On Sat, 2013-08-31 at 12:55 -0700, Paul E. McKenney wrote: > On Sat, Aug 31, 2013 at 01:11:29AM -0400, Steven Rostedt wrote: > > From: "Steven Rostedt (Red Hat)" <rost...@goodmis.org> > > > > Having the RCU unsafe checker running when function graph is enabled > > can cause a live lock. That's because the RCU unsafe checker enables > > full lockdep debugging on RCU which does a lot of interal calls that > > may be traced by the function graph tacer. This adds quite a bit of > > s/tacer/tracer/ (Yeah, yeah, picky, picky!) > > > overhead and can possibly live lock the system. > > > > Just do not do the RCU unsafe checks when function graph tracer is > > enabled. > > > > Signed-off-by: Steven Rostedt <rost...@goodmis.org> > > One question: How does the user/tester/developer know that RCU-unsafe > checks have been disabled by function-graph tracing? Would it make > sense to print something to dmesg calling this out? Or do the transitions > happen too often?
Ideally, (for 3.13) I plan on having this be a sysctl switch. That will be 1 or 0, depending on if it is enabled or not. But yeah, I can add a printk to show that the kernel changed it. It doesn't happen often, and mainly by a user (or selftest). -- Steve > > Thanx, Paul > > > --- -- 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/
