[Crash-utility] Unable to switch stack frames while using crash

[Dave Anderson]

----- Original Message -----
> On 24 June 2011 14:40, Dave Anderson < anderson at redhat.com > wrote:
> 
> 
> And for that matter, since tty->read_cnt is 0 above,
> your original question as to how that code path was taken to
> begin with is also valid.
> 
> Surely that implies tty->read_cnt has been modified since it was
> tested, and hence you're looking at concurrency issues?

Yeah, although the contents tty->read_buf are hard to explain. 
It gets allocated during n_tty_open() and freed during n_tty_close().
And at the beginning of n_tty_read() there's:

        BUG_ON(!tty->read_buf);

and the dump-time contents show a buffer allocated:

crash> tty_struct ffff8802cbd54800
 struct tty_struct { ...
   magic = 21505,
   driver = 0xffff88031b54ea00,
   ops = 0xffffffff8130f650,
   name = "pts9\000\...",
   driver_data = 0xffff88029c8a9668,
   icanon = 1 '\001',
   read_buf = 0xffff8802cbfe6000 "",
   read_head = 0,
   read_tail = 0,
   read_cnt = 0,
   ...

but it's a NULL pointer when read during the function?  

Dave