On Thu, 2014-03-13 at 18:37 +0000, Will Deacon wrote: > > > No, return_hooker is consistent with all the other archs. Hey, it's a > > rugby position! Note, which I was when I played. ;-) > > Hehe, in which case your children will be able to execute that line of > ftrace! >
My kids already know I was :-) > > > > > > > + trace.func = self_addr; > > > > > > in kernel/ftrace/ftrace.c there's an smb_wmb() between setting up > > > tracing_graph_pause and setting the ret_stack with a comment saying: > > > > > > /* Make sure the tasks see the -1 first: */ > > > > > > Why don't we have a corresponding read-barrier here? > > > > The corresponding rmb is in kernel/trace/trace_function_graph > > ftrace_push_return_trace(). > > Okey doke then, I guess we don't really care about tracing_graph_pause > getting out-of-sync with curr_ret_stack. Yep, the tracing_graph_pause is more to prevent crazy stuff happening when an interrupt comes in. So it is just local cpu context, and doesn't have issues with other CPUS. If it takes a bit for the task to see it go to zero, the worse thing is that you might miss a few tracing functions until that gets synced. Which will probably happen by the time tracing is fully activated anyway. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
