| Message ID | 20250123185828.460836-4-urezki@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/4] rcutorture: Allow a negative value for nfakewriters | expand |
On Thu, Jan 23, 2025 at 07:58:28PM +0100, Uladzislau Rezki (Sony) wrote: > Switch for using of get_state_synchronize_rcu_full() and > poll_state_synchronize_rcu_full() pair for debug a normal > synchronize_rcu() call. > > Just using "not" full APIs to identify if a grace period > is passed or not might lead to a false kernel splat. > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > --- > include/linux/rcupdate_wait.h | 4 ++++ > kernel/rcu/tree.c | 8 +++----- > 2 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h > index f9bed3d3f78d..a16fc2a9a7d7 100644 > --- a/include/linux/rcupdate_wait.h > +++ b/include/linux/rcupdate_wait.h > @@ -16,6 +16,10 @@ > struct rcu_synchronize { > struct rcu_head head; > struct completion completion; > +#ifdef CONFIG_PROVE_RCU > + /* This is for testing. */ > + struct rcu_gp_oldstate oldstate; > +#endif > }; > void wakeme_after_rcu(struct rcu_head *head); > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 2795d6b5109c..0ae90089ef09 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1612,12 +1612,10 @@ static void rcu_sr_normal_complete(struct llist_node *node) > { > struct rcu_synchronize *rs = container_of( > (struct rcu_head *) node, struct rcu_synchronize, head); > - unsigned long oldstate = (unsigned long) rs->head.func; > > WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && > - !poll_state_synchronize_rcu(oldstate), > - "A full grace period is not passed yet: %lu", > - rcu_seq_diff(get_state_synchronize_rcu(), oldstate)); > + !poll_state_synchronize_rcu_full(&rs->oldstate), > + "A full grace period is not passed yet!\n"); Looks good, but why not also continue printing out the required grace-period sequence number? Yes, there would need to be helper sprintf()-style functions to paper over the difference between Tiny RCU and Tree RCU. ;-) Thanx, Paul > /* Finally. */ > complete(&rs->completion); > @@ -3214,7 +3212,7 @@ static void synchronize_rcu_normal(void) > * snapshot before adding a request. > */ > if (IS_ENABLED(CONFIG_PROVE_RCU)) > - rs.head.func = (void *) get_state_synchronize_rcu(); > + get_state_synchronize_rcu_full(&rs.oldstate); > > rcu_sr_normal_add_req(&rs); > > -- > 2.39.5 >
On Thu, Jan 23, 2025 at 01:52:57PM -0800, Paul E. McKenney wrote: > On Thu, Jan 23, 2025 at 07:58:28PM +0100, Uladzislau Rezki (Sony) wrote: > > Switch for using of get_state_synchronize_rcu_full() and > > poll_state_synchronize_rcu_full() pair for debug a normal > > synchronize_rcu() call. > > > > Just using "not" full APIs to identify if a grace period > > is passed or not might lead to a false kernel splat. > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > > --- > > include/linux/rcupdate_wait.h | 4 ++++ > > kernel/rcu/tree.c | 8 +++----- > > 2 files changed, 7 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h > > index f9bed3d3f78d..a16fc2a9a7d7 100644 > > --- a/include/linux/rcupdate_wait.h > > +++ b/include/linux/rcupdate_wait.h > > @@ -16,6 +16,10 @@ > > struct rcu_synchronize { > > struct rcu_head head; > > struct completion completion; > > +#ifdef CONFIG_PROVE_RCU > > + /* This is for testing. */ > > + struct rcu_gp_oldstate oldstate; > > +#endif > > }; > > void wakeme_after_rcu(struct rcu_head *head); > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 2795d6b5109c..0ae90089ef09 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -1612,12 +1612,10 @@ static void rcu_sr_normal_complete(struct llist_node *node) > > { > > struct rcu_synchronize *rs = container_of( > > (struct rcu_head *) node, struct rcu_synchronize, head); > > - unsigned long oldstate = (unsigned long) rs->head.func; > > > > WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && > > - !poll_state_synchronize_rcu(oldstate), > > - "A full grace period is not passed yet: %lu", > > - rcu_seq_diff(get_state_synchronize_rcu(), oldstate)); > > + !poll_state_synchronize_rcu_full(&rs->oldstate), > > + "A full grace period is not passed yet!\n"); > > Looks good, but why not also continue printing out the required > grace-period sequence number? Yes, there would need to be helper > sprintf()-style functions to paper over the difference between Tiny RCU > and Tree RCU. ;-) > Uhh :) Do we have rcu_seq_diff() for a _full() API? Looks like not :) It contains both, rgos_norm and rgos_exp! Take a delta of both? -- Uladzislau Rezki
