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Date:      Wed, 16 Oct 2013 02:18:27 +0800
From:      Jia-Shiun Li <jiashiun@gmail.com>
To:        "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>
Subject:   BBB triggered trap when disconnecting uart
Message-ID:  <CAHNYxxPe7maWJMNqXRV4YcpxSdHBv6pKDdMzyVLL8d3Kus7mbg@mail.gmail.com>

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I originally thought it hanged when I unplug my USB-serial dongle (a
PL2303-based one on Windows). But looking closely I found it was
actually dropping to ddb, because if pressed Enter in terminal window
it will continue. And I got the following back trace. Is it possible
the USB-serial chip or term (putty) sent garbage chars to trigger it,
or simply because something went wrong in uart_intr?

The behavior is reproducible. Also happens when I suspend/resume PC.
And system is

FreeBSD beaglebone 10.0-ALPHA4 FreeBSD 10.0-ALPHA4 #0 r256041: Fri Oct
 4 16:13:26 CST 2013
jsli@4cbsd:/root/crochet-freebsd/work/obj/arm.armv6/usr/src/sys/BEAGLEBONE
 arm


---- 9< --------- 9< --------- 9< -----
t
Tracing pid 65332 tid 100108 td 0xc4d9f960
db_trace_self() at db_trace_self
         pc = 0xc052f8fc  lr = 0xc022c128 (db_stack_trace+0xf4)
         sp = 0xde9467a0  fp = 0xde9467b8
        r10 = 0xc0626900
db_stack_trace() at db_stack_trace+0xf4
         pc = 0xc022c128  lr = 0xc022ba94 (db_command+0x264)
         sp = 0xde9467c0  fp = 0xde946860
         r4 = 0x00000000  r5 = 0x00000000
         r6 = 0xc059b343
db_command() at db_command+0x264
         pc = 0xc022ba94  lr = 0xc022b804 (db_command_loop+0x60)
         sp = 0xde946868  fp = 0xde946878
         r4 = 0xc0571596  r5 = 0xc058b91b
         r6 = 0xc07ccbb0  r7 = 0xde946a48
         r8 = 0xc4d9f960  r9 = 0xc0669a04
        r10 = 0xc0626b70
db_command_loop() at db_command_loop+0x60
         pc = 0xc022b804  lr = 0xc022e204 (db_trap+0xdc)
         sp = 0xde946880  fp = 0xde9469a0
         r4 = 0x00000000  r5 = 0xde946888
         r6 = 0xc0669a30
db_trap() at db_trap+0xdc
         pc = 0xc022e204  lr = 0xc038f5bc (kdb_trap+0xd4)
         sp = 0xde9469a8  fp = 0xde9469c8
         r4 = 0x00000000  r5 = 0x00000001
         r6 = 0xc0669a30  r7 = 0xde946a48
kdb_trap() at kdb_trap+0xd4
         pc = 0xc038f5bc  lr = 0xc0541e70 (undefinedinstruction+0x2b0)
         sp = 0xde9469d0  fp = 0xde946a40
         r4 = 0x00000000  r5 = 0xc0541b1c
         r6 = 0x00000000  r7 = 0xe7ffffff
         r8 = 0xc4d9f960  r9 = 0xde946a48
        r10 = 0xc038ee34
undefinedinstruction() at undefinedinstruction+0x2b0
         pc = 0xc0541e70  lr = 0xc0531134 (exception_exit)
         sp = 0xde946a48  fp = 0xde946aa0
         r4 = 0x00000001  r5 = 0xc27d4a00
         r6 = 0x00060000  r7 = 0xc062ba1c
         r8 = 0xc27d4b74  r9 = 0x0000ff7f
        r10 = 0x00000000
exception_exit() at exception_exit
         pc = 0xc0531134  lr = 0xc038ee24 (kdb_break+0x50)
         sp = 0xde946a9c  fp = 0xde946aa0
         r0 = 0xc0669a14  r1 = 0xc057168a
         r2 = 0x00000000  r3 = 0x60000193
         r4 = 0x00000001  r5 = 0xc27d4a00
         r6 = 0x00060000  r7 = 0xc062ba1c
         r8 = 0xc27d4b74  r9 = 0x0000ff7f
        r10 = 0x00000000 r12 = 0x00000000
$a() at $a
         pc = 0xc038ee38  lr = 0xc025df78 (uart_intr+0xa4)
         sp = 0xde946aa8  fp = 0xde946ae8
         r4 = 0xc264ed00
uart_intr() at uart_intr+0xa4
         pc = 0xc025df78  lr = 0xc032b594 (intr_event_handle+0x84)
