* [PATCH 3/5] rcu/tree: Add support for debug_objects debugging for kfree_rcu() @ 2019-08-27 19:01 Joel Fernandes (Google) 2019-08-28 21:31 ` Paul E. McKenney 0 siblings, 1 reply; 4+ messages in thread From: Joel Fernandes (Google) @ 2019-08-27 19:01 UTC (permalink / raw) To: linux-kernel Cc: Joel Fernandes (Google), byungchul.park, Josh Triplett, Lai Jiangshan, linux-doc, Mathieu Desnoyers, Paul E. McKenney, rcu, Steven Rostedt, kernel-team Make use of RCU's debug_objects debugging support (CONFIG_DEBUG_OBJECTS_RCU_HEAD) similar to call_rcu() and other flavors. We queue the object during the kfree_rcu() call and dequeue it during reclaim. Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects double kfree_rcu() calls. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> --- kernel/rcu/tree.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 9b9ae4db1c2d..64568f12641d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2757,6 +2757,7 @@ static void kfree_rcu_work(struct work_struct *work) for (; head; head = next) { next = head->next; /* Could be possible to optimize with kfree_bulk in future */ + debug_rcu_head_unqueue(head); __rcu_reclaim(rcu_state.name, head); cond_resched_tasks_rcu_qs(); } @@ -2868,6 +2869,13 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) return kfree_call_rcu_nobatch(head, func); + if (debug_rcu_head_queue(head)) { + /* Probable double kfree_rcu() */ + WARN_ONCE(1, "kfree_call_rcu(): Double-freed call. rcu_head %p\n", + head); + return; + } + head->func = func; local_irq_save(flags); /* For safely calling this_cpu_ptr(). */ -- 2.23.0.187.g17f5b7556c-goog ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 3/5] rcu/tree: Add support for debug_objects debugging for kfree_rcu() 2019-08-27 19:01 [PATCH 3/5] rcu/tree: Add support for debug_objects debugging for kfree_rcu() Joel Fernandes (Google) @ 2019-08-28 21:31 ` Paul E. McKenney 2019-08-28 21:43 ` Joel Fernandes 0 siblings, 1 reply; 4+ messages in thread From: Paul E. McKenney @ 2019-08-28 21:31 UTC (permalink / raw) To: Joel Fernandes (Google) Cc: linux-kernel, byungchul.park, Josh Triplett, Lai Jiangshan, linux-doc, Mathieu Desnoyers, rcu, Steven Rostedt, kernel-team On Tue, Aug 27, 2019 at 03:01:57PM -0400, Joel Fernandes (Google) wrote: > Make use of RCU's debug_objects debugging support > (CONFIG_DEBUG_OBJECTS_RCU_HEAD) similar to call_rcu() and other flavors. Other flavors? Ah, call_srcu(), rcu_barrier(), and srcu_barrier(), right? > We queue the object during the kfree_rcu() call and dequeue it during > reclaim. > > Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects > double kfree_rcu() calls. > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> The code looks good! Thanx, Paul > --- > kernel/rcu/tree.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 9b9ae4db1c2d..64568f12641d 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2757,6 +2757,7 @@ static void kfree_rcu_work(struct work_struct *work) > for (; head; head = next) { > next = head->next; > /* Could be possible to optimize with kfree_bulk in future */ > + debug_rcu_head_unqueue(head); > __rcu_reclaim(rcu_state.name, head); > cond_resched_tasks_rcu_qs(); > } > @@ -2868,6 +2869,13 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) > return kfree_call_rcu_nobatch(head, func); > > + if (debug_rcu_head_queue(head)) { > + /* Probable double kfree_rcu() */ > + WARN_ONCE(1, "kfree_call_rcu(): Double-freed call. rcu_head %p\n", > + head); > + return; > + } > + > head->func = func; > > local_irq_save(flags); /* For safely calling this_cpu_ptr(). */ > -- > 2.23.0.187.g17f5b7556c-goog > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 3/5] rcu/tree: Add support for debug_objects debugging for kfree_rcu() 2019-08-28 21:31 ` Paul E. McKenney @ 2019-08-28 21:43 ` Joel Fernandes 2019-08-28 21:57 ` Paul E. McKenney 0 siblings, 1 reply; 4+ messages in thread From: Joel Fernandes @ 2019-08-28 21:43 UTC (permalink / raw) To: Paul E. McKenney Cc: linux-kernel, byungchul.park, Josh Triplett, Lai Jiangshan, linux-doc, Mathieu Desnoyers, rcu, Steven Rostedt, kernel-team On Wed, Aug 28, 2019 at 02:31:19PM -0700, Paul E. McKenney wrote: > On Tue, Aug 27, 2019 at 03:01:57PM -0400, Joel Fernandes (Google) wrote: > > Make use of RCU's debug_objects debugging support > > (CONFIG_DEBUG_OBJECTS_RCU_HEAD) similar to call_rcu() and other flavors. > > Other flavors? Ah, call_srcu(), rcu_barrier(), and srcu_barrier(), > right? Yes. > > We queue the object during the kfree_rcu() call and dequeue it during > > reclaim. > > > > Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects > > double kfree_rcu() calls. > > > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > The code looks good! thanks, does that mean you'll ack/apply it? :-P - Joel > > Thanx, Paul > > > --- > > kernel/rcu/tree.