On Wed, May 07, 2014 at 04:43:13PM -0700, Paul E. McKenney wrote: > On Wed, May 07, 2014 at 02:16:49PM -0700, j...@joshtriplett.org wrote: > > On Mon, Apr 28, 2014 at 05:24:49PM -0700, Paul E. McKenney wrote: > > > From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > > > > > > The rcutorture output currently does not distinguish between stalls in > > > the RCU implementation and stalls in the rcu_torture_writer() kthreads. > > > This commit therefore adds some diagnostics to help distinguish between > > > these two conditions, at least for the non-SRCU implementations. (SRCU > > > does not provide evidence of update-side forward progress by design.) > > > > > > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > > > The concept makes sense, and the writer state annotations seem like a > > useful debugging mechanism, but having RCU know about RCU torture types > > seems fundamentally wrong. This mechanism accesses rcu_state, which is > > already implementation-specific, so why not just only define the > > function for the RCU implementations that support it, and then have a > > function pointer in the torture-test structure to report a stall? > > Ouch. It is worse than that! When running RCU-bh or RCU-sched, > the current code incorrectly returns the statistics for RCU. > So I do need some way for rcutorture to tell RCU which flavor > it is testing. > > One thing I could do would be to pass in a pointer to the call_rcu() > function (cur_ops->call from rcutorture's viewpoint), then scan the > rcu_state structures looking for the selected flavor (rsp->call from > tree.c's viewpoint). In the SRCU and RCU-busted cases, the flavor would > not be found, and I could then just set everything to zero. > > Does that seem reasonable, or is there a better way to do this?
That search seems rather too hackish; why not just declare one stats-returning function per RCU flavor, and put the pointer to the corresponding function in the structure for each test type? - Josh Triplett -- 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/
