Re: [uml-devel] Re: Diagnosed and repeatable kernel mode panic in schedule() for 2.6!

[Jeff Dike <jdike@addtoit.com>]

mingo@elte.hu said:
> i cannot reproduce using 2.6.2-rc3-mm1, so it's likely some recent
> breakage. 

I can.  At least the original panic that BlaisorBlade found.  The stack shows
schedule() recursing through switch_to because of a signal arriving at the
wrong time, and the interrupt handler calling schedule():

#6  schedule () at kernel/sched.c:1680
#7  0xa00154f9 in interrupt_end () at arch/um/kernel/process_kern.c:138
#8  0xa001f5aa in userspace (regs=0xa03233b8)
    at arch/um/kernel/skas/process.c:174
#9  0xa001fd9a in fork_handler (sig=10)
    at arch/um/kernel/skas/process_kern.c:103
#10 <signal handler called>
#11 0xa016974d in syscall ()
#12 0x00000001 in ?? ()
#13 0xa7fd388c in ?? ()
#14 0xa7fd395c in ?? ()
#15 0xa0015351 in external_pid (t=0xa0323080)
    at arch/um/kernel/process_kern.c:69
#16 0xa0015487 in set_current (t=0xa0323080)
    at arch/um/kernel/process_kern.c:126
#17 0xa001fb69 in switch_to_skas (prev=0xa0a97740, next=0xa0323080)
    at arch/um/kernel/skas/process_kern.c:40
#18 0xa00154c7 in _switch_to (prev=0xa0a97740, next=0xa0323080, 
    last=0xa0a97740) at arch/um/kernel/process_kern.c:132
#19 0xa0030845 in schedule () at kernel/sched.c:919

So, this seems very wrong.  It's not obvious to me offhand what the correct
fix is, since the scheduler runs with interrupts enabled.  Time to look at what
x86 does, I guess.

				Jeff



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