 : ffff80003c89b400 x8 : ffff000008033970
>> <4>[ 3.164716] x7 : ffff80000eb04100 x6 : 00000000000af304
>> <4>[ 3.164732] x5 : 0000000000000c40 x4 : ffff80003c06f000
>> <4>[ 3.164750] x3 : ffff80003c89b498 x2 : 0000000000000000
>> <4>[ 3.164766] x1 : ffff80003ca68000 x0 : 0000000000000800
>> <0>[ 3.164785] Process swapper/0 (pid: 1, stack limit =
>> 0x(____ptrval____))
>> <4>[ 3.164791] Call trace:
>> <4>[ 3.164797] msm_read.isra.2+0x20/0x50
>> <4>[ 3.164804] msm_reset_dm_count+0x44/0x80
>> <4>[ 3.164810] __msm_console_write+0x1c8/0x1d0
>> <4>[ 3.164816] msm_serial_early_write_dm+0x3c/0x50
>> <4>[ 3.164823] console_unlock.part.6+0x468/0x528
>> <4>[ 3.164829] vprintk_emit+0x210/0x218
>> <4>[ 3.164835] vprintk_default+0x48/0x58
>> <4>[ 3.164841] vprintk_func+0xf0/0x1c0
>> <4>[ 3.164847] printk+0x74/0x94
>> <4>[ 3.164853] sci_init+0x24/0x3c
>> <4>[ 3.164859] do_one_initcall+0x54/0x248
>> <4>[ 3.164866] kernel_init_freeable+0x210/0x378
>> <4>[ 3.164872] kernel_init+0x18/0x118
>> <4>[ 3.164878] ret_from_fork+0x10/0x1c
>> <0>[ 3.164884] Code: aa1e03e0 8b214273 97e616f7 d503201f (b9400260)
>>
>> Seems to be issue with the msm serial driver and not ftrace.
>> Could someone look into it.
>
> I'm guessing that there may have been an issue with ftrace, it tried to
> print, but the printing caused a bug that rebooted the box.
>
> Does function tracing work after boot up? That is, without the
> ftrace=function, can you do:
>
> echo function > /sys/kernel/debug/tracing/current_tracer
>
> without any issue?
>

Yes ftrace in general works without any issue. I have also tested on
db820c and sdm845 where "ftrace=function" works fine. I am seeing this
issue only on db410c board.

>>
>> One more thing is for pstore dmesg-ramoops, I had to change
>> late_initcall to postcore_initcall which brings the question as to why
>> we changed to late_initcall?
>> Simple git blame shows to support crypto compress api, but is it really
>> helpful? A lot of boottime issues can be caught with pstore enabled at
>> postcore_initcall rather than late_initcall, this backtrace
>> is just one example. Is there any way we could change this?
>
> Does it break if the crypto is not initialized? Perhaps add a command
> line flag to have it happen earlier:
>

I didnt see any breakage, have been using ramoops with postcore_initcall
for sometime now.

> ramoops=earlyinit
>
> and add a postcore_initcall that checks if that flag is set, and if so,
> it does the work then, and the late_initcall() will do nothing.
>
> That way, you can still have unmodified kernels use pstore when it
> crashes at boot up.
>

Sounds good.

Thanks,
Sai

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