| Message ID | 20231208220545.7452-5-frederic@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | rcu: Fix expedited GP deadlock (and cleanup some nocb stuff) | expand |
On Fri, Dec 8, 2023 at 5:06 PM Frederic Weisbecker <frederic@kernel.org> wrote: > > Just like is done for the kworker performing nodes initialization, > gracefully handle the possible allocation failure of the RCU expedited > grace period main kworker. > > While at it perform a rename of the related checking functions to better > reflect the expedited specifics. > > Fixes: 9621fbee44df ("rcu: Move expedited grace period (GP) work to RT kthread_worker") > Cc: Kalesh Singh <kaleshsingh@google.com> > Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Kalesh Singh <kaleshsingh@google.com> Thanks, Kalesh > --- > kernel/rcu/tree.c | 2 ++ > kernel/rcu/tree_exp.h | 25 +++++++++++++++++++------ > 2 files changed, 21 insertions(+), 6 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 055f4817bc70..39679cf66c3a 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -4717,6 +4717,7 @@ static void __init rcu_start_exp_gp_kworkers(void) > rcu_exp_gp_kworker = kthread_create_worker(0, gp_kworker_name); > if (IS_ERR_OR_NULL(rcu_exp_gp_kworker)) { > pr_err("Failed to create %s!\n", gp_kworker_name); > + rcu_exp_gp_kworker = NULL; > return; > } > > @@ -4725,6 +4726,7 @@ static void __init rcu_start_exp_gp_kworkers(void) > pr_err("Failed to create %s!\n", par_gp_kworker_name); > rcu_exp_par_gp_kworker = NULL; > kthread_destroy_worker(rcu_exp_gp_kworker); > + rcu_exp_gp_kworker = NULL; > return; > } > > diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h > index 6d7cea5d591f..cb31f4fb4b36 100644 > --- a/kernel/rcu/tree_exp.h > +++ b/kernel/rcu/tree_exp.h > @@ -429,7 +429,12 @@ static void sync_rcu_exp_select_node_cpus(struct kthread_work *wp) > __sync_rcu_exp_select_node_cpus(rewp); > } > > -static inline bool rcu_gp_par_worker_started(void) > +static inline bool rcu_exp_worker_started(void) > +{ > + return !!READ_ONCE(rcu_exp_gp_kworker); > +} > + > +static inline bool rcu_exp_par_worker_started(void) > { > return !!READ_ONCE(rcu_exp_par_gp_kworker); > } > @@ -479,7 +484,12 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) > __sync_rcu_exp_select_node_cpus(rewp); > } > > -static inline bool rcu_gp_par_worker_started(void) > +static inline bool rcu_exp_worker_started(void) > +{ > + return !!READ_ONCE(rcu_gp_wq); > +} > + > +static inline bool rcu_exp_par_worker_started(void) > { > return !!READ_ONCE(rcu_par_gp_wq); > } > @@ -542,7 +552,7 @@ static void sync_rcu_exp_select_cpus(void) > rnp->exp_need_flush = false; > if (!READ_ONCE(rnp->expmask)) > continue; /* Avoid early boot non-existent wq. */ > - if (!rcu_gp_par_worker_started() || > + if (!rcu_exp_par_worker_started() || > rcu_scheduler_active != RCU_SCHEDULER_RUNNING || > rcu_is_last_leaf_node(rnp)) { > /* No worker started yet or last leaf, do direct call. */ > @@ -957,7 +967,7 @@ static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp) > */ > void synchronize_rcu_expedited(void) > { > - bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT); > + bool can_queue; > unsigned long flags; > struct rcu_exp_work rew; > struct rcu_node *rnp; > @@ -968,6 +978,9 @@ void synchronize_rcu_expedited(void) > lock_is_held(&rcu_sched_lock_map), > "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); > > + can_queue = (rcu_scheduler_active != RCU_SCHEDULER_INIT) && > + rcu_exp_worker_started(); > + > /* Is the state is such that the call is a grace period? */ > if (rcu_blocking_is_gp()) { > // Note well that this code runs with !PREEMPT && !SMP. > @@ -997,7 +1010,7 @@ void synchronize_rcu_expedited(void) > return; /* Someone else did our work for us. */ > > /* Ensure that load happens before action based on it. */ > - if (unlikely(boottime)) { > + if (unlikely(!can_queue)) { > /* Direct call during scheduler init and early_initcalls(). */ > rcu_exp_sel_wait_wake(s); > } else { > @@ -1015,7 +1028,7 @@ void synchronize_rcu_expedited(void) > /* Let the next expedited grace period start. */ > mutex_unlock(&rcu_state.exp_mutex); > > - if (likely(!boottime)) > + if (likely(can_queue)) > synchronize_rcu_expedited_destroy_work(&rew); > } > EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); > -- > 2.42.1 >
