Messages in this thread | | | Subject | Re: [PATCH RFC tip/core/rcu 05/11] rcu: add comment saying why DEBUG_OBJECTS_RCU_HEAD depends on PREEMPT. | From | Steven Rostedt <> | Date | Tue, 22 Feb 2011 22:23:29 -0500 |
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On Tue, 2011-02-22 at 17:39 -0800, Paul E. McKenney wrote: > The build will break if you change the Kconfig to allow > DEBUG_OBJECTS_RCU_HEAD and !PREEMPT, so document the reasoning > near where the breakage would occur. > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > kernel/rcupdate.c | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c > index afd21d1..f3240e9 100644 > --- a/kernel/rcupdate.c > +++ b/kernel/rcupdate.c > @@ -214,6 +214,11 @@ static int rcuhead_fixup_free(void *addr, enum debug_obj_state state) > * Ensure that queued callbacks are all executed. > * If we detect that we are nested in a RCU read-side critical > * section, we should simply fail, otherwise we would deadlock. > + * Note that the machinery to reliably determine whether > + * or not we are in an RCU read-side critical section > + * exists only in the preemptible RCU implementations > + * (TINY_PREEMPT_RCU and TREE_PREEMPT_RCU), which is why > + * DEBUG_OBJECTS_RCU_HEAD is disallowed if !PREEMPT. > */
Shouldn't this comment also be in the kconfig where DEBUG_OBJECTS_RCU_HEAD is defined?
-- Steve
> if (rcu_preempt_depth() != 0 || preempt_count() != 0 || > irqs_disabled()) {
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