On Wed, 2013-07-10 at 14:36 -0700, H. Peter Anvin wrote: > On 07/10/2013 02:31 PM, Jiri Kosina wrote: > > > > If any CPU instruction execution would collide with the patching, > > it'd be trapped by the int3 breakpoint and redirected to the provided > > "handler" (which would typically mean just skipping over the patched > > region, acting as "nop" has been there, in case we are doing nop -> jump > > and jump -> nop transitions). > > > > I'm wondering if it would be easier/more general to just return to the > instruction. The "more general" bit would allow this to be used for > other things, like alternatives, and perhaps eventually dynamic call > patching. > > Returning to the instruction will, in effect, be a busy-wait for the > faulted CPU until the patch is complete; more or less what stop_machine > would do, but only for a CPU which actually strays into the affected region. >
Wont work for ftrace, as it patches all functions, it even patches functions used to do the changes. Thus, it would cause a deadlock if a breakpoint were to spin till the changes were finished. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
