• Jeff Dike's avatar
    [PATCH] uml: breakpoint an arbitrary thread · 3eddddcf
    Jeff Dike authored
    
    
    This patch implements a stack trace for a thread, not unlike sysrq-t does.
    The advantage to this is that a break point can be placed on showreqs, so that
    upon showing the stack, you jump immediately into the debugger.  While sysrq-t
    does the same thing, sysrq-t shows *all* threads stacks.  It also doesn't work
    right now.  In the future, I thought it might be acceptable to make this show
    all pids stacks, but perhaps leaving well enough alone and just using sysrq-t
    would be okay.  For now, upon receiving the stack command, UML switches
    context to that thread, dumps its registers, and then switches context back to
    the original thread.  Since UML compacts all threads into one of 4 host
    threads, this sort of mechanism could be expanded in the future to include
    other debugging helpers that sysrq does not cover.
    
    Note by jdike - The main benefit to this is that it brings an arbitrary thread
    back into context, where it can be examined by gdb.  The fact that it dumps it
    stack is secondary.  This provides the capability to examine a sleeping
    thread, which has existed in tt mode, but not in skas mode until now.
    
    Also, the other threads, that sysrq doesn't cover, can be gdb-ed directly
    anyway.
    
    Signed-off-by: default avatarAllan <Graves&lt;allan.graves@gmail.com>
    Signed-off-by: default avatarJeff Dike <jdike@addtoit.com>
    Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    3eddddcf