On 07/11/2013 10:35 AM, Steven Rostedt wrote: > 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 > >
I'm not sure this works for jump labels either. Some tracepoints (which use jump_labels) have interrupts disabled across them. Thus, they will spin with interrupts disabled, while we are trying to issue an IPI. Thanks, -Jason -- 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/