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 9b9ae4db1c2d..64568f12641d 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -2757,6 +2757,7 @@ static void kfree_rcu_work(struct work_struct *work) > > for (; head; head = next) { > > next = head->next; > > /* Could be possible to optimize with kfree_bulk in future */ > > + debug_rcu_head_unqueue(head); > > __rcu_reclaim(rcu_state.name, head); > > cond_resched_tasks_rcu_qs(); > > } > > @@ -2868,6 +2869,13 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) > > return kfree_call_rcu_nobatch(head, func); > > > > + if (debug_rcu_head_queue(head)) { > > + /* Probable double kfree_rcu() */ > > + WARN_ONCE(1, "kfree_call_rcu(): Double-freed call. rcu_head %p\n", > > + head); > > + return; > > + } > > + > > head->func = func; > > > > local_irq_save(flags); /* For safely calling this_cpu_ptr(). */ > > -- > > 2.23.0.187.g17f5b7556c-goog > > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 3/5] rcu/tree: Add support for debug_objects debugging for kfree_rcu() 2019-08-28 21:43 ` Joel Fernandes @ 2019-08-28 21:57 ` Paul E. McKenney 0 siblings, 0 replies; 4+ messages in thread From: Paul E. McKenney @ 2019-08-28 21:57 UTC (permalink / raw) To: Joel Fernandes Cc: linux-kernel, byungchul.park, Josh Triplett, Lai Jiangshan, linux-doc, Mathieu Desnoyers, rcu, Steven Rostedt, kernel-team On Wed, Aug 28, 2019 at 05:43:20PM -0400, Joel Fernandes wrote: > On Wed, Aug 28, 2019 at 02:31:19PM -0700, Paul E. McKenney wrote: > > On Tue, Aug 27, 2019 at 03:01:57PM -0400, Joel Fernandes (Google) wrote: > > > Make use of RCU's debug_objects debugging support > > > (CONFIG_DEBUG_OBJECTS_RCU_HEAD) similar to call_rcu() and other flavors. > > > > Other flavors? Ah, call_srcu(), rcu_barrier(), and srcu_barrier(), > > right? > > Yes. > > > > We queue the object during the kfree_rcu() call and dequeue it during > > > reclaim. > > > > > > Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects > > > double kfree_rcu() calls. > > > > > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > > > The code looks good! > > thanks, does that mean you'll ack/apply it? :-P Is it independent of 1/5 and 2/5? Thanx, Paul > - Joel > > > > > Thanx, Paul > > > > > --- > > > kernel/rcu/tree.c | 8 ++++++++ > > > 1 file changed, 8 insertions(+) > > > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > > index 9b9ae4db1c2d..64568f12641d 100644 > > > --- a/kernel/rcu/tree.c > > > +++ b/kernel/rcu/tree.c > > > @@ -2757,6 +2757,7 @@ static void kfree_rcu_work(struct work_struct *work) > > > for (; head; head = next) { > > > next = head->next; > > > /* Could be possible to optimize with kfree_bulk in future */ > > > + debug_rcu_head_unqueue(head); > > > __rcu_reclaim(rcu_state.name, head); > > > cond_resched_tasks_rcu_qs(); > > > } > > > @@ -2868,6 +2869,13 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > > if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) > > > return kfree_call_rcu_nobatch(head, func); > > > > > > + if (debug_rcu_head_queue(head)) { > > > + /* Probable double kfree_rcu() */ > > > + WARN_ONCE(1, "kfree_call_rcu(): Double-freed call. rcu_head %p\n", > > > + head); > > > + return; > > > + } > > > + > > > head->func = func; > > > > > > local_irq_save(flags); /* For safely calling this_cpu_ptr(). */ > > > -- > > > 2.23.0.187.g17f5b7556c-goog > > > ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-08-28 21:58 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-08-27 19:01 [PATCH 3/5] rcu/tree: Add support for debug_objects debugging for kfree_rcu() Joel Fernandes (Google) 2019-08-28 21:31 ` Paul E. McKenney 2019-08-28 21:43 ` Joel Fernandes 2019-08-28 21:57 ` Paul E. McKenney
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