Re: BUG: sleeping function called from invalid context - seen with UML

[Richard Weinberger]

John,

Am 02.08.2016 um 18:17 schrieb John Stultz:
> I'm trying to run UML with recent upstream kernels, and I've been
> seeing the following BUG trigger over and over:

Geez, I forgot to pickup my own patch. ;-\
Can you try https://www.mail-archive.com/user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx/msg09775.html?

Thanks,
//richard

> BUG: sleeping function called from invalid context at mm/slab.h:393
> in_atomic(): 0, irqs_disabled(): 1, pid: 0, name: swapper
> CPU: 0 PID: 0 Comm: swapper Tainted: G        W       4.7.0-09120-ge48af7a #794
> Stack:
>  603e1d20 60069689 600976ea 6002fb08
>  00000000 00000000 603e1d30 601c6336
>  603e1d80 60058225 603e1d60 603e4e50
> Call Trace:
>  [<600976ea>] ? printk+0x0/0x94
>  [<6001d345>] show_stack+0xfe/0x158
>  [<60069689>] ? dump_stack_print_info+0xe1/0xea
>  [<600976ea>] ? printk+0x0/0x94
>  [<6002fb08>] ? get_signals+0x0/0xf
>  [<601c6336>] dump_stack+0x2a/0x2c
>  [<60058225>] ___might_sleep+0x181/0x18c
>  [<60058307>] __might_sleep+0xd7/0xe2
>  [<60069fa1>] ? handle_irq_event+0x56/0x6a
>  [<600cf35f>] __kmalloc+0x5a/0x121
>  [<6001bc10>] uml_kmalloc+0x13/0x15
>  [<6002e19d>] __wrap_malloc+0x3f/0x71
>  [<6002fa46>] sig_handler_common+0x3e/0x100
>  [<6002fa08>] ? sig_handler_common+0x0/0x100
>  [<6002f944>] ? block_signals+0x0/0x16
>  [<600976ea>] ? printk+0x0/0x94
>  [<6002f9c5>] unblock_signals+0x6b/0xae
>  [<601cc073>] ? strlen+0x0/0x16
>  [<6001c35b>] arch_cpu_idle+0x53/0x5a
>  [<601cc073>] ? strlen+0x0/0x16
>  [<6006029d>] default_idle_call+0x32/0x34
>  [<6007db99>] ? tick_nohz_idle_enter+0x75/0x77
>  [<60060353>] cpu_startup_entry+0xb4/0x11d
>  [<6006009e>] ? complete+0x0/0x5a
>  [<600382ec>] ? kernel_thread+0x0/0x2d
>  [<600382ec>] ? kernel_thread+0x0/0x2d
>  [<602fe646>] rest_init+0xa7/0xae
>  [<6002fb08>] ? get_signals+0x0/0xf
>  [<6002fb08>] ? get_signals+0x0/0xf
>  [<60001bc0>] start_kernel+0x529/0x538
>  [<60003626>] start_kernel_proc+0x49/0x4d
>  [<600660b8>] ? kmsg_dump_register+0x84/0x93
>  [<6001bf03>] new_thread_handler+0x81/0xa3
>  [<600035db>] ? kmsg_dumper_stdout_init+0x1a/0x1c
>  [<6001ee17>] uml_finishsetup+0x54/0x59
> 
> 
> 
> I tried to bisect it down, and it apparently popped up in the v4.7
> merge window, with the following commit:
> 
> b6024b21fec8 ("um: extend fpstate to _xstate to support YMM
> registers") which adds a malloc call to the sig_handler
> 
> 
> Unfortunately just reverting that patch against v4.7 doesn't work, as
> I then hit:
> 
> This architecture does not have kernel memory protection.
> Registers -
>         0       0x2
>         1       0x0
>         2       0x0
>         3       0x0
>         4       0x0
>         5       0x0
>         6       0x0
>         7       0x0
>         8       0x0
>         9       0x0
>         10      0x0
>         11      0x0
>         12      0x0
>         13      0x0
>         14      0x0
>         15      0x0
>         16      0x10007b
>         17      0x0
>         18      0x0
>         19      0x0
>         20      0x0
>         21      0x0
>         22      0x0
>         23      0x0
>         24      0x0
>         25      0x0
>         26      0x0
> Kernel panic - not syncing: do_syscall_stub : PTRACE_SETREGS failed, errno = 5
> 
> CPU: 0 PID: 1 Comm: swapper Not tainted 4.7.0-00001-g0a9f717 #795
> Stack:
>  80455be0 60068d01 601ce033 60373c73
>  807928f0 60096cdf 80455bf0 601c4109
>  80455d10 600960cd 00002458 807928f0
> Call Trace:
>  [<60096cdf>] ? printk+0x0/0x94
>  [<6001d345>] show_stack+0xfe/0x158
>  [<60068d01>] ? dump_stack_print_info+0xe1/0xea
>  [<601ce033>] ? bust_spinlocks+0x0/0x4f
>  [<60096cdf>] ? printk+0x0/0x94
>  [<601c4109>] dump_stack+0x2a/0x2c
>  [<600960cd>] panic+0x163/0x2f0
>  [<60095f6a>] ? panic+0x0/0x2f0
>  [<60096cdf>] ? printk+0x0/0x94
>  [<60096cdf>] ? printk+0x0/0x94
>  [<60057bb9>] ? __might_sleep+0xd7/0xe2
>  [<6003191a>] run_syscall_stub+0x145/0x2d4
>  [<60096cdf>] ? printk+0x0/0x94
>  [<600cda05>] ? kmem_cache_alloc+0x0/0xff
>  [<6003302e>] write_ldt_entry+0x84/0x8f
>  [<60033298>] init_new_ldt+0x25f/0x350
>  [<600cda05>] ? kmem_cache_alloc+0x0/0xff
>  [<6001f165>] init_new_context+0x102/0x14e
>  [<6009fa4a>] ? __get_free_pages+0x1c/0x5a
>  [<60063cc9>] ? __raw_spin_lock_init+0x0/0x1e
>  [<600359bf>] mm_init+0x1cc/0x211
>  [<600cdad3>] ? kmem_cache_alloc+0xce/0xff
>  [<60035e73>] mm_alloc+0x62/0x6d
>  [<600da275>] do_execveat_common+0x2b3/0x65e
>  [<600da641>] do_execve+0x21/0x23
>  [<6001a6d8>] run_init_process+0x3b/0x3f
>  [<6001a69d>] ? run_init_process+0x0/0x3f
>  [<60096cdf>] ? printk+0x0/0x94
>  [<602f9b5c>] kernel_init+0xbf/0x156
>  [<6001bf03>] new_thread_handler+0x81/0xa3
> 
> 
> Any thoughts on how to get around this?
> 
> thanks
> -john
>