| Message ID | 20250224133659.879074-3-urezki@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2,1/3] rcutorture: Allow a negative value for nfakewriters | expand |
On Mon, Feb 24, 2025 at 02:36:59PM +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. > > Link: https://lore.kernel.org/lkml/Z5ikQeVmVdsWQrdD@pc636/T/ > Fixes: 988f569ae041 ("rcu: Reduce synchronize_rcu() latency") > Reported-by: cheung wall <zzqq0103.hey@gmail.com> > 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 This causes the build to fail on TREE01. One way to make the build succeed is to remove the #ifdefs above. Another way would be to add #ifdefs to the WARN_ONCE() below. I suspect that removing the #ifdefs is best, at least until such time as people start passing many tens of SRCU instances to synchronize_rcu_mult() or some such (which seems quite unlikely). Thoughts? Thanx, Paul > }; > void wakeme_after_rcu(struct rcu_head *head); > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 8625f616c65a..48384fa2eaeb 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1632,12 +1632,10 @@ 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); > @@ -3247,7 +3245,7 @@ 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 Mon, Feb 24, 2025 at 11:06:01AM -0800, Paul E. McKenney wrote: > On Mon, Feb 24, 2025 at 02:36:59PM +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. > > > > Link: https://lore.kernel.org/lkml/Z5ikQeVmVdsWQrdD@pc636/T/ > > Fixes: 988f569ae041 ("rcu: Reduce synchronize_rcu() latency") > > Reported-by: cheung wall <zzqq0103.hey@gmail.com> > > 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 > > This causes the build to fail on TREE01. One way to make the build > succeed is to remove the #ifdefs above. Another way would be to add > #ifdefs to the WARN_ONCE() below. I suspect that removing the #ifdefs > is best, at least until such time as people start passing many tens > of SRCU instances to synchronize_rcu_mult() or some such (which seems > quite unlikely). > > Thoughts? > Right, i agree. I will repost this series. Thank you for checking and testing :) -- Uladzislau Rezki
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 8625f616c65a..48384fa2eaeb 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1632,12 +1632,10 @@ 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); @@ -3247,7 +3245,7 @@ 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. Link: https://lore.kernel.org/lkml/Z5ikQeVmVdsWQrdD@pc636/T/ Fixes: 988f569ae041 ("rcu: Reduce synchronize_rcu() latency") Reported-by: cheung wall <zzqq0103.hey@gmail.com> 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(-)