         sp = 0xde946af0  fp = 0xde946b18
         r4 = 0xc264ed00  r5 = 0xde946b38
         r6 = 0xc4d9f960  r7 = 0xc0585a55
         r8 = 0xc0585a2e  r9 = 0x00000000
        r10 = 0xc27c2bc0
intr_event_handle() at intr_event_handle+0x84
         pc = 0xc032b594  lr = 0xc0532350 (arm_handler_execute+0x50)
         sp = 0xde946b20  fp = 0xde946b30
         r4 = 0xde946b38  r5 = 0x00000048
         r6 = 0xc0652420  r7 = 0xc07ca0d8
         r8 = 0x20a87000  r9 = 0x00000000
        r10 = 0x00000953
arm_handler_execute() at arm_handler_execute+0x50
         pc = 0xc0532350  lr = 0xc054fcc8 (irq_entry+0x6c)
         sp = 0xde946b38  fp = 0xde946bc8
         r4 = 0xc09b7a30  r5 = 0xc05afd2b
         r6 = 0xc05afd2b  r7 = 0xc09b7a30
irq_entry() at irq_entry+0x6c
         pc = 0xc054fcc8  lr = 0xc0360970 (_sx_sunlock+0x74)
         sp = 0xde946b8c  fp = 0xde946bc8
         r0 = 0x00000000  r1 = 0x00000000
         r2 = 0xc05afd2b  r3 = 0x00000fe2
         r4 = 0xc09b7a30  r5 = 0xc05afd2b
         r6 = 0xc05afd2b  r7 = 0xc09b7a30
         r8 = 0x20a87000  r9 = 0x00000000
        r10 = 0x00000953 r12 = 0x000000c0
witness_unlock() at witness_unlock+0x48
         pc = 0xc03a9bf0  lr = 0xc0360970 (_sx_sunlock+0x74)
         sp = 0xde946bd0  fp = 0xde946bf0
         r4 = 0xc09b7a30  r5 = 0x00000fe2
         r6 = 0xc05afd2b  r7 = 0xc09b7a40
         r8 = 0x20a87000  r9 = 0x00000000
        r10 = 0x00000953
_sx_sunlock() at _sx_sunlock+0x74
         pc = 0xc0360970  lr = 0xc05108c0 (vm_map_lookup_done+0x44)
         sp = 0xde946bf8  fp = 0xde946bf8
         r4 = 0xde946d10  r5 = 0x00000000
         r6 = 0xc3fa1280  r7 = 0x20a88000
vm_map_lookup_done() at vm_map_lookup_done+0x44
         pc = 0xc05108c0  lr = 0xc05062cc (unlock_and_deallocate+0xc8)
         sp = 0xde946c00  fp = 0xde946c10
unlock_and_deallocate() at unlock_and_deallocate+0xc8
         pc = 0xc05062cc  lr = 0xc0506180 ($a+0xfc)
         sp = 0xde946c18  fp = 0xde946d88
         r4 = 0xc05af61a  r5 = 0x00000000
         r6 = 0xc3fa1280  r7 = 0x20a88000
$a() at $a+0xfc
         pc = 0xc0506180  lr = 0xc0504580 (vm_fault+0x88)
         sp = 0xde946d90  fp = 0xde946db0
         r4 = 0xc09b79e0  r5 = 0x00000002
         r6 = 0xc4d9f960  r7 = 0x20a87000
         r8 = 0x00000000  r9 = 0x00000002
        r10 = 0xc07d0b88
vm_fault() at vm_fault+0x88
         pc = 0xc0504580  lr = 0xc054089c (data_abort_handler+0x2a8)
         sp = 0xde946db8  fp = 0xde946e58
         r4 = 0xc4d9b000  r5 = 0xc4d9f960
         r6 = 0xc05b5d32  r7 = 0xc4d9b0ac
         r8 = 0xde946e60  r9 = 0xde946eb0
        r10 = 0xc09b79e0
data_abort_handler() at data_abort_handler+0x2a8
         pc = 0xc054089c  lr = 0xc0531134 (exception_exit)
         sp = 0xde946e60  fp = 0xbfffdeb0
         r4 = 0x20a87000  r5 = 0x00001000
         r6 = 0x204000c0  r7 = 0x00000138
         r8 = 0x00000000  r9 = 0x204000c8
        r10 = 0x20848080
exception_exit() at exception_exit
         pc = 0xc0531134  lr = 0x000c5fc8 (0xc5fc8)
         sp = 0xde946eb4  fp = 0xbfffdeb0
         r0 = 0x20a87000  r1 = 0x00000f80
         r2 = 0xa5a5a5a5  r3 = 0xa5a5a5a5
         r4 = 0x20a87000  r5 = 0x00001000
         r6 = 0x204000c0  r7 = 0x00000138
         r8 = 0x00000000  r9 = 0x204000c8
        r10 = 0x20848080 r12 = 0x20a87000
Unable to unwind into user mode
db>

Jia-Shiun.



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