do_undefinstr call sem down_read?

[Alex Shi]

Hi, Russell,

I caught the following issue few times on my panda board on lsk. but I track the code
path, looks like the upstream kernel has the same problem too.

the interrupt handler do_undefinstr --> arm_notify_die --> die --> ...
			exit_signals --> threadgroup_change_begin --> down_read
and then down_read maybe get into sleep.
Is it a issue which needs to be fixed? or I over concern on this?

[   30.618469] BUG: sleeping function called from invalid context at kernel/rwsem.c:20
[   30.618469] in_atomic(): 0, irqs_disabled(): 128, pid: 809, name: jbd2/mmcblk0p2-
[   30.628540] INFO: lockdep is turned off.
[   30.638671] irq event stamp: 1372
[   30.638671] hardirqs last  enabled at (1371): [<c00c1fa1>] get_page_from_freelist+0x279/0x434
[   30.648529] hardirqs last disabled at (1372): [<c050cbb3>] __und_svc+0x33/0x5c
[   30.658905] softirqs last  enabled at (0): [<c002f22a>] copy_process.part.52+0x31a/0xdf4
[   30.658905] softirqs last disabled at (0): [<  (null)>]   (null)
[   30.669433] CPU: 0 PID: 809 Comm: jbd2/mmcblk0p2- Tainted: G      D W    3.10.37+ #109
[   30.682281] [<c001292d>] (unwind_backtrace+0x1/0xcc) from [<c0010279>] (show_stack+0x11/0x14)
[   30.691314] [<c0010279>] (show_stack+0x11/0x14) from [<c050aae7>] (down_read+0x1f/0x44)
[   30.699829] [<c050aae7>] (down_read+0x1f/0x44) from [<c00415c5>] (exit_signals+0x19/0xe4)
[   30.708496] [<c00415c5>] (exit_signals+0x19/0xe4) from [<c0034459>] (do_exit+0x81/0x870)
[   30.717071] [<c0034459>] (do_exit+0x81/0x870) from [<c00105af>] (die+0x333/0x350)
[   30.725036] [<c00105af>] (die+0x333/0x350) from [<c0008417>] (do_undefinstr+0x10b/0x13c)
[   30.733612] [<c0008417>] (do_undefinstr+0x10b/0x13c) from [<c050cbe3>] (__und_svc_finish+0x1/0x3e)
[   30.743103] Exception stack(0xedd5fc50 to 0xedd5fc98)
[   30.748443] fc40:                                     c13c14e0 80000000 00000080 00000000
[   30.757141] fc60: c13c14e0 0000000c eac67284 c13c14e0 edc11518 c0df95c0 c0824410 eac67240
[   30.765808] fc80: 00000000 edd5fcd8 c00171f9 c00cf998 80000133 ffffffff
[   30.772827] [<c050cbe3>] (__und_svc_finish+0x1/0x3e) from [<c00cf998>] (page_mapping+0x20/0x38)
[   30.782073] [<c00cf998>] (page_mapping+0x20/0x38) from [<c00171f9>] (flush_dcache_page+0x1d/0x60)
[   30.791473] [<c00171f9>] (flush_dcache_page+0x1d/0x60) from [<c00e26c3>] (blk_queue_bounce+0x1a3/0x2a0)
[   30.801452] [<c00e26c3>] (blk_queue_bounce+0x1a3/0x2a0) from [<c02ca5bb>] (blk_queue_bio+0x1f/0x364)
[   30.811157] [<c02ca5bb>] (blk_queue_bio+0x1f/0x364) from [<c02c9661>] (generic_make_request+0x65/0x88)
[   30.821014] [<c02c9661>] (generic_make_request+0x65/0x88) from [<c02c96e5>] (submit_bio+0x61/0x104)
[   30.830627] [<c02c96e5>] (submit_bio+0x61/0x104) from [<c010f017>] (_submit_bh+0x127/0x19c)
[   30.839477] [<c010f017>] (_submit_bh+0x127/0x19c) from [<c0194def>] (jbd2_journal_commit_transaction+0x70b/0x161c)
[   30.850463] [<c0194def>] (jbd2_journal_commit_transaction+0-- 


Thanks
    Alex