On Fri, Jan 24, 2025 at 12:48:12PM +0100, Uladzislau Rezki wrote: > On Thu, Jan 23, 2025 at 01:52:57PM -0800, Paul E. McKenney wrote: > > On Thu, Jan 23, 2025 at 07:58:28PM +0100, Uladzislau Rezki (Sony) wrote: > > > Switch for using of get_state_synchronize_rcu_full() and > > > poll_state_synchronize_rcu_full() pair for debug a normal > > > synchronize_rcu() call. > > > > > > Just using "not" full APIs to identify if a grace period > > > is passed or not might lead to a false kernel splat. > > > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > > > --- > > > include/linux/rcupdate_wait.h | 4 ++++ > > > kernel/rcu/tree.c | 8 +++----- > > > 2 files changed, 7 insertions(+), 5 deletions(-) > > > > > > diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h > > > index f9bed3d3f78d..a16fc2a9a7d7 100644 > > > --- a/include/linux/rcupdate_wait.h > > > +++ b/include/linux/rcupdate_wait.h > > > @@ -16,6 +16,10 @@ > > > struct rcu_synchronize { > > > struct rcu_head head; > > > struct completion completion; > > > +#ifdef CONFIG_PROVE_RCU > > > + /* This is for testing. */ > > > + struct rcu_gp_oldstate oldstate; > > > +#endif > > > }; > > > void wakeme_after_rcu(struct rcu_head *head); > > > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > > index 2795d6b5109c..0ae90089ef09 100644 > > > --- a/kernel/rcu/tree.c > > > +++ b/kernel/rcu/tree.c > > > @@ -1612,12 +1612,10 @@ static void rcu_sr_normal_complete(struct llist_node *node) > > > { > > > struct rcu_synchronize *rs = container_of( > > > (struct rcu_head *) node, struct rcu_synchronize, head); > > > - unsigned long oldstate = (unsigned long) rs->head.func; > > > > > > WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && > > > - !poll_state_synchronize_rcu(oldstate), > > > - "A full grace period is not passed yet: %lu", > > > - rcu_seq_diff(get_state_synchronize_rcu(), oldstate)); > > > + !poll_state_synchronize_rcu_full(&rs->oldstate), > > > + "A full grace period is not passed yet!\n"); > > > > Looks good, but why not also continue printing out the required > > grace-period sequence number? Yes, there would need to be helper > > sprintf()-style functions to paper over the difference between Tiny RCU > > and Tree RCU. ;-) > > > Uhh :) Do we have rcu_seq_diff() for a _full() API? Looks like not :) > > It contains both, rgos_norm and rgos_exp! Take a delta of both? Why not? Maybe separate the two differences with a colon. Or maybe make a variant of poll_state_synchronize_rcu_full() that take a char* argument, which uses the same value for the check and the string to be output. Thanx, Paul
diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h index f9bed3d3f78d..a16fc2a9a7d7 100644 --- a/include/linux/rcupdate_wait.h +++ b/include/linux/rcupdate_wait.h @@ -16,6 +16,10 @@ struct rcu_synchronize { struct rcu_head head; struct completion completion; +#ifdef CONFIG_PROVE_RCU + /* This is for testing. */ + struct rcu_gp_oldstate oldstate; +#endif }; void wakeme_after_rcu(struct rcu_head *head); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2795d6b5109c..0ae90089ef09 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1612,12 +1612,10 @@ static void rcu_sr_normal_complete(struct llist_node *node) { struct rcu_synchronize *rs = container_of( (struct rcu_head *) node, struct rcu_synchronize, head); - unsigned long oldstate = (unsigned long) rs->head.func; WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && - !poll_state_synchronize_rcu(oldstate), - "A full grace period is not passed yet: %lu", - rcu_seq_diff(get_state_synchronize_rcu(), oldstate)); + !poll_state_synchronize_rcu_full(&rs->oldstate), + "A full grace period is not passed yet!\n"); /* Finally. */ complete(&rs->completion); @@ -3214,7 +3212,7 @@ static void synchronize_rcu_normal(void) * snapshot before adding a request. */ if (IS_ENABLED(CONFIG_PROVE_RCU)) - rs.head.func = (void *) get_state_synchronize_rcu(); + get_state_synchronize_rcu_full(&rs.oldstate); rcu_sr_normal_add_req(&rs);
Switch for using of get_state_synchronize_rcu_full() and poll_state_synchronize_rcu_full() pair for debug a normal synchronize_rcu() call. Just using "not" full APIs to identify if a grace period is passed or not might lead to a false kernel splat. Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> --- include/linux/rcupdate_wait.h | 4 ++++ kernel/rcu/tree.c | 8 +++----- 2 files changed, 7 insertions(+), 5 deletions(-)