On Mon, Aug 19, 2013 at 10:16:52AM -0700, Josh Triplett wrote: > On Mon, Aug 19, 2013 at 09:09:45AM -0700, Paul E. McKenney wrote: > > On Sun, Aug 18, 2013 at 09:19:25PM -0700, Josh Triplett wrote: > > > On Sun, Aug 18, 2013 at 08:55:28PM -0700, Paul E. McKenney wrote: > > > > On Sat, Aug 17, 2013 at 07:54:20PM -0700, Josh Triplett wrote: > > > > > On Sat, Aug 17, 2013 at 07:25:13PM -0700, Paul E. McKenney wrote: > > > > > > From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > > > > > > > > > > > > This commit adds a object_debug option to rcutorture to allow the > > > > > > debug-object-based checks for duplicate call_rcu() invocations to > > > > > > be deterministically tested. > > > > > > > > > > > > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > > > > > Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > > > > > > Cc: Sedat Dilek <sedat.di...@gmail.com> > > > > > > Cc: Davidlohr Bueso <davidlohr.bu...@hp.com> > > > > > > Cc: Rik van Riel <r...@surriel.com> > > > > > > Cc: Thomas Gleixner <t...@linutronix.de> > > > > > > Cc: Linus Torvalds <torva...@linux-foundation.org> > > > > > > Tested-by: Sedat Dilek <sedat.di...@gmail.com> > > > > > > > > > > Two comments below; with those fixed, > > > > > Reviewed-by: Josh Triplett <j...@joshtriplett.org> > > > > > > > > > > > --- > > > > > > @@ -100,6 +101,8 @@ module_param(fqs_stutter, int, 0444); > > > > > > MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)"); > > > > > > module_param(n_barrier_cbs, int, 0444); > > > > > > MODULE_PARM_DESC(n_barrier_cbs, "# of callbacks/kthreads for > > > > > > barrier testing"); > > > > > > +module_param(object_debug, int, 0444); > > > > > > +MODULE_PARM_DESC(object_debug, "Enable debug-object double > > > > > > call_rcu() testing"); > > > > > > > > > > modules-next has a change to ignore and warn about > > > > > unknown module parameters. Thus, I'd suggest wrapping the ifdef > > > > > around > > > > > this module parameter, so it doesn't exist at all without > > > > > CONFIG_DEBUG_OBJECTS_RCU_HEAD. > > > > > > > > > > Alternatively, consider providing the test unconditionally, and just > > > > > printing a big warning message saying that it's going to cause > > > > > corruption in the !CONFIG_DEBUG_OBJECTS_RCU_HEAD case. > > > > > > > > I currently do something like the above. The module parameter > > > > is defined unconditionally, but the actual tests are under #ifdef > > > > CONFIG_DEBUG_OBJECTS_RCU_HEAD. If you specify object_debug for a > > > > !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel, the pr_alert() below happens, > > > > and the test is omitted, thus avoiding the list corruption. > > > > > > > > Seem reasonable? > > > > > > That's exactly the bit I was commenting on. I'm saying that you should > > > either make the test unconditional (perhaps with a warning saying it's > > > about to cause list corruption), or you should compile out the module > > > parameter as well and then you don't need the pr_alert (since current > > > kernels will emit a warning when you pass a non-existent module > > > parameter). > > > > > > Personally, I'd go with the latter. > > > > Ah, the problem is the ugly ifdef in the middle of a function. Yeah, > > that is a problem in need of fixing. No idea what I was thinking... > > > > How about if I pull that block of code out into its own function, and > > #ifdef the function body. For example, something like that shown below. > [...] > > static void rcu_test_debug_objects(void) > > { > > #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD > > struct rcu_head rh1; > > struct rcu_head rh2; > > > > init_rcu_head_on_stack(&rh1); > > init_rcu_head_on_stack(&rh2); > > pr_alert("rcutorture: WARN: Duplicate call_rcu() test starting.\n"); > > local_irq_disable(); /* Make it hard to finish grace period. */ > > call_rcu(&rh1, rcu_torture_leak_cb); /* start grace period. */ > > call_rcu(&rh2, rcu_torture_err_cb); > > call_rcu(&rh2, rcu_torture_err_cb); /* duplicate callback. */ > > local_irq_enable(); > > rcu_barrier(); > > pr_alert("rcutorture: WARN: Duplicate call_rcu() test complete.\n"); > > destroy_rcu_head_on_stack(&rh1); > > destroy_rcu_head_on_stack(&rh2); > > #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ > > pr_alert("rcutorture: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing > > duplicate call_rcu()\n"); > > #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ > > } > > That's a major improvement, but I'd still suggest a couple more changes: > move the if for the config option into that function inside the ifdef, > wrap the config parameter itself in an ifdef so it doesn't exist without > CONFIG_DEBUG_OBJECTS_RCU_HEAD, and drop the #else branch since the > kernel will already emit a warning if you use the module parameter with > !CONFIG_DEBUG_OBJECTS_RCU_HEAD.
I really feel the need to distinguish between "that is never a valid parameter to rcutorture" (given by the module-parameter parser) and "that parameter is valid, but cannot be used in this case, and here are the consequences", so I will keep the pr_alert(). But definitely fix the mid-function #ifdef! 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/