Messages in this thread | | | Subject | Re: [PATCH] debug rcu head support !PREEMPT config | From | Steven Rostedt <> | Date | Wed, 23 Feb 2011 10:27:07 -0500 |
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On Wed, 2011-02-23 at 10:13 -0500, Mathieu Desnoyers wrote: > Remove DEBUG_RCU_HEAD dependency on PREEMPT config. Handle the unability to > detect if within a RCU read-side critical section by never performing any > attempt to recover from a failure situation in the fixup handlers. Just print > the warnings. > > This patch is only compile-tested. > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > --- > kernel/rcupdate.c | 17 +++++++++++++++++ > lib/Kconfig.debug | 2 +- > 2 files changed, 18 insertions(+), 1 deletion(-) > > Index: linux-2.6-lttng/lib/Kconfig.debug > =================================================================== > --- linux-2.6-lttng.orig/lib/Kconfig.debug > +++ linux-2.6-lttng/lib/Kconfig.debug > @@ -313,7 +313,7 @@ config DEBUG_OBJECTS_WORK > > config DEBUG_OBJECTS_RCU_HEAD > bool "Debug RCU callbacks objects" > - depends on DEBUG_OBJECTS && PREEMPT > + depends on DEBUG_OBJECTS > help > Enable this to turn on debugging of RCU list heads (call_rcu() usage). > > Index: linux-2.6-lttng/kernel/rcupdate.c > =================================================================== > --- linux-2.6-lttng.orig/kernel/rcupdate.c > +++ linux-2.6-lttng/kernel/rcupdate.c > @@ -142,7 +142,14 @@ static int rcuhead_fixup_init(void *addr > * 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. > + * In !PREEMPT configurations, there is no way to tell if we are > + * in a RCU read-side critical section or not, so we never > + * attempt any fixup and just print a warning. > */ > +#ifndef CONFIG_PREEMPT > + WARN_ON(1); > + return 0; > +#endif > if (rcu_preempt_depth() != 0 || preempt_count() != 0 || > irqs_disabled()) { > WARN_ON(1); > @@ -184,7 +191,14 @@ static int rcuhead_fixup_activate(void * > * 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. > + * In !PREEMPT configurations, there is no way to tell if we are > + * in a RCU read-side critical section or not, so we never > + * attempt any fixup and just print a warning. > */ > +#ifndef CONFIG_PREEMPT > + WARN_ON(1); > + return 0; > +#endif > if (rcu_preempt_depth() != 0 || preempt_count() != 0 || > irqs_disabled()) { > WARN_ON(1); > @@ -214,6 +228,9 @@ static int rcuhead_fixup_free(void *addr > * 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. > + * In !PREEMPT configurations, there is no way to tell if we are > + * in a RCU read-side critical section or not, so we never > + * attempt any fixup and just print a warning. > */ > #ifndef CONFIG_PREEMPT > WARN_ON(1);
Hmm, I wonder if s/WARN_ON/WARN_ON_ONCE/g is in order. Why spam the console if it happens to trigger all the time?
-- Steve
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