On Thu, Feb 12, 2015 at 02:26:42PM +0100, Jiri Slaby wrote: > On 02/12/2015, 04:21 AM, Josh Poimboeuf wrote: > > Ingo, Peter, > > > > Would you have any objections to making task_rq_lock/unlock() non-static > > (or moving them to kernel/sched/sched.h) so they can be called by the > > livepatch code? > > > > To provide some background, I'm looking for a way to temporarily prevent > > a sleeping task from running while its stack is examined, to decide > > whether it can be safely switched to the new patching "universe". For > > more details see klp_transition_task() in the patch below. > > > > Using task_rq_lock() is the most straightforward way I could find to > > achieve that. > > Hi, I cannot speak whether it is the proper way or not. > > But if so, would it make sense to do the opposite: expose an API to walk > through the processes' stack and make the decision? Concretely, move > parts of klp_stacktrace_address_verify_func to sched.c or somewhere in > kernel/sched/ and leave task_rq_lock untouched. Yeah, it makes sense in theory. But I'm not sure how to do that in a way that prevents races when switching the task's universe. I think we need the rq locked for both the stack walk and the universe switch. In general, I agree it would be good to find a way to keep the rq locking functions in sched.c. -- Josh -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
