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" <[email protected]>
> >
> > 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 <[email protected]>
> > Cc: Mathieu Desnoyers <[email protected]>
> > Cc: Sedat Dilek <[email protected]>
> > Cc: Davidlohr Bueso <[email protected]>
> > Cc: Rik van Riel <[email protected]>
> > Cc: Thomas Gleixner <[email protected]>
> > Cc: Linus Torvalds <[email protected]>
> > Tested-by: Sedat Dilek <[email protected]>
>
> Two comments below; with those fixed,
> Reviewed-by: Josh Triplett <[email protected]>
>
> > ---
> > @@ -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?
> > @@ -2163,6 +2178,28 @@ rcu_torture_init(void)
> > firsterr = retval;
> > goto unwind;
> > }
> > + if (object_debug) {
> > +#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: !%s, not testing duplicate call_rcu()\n",
> > + "CONFIG_DEBUG_OBJECTS_RCU_HEAD");
>
> Why put this parameter in a separate string? That makes it harder to
> grep for the full error message. (That's assuming you keep the error
> message, given the comment above.)
Force of habit, fixed. ;-)
Thanx, Paul
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