On Thu, Feb 27, 2025 at 09:12:39AM -0800, Boqun Feng wrote: > Hi Ulad, > > I put these three patches into next (and misc.2025.02.27a) for some > testing, hopefully it all goes well and they can make it v6.15. > > A few tag changed below: > > On Thu, Feb 27, 2025 at 02:16:13PM +0100, Uladzislau Rezki (Sony) wrote: > > Switch for using of get_state_synchronize_rcu_full() and > > poll_state_synchronize_rcu_full() pair to 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-positive kernel splat. > > > > It can happen, because get_state_synchronize_rcu() compresses > > both normal and expedited states into one single unsigned long > > value, so a poll_state_synchronize_rcu() can miss GP-completion > > when synchronize_rcu()/synchronize_rcu_expedited() concurrently > > run. > > > > To address this, switch to poll_state_synchronize_rcu_full() and > > get_state_synchronize_rcu_full() APIs, which use separate variables > > for expedited and normal states. > > > > Link: https://lore.kernel.org/lkml/Z5ikQeVmVdsWQrdD@pc636/T/ > > I switch this into "Closes:" per checkpatch. > > > Fixes: 988f569ae041 ("rcu: Reduce synchronize_rcu() latency") > > Reported-by: cheung wall <zzqq0103.hey@xxxxxxxxx> > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> > > You seem to forget add Paul's Reviewed-by, so I add it in rcu/next. > Would you or Paul double-check the Reviewed-by should be here? I am good with keeping my Reviewed-by tags. Thanx, Paul > Regards, > Boqun > > > --- > > include/linux/rcupdate_wait.h | 3 +++ > > kernel/rcu/tree.c | 8 +++----- > > 2 files changed, 6 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h > > index f9bed3d3f78d..4c92d4291cce 100644 > > --- a/include/linux/rcupdate_wait.h > > +++ b/include/linux/rcupdate_wait.h > > @@ -16,6 +16,9 @@ > > struct rcu_synchronize { > > struct rcu_head head; > > struct completion completion; > > + > > + /* This is for debugging. */ > > + struct rcu_gp_oldstate oldstate; > > }; > > 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 > >