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 055f4817bc70..39679cf66c3a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4717,6 +4717,7 @@ static void __init rcu_start_exp_gp_kworkers(void) rcu_exp_gp_kworker = kthread_create_worker(0, gp_kworker_name); if (IS_ERR_OR_NULL(rcu_exp_gp_kworker)) { pr_err("Failed to create %s!\n", gp_kworker_name); + rcu_exp_gp_kworker = NULL; return; } @@ -4725,6 +4726,7 @@ static void __init rcu_start_exp_gp_kworkers(void) pr_err("Failed to create %s!\n", par_gp_kworker_name); rcu_exp_par_gp_kworker = NULL; kthread_destroy_worker(rcu_exp_gp_kworker); + rcu_exp_gp_kworker = NULL; return; } diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 6d7cea5d591f..cb31f4fb4b36 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -429,7 +429,12 @@ static void sync_rcu_exp_select_node_cpus(struct kthread_work *wp) __sync_rcu_exp_select_node_cpus(rewp); } -static inline bool rcu_gp_par_worker_started(void) +static inline bool rcu_exp_worker_started(void) +{ + return !!READ_ONCE(rcu_exp_gp_kworker); +} + +static inline bool rcu_exp_par_worker_started(void) { return !!READ_ONCE(rcu_exp_par_gp_kworker); } @@ -479,7 +484,12 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) __sync_rcu_exp_select_node_cpus(rewp); } -static inline bool rcu_gp_par_worker_started(void) +static inline bool rcu_exp_worker_started(void) +{ + return !!READ_ONCE(rcu_gp_wq); +} + +static inline bool rcu_exp_par_worker_started(void) { return !!READ_ONCE(rcu_par_gp_wq); } @@ -542,7 +552,7 @@ static void sync_rcu_exp_select_cpus(void) rnp->exp_need_flush = false; if (!READ_ONCE(rnp->expmask)) continue; /* Avoid early boot non-existent wq. */ - if (!rcu_gp_par_worker_started() || + if (!rcu_exp_par_worker_started() || rcu_scheduler_active != RCU_SCHEDULER_RUNNING || rcu_is_last_leaf_node(rnp)) { /* No worker started yet or last leaf, do direct call. */ @@ -957,7 +967,7 @@ static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp) */ void synchronize_rcu_expedited(void) { - bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT); + bool can_queue; unsigned long flags; struct rcu_exp_work rew; struct rcu_node *rnp; @@ -968,6 +978,9 @@ void synchronize_rcu_expedited(void) lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); + can_queue = (rcu_scheduler_active != RCU_SCHEDULER_INIT) && + rcu_exp_worker_started(); + /* Is the state is such that the call is a grace period? */ if (rcu_blocking_is_gp()) { // Note well that this code runs with !PREEMPT && !SMP. @@ -997,7 +1010,7 @@ void synchronize_rcu_expedited(void) return; /* Someone else did our work for us. */ /* Ensure that load happens before action based on it. */ - if (unlikely(boottime)) { + if (unlikely(!can_queue)) { /* Direct call during scheduler init and early_initcalls(). */ rcu_exp_sel_wait_wake(s); } else { @@ -1015,7 +1028,7 @@ void synchronize_rcu_expedited(void) /* Let the next expedited grace period start. */ mutex_unlock(&rcu_state.exp_mutex); - if (likely(!boottime)) + if (likely(can_queue)) synchronize_rcu_expedited_destroy_work(&rew); } EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
Just like is done for the kworker performing nodes initialization, gracefully handle the possible allocation failure of the RCU expedited grace period main kworker. While at it perform a rename of the related checking functions to better reflect the expedited specifics. Fixes: 9621fbee44df ("rcu: Move expedited grace period (GP) work to RT kthread_worker") Cc: Kalesh Singh <kaleshsingh@google.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> --- kernel/rcu/tree.c | 2 ++ kernel/rcu/tree_exp.h | 25 +++++++++++++++++++------ 2 files changed, 21 insertions(+), 6 deletions(-)