| Message ID | 20240429173439.1685274-1-mmpgouride@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | rcu: Remove unreachable logic | expand |
On 2024-04-29 13:34, Alan Huang wrote: > call_rcu_core is only called from __call_rcu_common with interrupt > disabled. This patch thus removes the unreachable logic and the would-be > unused 'flags' parameter. Nack. call_rcu_core() receives a @flags parameter which are the _saved_ flags as they were prior to local_irq_save(). This patch highlights a misunderstanding of what the code is actually doing. Thanks, Mathieu > > Signed-off-by: Alan Huang <mmpgouride@gmail.com> > --- > kernel/rcu/tree.c | 35 ++--------------------------------- > 1 file changed, 2 insertions(+), 33 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index d5507ac1bbf1..b0ea2ebd7769 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2983,7 +2983,7 @@ static void rcutree_enqueue(struct rcu_data *rdp, struct rcu_head *head, rcu_cal > * Handle any core-RCU processing required by a call_rcu() invocation. > */ > static void call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, > - rcu_callback_t func, unsigned long flags) > + rcu_callback_t func) > { > rcutree_enqueue(rdp, head, func); > /* > @@ -2992,37 +2992,6 @@ static void call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, > */ > if (!rcu_is_watching()) > invoke_rcu_core(); > - > - /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ > - if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) > - return; > - > - /* > - * Force the grace period if too many callbacks or too long waiting. > - * Enforce hysteresis, and don't invoke rcu_force_quiescent_state() > - * if some other CPU has recently done so. Also, don't bother > - * invoking rcu_force_quiescent_state() if the newly enqueued callback > - * is the only one waiting for a grace period to complete. > - */ > - if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > > - rdp->qlen_last_fqs_check + qhimark)) { > - > - /* Are we ignoring a completed grace period? */ > - note_gp_changes(rdp); > - > - /* Start a new grace period if one not already started. */ > - if (!rcu_gp_in_progress()) { > - rcu_accelerate_cbs_unlocked(rdp->mynode, rdp); > - } else { > - /* Give the grace period a kick. */ > - rdp->blimit = DEFAULT_MAX_RCU_BLIMIT; > - if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap && > - rcu_segcblist_first_pend_cb(&rdp->cblist) != head) > - rcu_force_quiescent_state(); > - rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs); > - rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); > - } > - } > } > > /* > @@ -3121,7 +3090,7 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in) > if (unlikely(rcu_rdp_is_offloaded(rdp))) > call_rcu_nocb(rdp, head, func, flags, lazy); > else > - call_rcu_core(rdp, head, func, flags); > + call_rcu_core(rdp, head, func); > local_irq_restore(flags); > } >
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d5507ac1bbf1..b0ea2ebd7769 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2983,7 +2983,7 @@ static void rcutree_enqueue(struct rcu_data *rdp, struct rcu_head *head, rcu_cal * Handle any core-RCU processing required by a call_rcu() invocation. */ static void call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, - rcu_callback_t func, unsigned long flags) + rcu_callback_t func) { rcutree_enqueue(rdp, head, func); /* @@ -2992,37 +2992,6 @@ static void call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, */ if (!rcu_is_watching()) invoke_rcu_core(); - - /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ - if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) - return; - - /* - * Force the grace period if too many callbacks or too long waiting. - * Enforce hysteresis, and don't invoke rcu_force_quiescent_state() - * if some other CPU has recently done so. Also, don't bother - * invoking rcu_force_quiescent_state() if the newly enqueued callback - * is the only one waiting for a grace period to complete. - */ - if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > - rdp->qlen_last_fqs_check + qhimark)) { - - /* Are we ignoring a completed grace period? */ - note_gp_changes(rdp); - - /* Start a new grace period if one not already started. */ - if (!rcu_gp_in_progress()) { - rcu_accelerate_cbs_unlocked(rdp->mynode, rdp); - } else { - /* Give the grace period a kick. */ - rdp->blimit = DEFAULT_MAX_RCU_BLIMIT; - if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap && - rcu_segcblist_first_pend_cb(&rdp->cblist) != head) - rcu_force_quiescent_state(); - rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs); - rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); - } - } } /* @@ -3121,7 +3090,7 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in) if (unlikely(rcu_rdp_is_offloaded(rdp))) call_rcu_nocb(rdp, head, func, flags, lazy); else - call_rcu_core(rdp, head, func, flags); + call_rcu_core(rdp, head, func); local_irq_restore(flags); }
call_rcu_core is only called from __call_rcu_common with interrupt disabled. This patch thus removes the unreachable logic and the would-be unused 'flags' parameter. Signed-off-by: Alan Huang <mmpgouride@gmail.com> --- kernel/rcu/tree.c | 35 ++--------------------------------- 1 file changed, 2 insertions(+), 33 deletions(-)