| Message ID | 20220512030442.2530552-13-joel@joelfernandes.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Implement call_rcu_lazy() and miscellaneous fixes | expand |
> monitor_todo is not needed as the work struct already tracks if work is > pending. Just use that to know if work is pending using > delayed_work_pending() helper. > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > --- > kernel/rcu/tree.c | 22 +++++++--------------- > 1 file changed, 7 insertions(+), 15 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 3baf29014f86..3828ac3bf1c4 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3155,7 +3155,6 @@ struct kfree_rcu_cpu_work { > * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period > * @lock: Synchronize access to this structure > * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES > - * @monitor_todo: Tracks whether a @monitor_work delayed work is pending > * @initialized: The @rcu_work fields have been initialized > * @count: Number of objects for which GP not started > * @bkvcache: > @@ -3180,7 +3179,6 @@ struct kfree_rcu_cpu { > struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES]; > raw_spinlock_t lock; > struct delayed_work monitor_work; > - bool monitor_todo; > bool initialized; > int count; > > @@ -3416,9 +3414,7 @@ static void kfree_rcu_monitor(struct work_struct *work) > // of the channels that is still busy we should rearm the > // work to repeat an attempt. Because previous batches are > // still in progress. > - if (!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) > - krcp->monitor_todo = false; > - else > + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); > > raw_spin_unlock_irqrestore(&krcp->lock, flags); > @@ -3607,10 +3603,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > // Set timer to drain after KFREE_DRAIN_JIFFIES. > if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && > - !krcp->monitor_todo) { > - krcp->monitor_todo = true; > + !delayed_work_pending(&krcp->monitor_work)) > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); > - } > > unlock_return: > krc_this_cpu_unlock(krcp, flags); > @@ -3685,14 +3679,12 @@ void __init kfree_rcu_scheduler_running(void) > struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); > > raw_spin_lock_irqsave(&krcp->lock, flags); > - if ((!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) || > - krcp->monitor_todo) { > - raw_spin_unlock_irqrestore(&krcp->lock, flags); > - continue; > + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) { > + if (delayed_work_pending(&krcp->monitor_work)) { > + schedule_delayed_work_on(cpu, &krcp->monitor_work, > + KFREE_DRAIN_JIFFIES); > + } > } > - krcp->monitor_todo = true; > - schedule_delayed_work_on(cpu, &krcp->monitor_work, > - KFREE_DRAIN_JIFFIES); > raw_spin_unlock_irqrestore(&krcp->lock, flags); > } > } > -- > Looks good to me from the first glance, but let me know to have a look at it more closely. -- Uladzislau Rezki
On Fri, May 13, 2022 at 04:53:05PM +0200, Uladzislau Rezki wrote: > > monitor_todo is not needed as the work struct already tracks if work is > > pending. Just use that to know if work is pending using > > delayed_work_pending() helper. > > > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > --- > > kernel/rcu/tree.c | 22 +++++++--------------- > > 1 file changed, 7 insertions(+), 15 deletions(-) > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 3baf29014f86..3828ac3bf1c4 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -3155,7 +3155,6 @@ struct kfree_rcu_cpu_work { > > * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period > > * @lock: Synchronize access to this structure > > * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES > > - * @monitor_todo: Tracks whether a @monitor_work delayed work is pending > > * @initialized: The @rcu_work fields have been initialized > > * @count: Number of objects for which GP not started > > * @bkvcache: > > @@ -3180,7 +3179,6 @@ struct kfree_rcu_cpu { > > struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES]; > > raw_spinlock_t lock; > > struct delayed_work monitor_work; > > - bool monitor_todo; > > bool initialized; > > int count; > > > > @@ -3416,9 +3414,7 @@ static void kfree_rcu_monitor(struct work_struct *work) > > // of the channels that is still busy we should rearm the > > // work to repeat an attempt. Because previous batches are > > // still in progress. > > - if (!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) > > - krcp->monitor_todo = false; > > - else > > + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) > > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); > > > > raw_spin_unlock_irqrestore(&krcp->lock, flags); > > @@ -3607,10 +3603,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > > > // Set timer to drain after KFREE_DRAIN_JIFFIES. > > if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && > > - !krcp->monitor_todo) { > > - krcp->monitor_todo = true; > > + !delayed_work_pending(&krcp->monitor_work)) > > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); > > - } > > > > unlock_return: > > krc_this_cpu_unlock(krcp, flags); > > @@ -3685,14 +3679,12 @@ void __init kfree_rcu_scheduler_running(void) > > struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); > > > > raw_spin_lock_irqsave(&krcp->lock, flags); > > - if ((!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) || > > - krcp->monitor_todo) { > > - raw_spin_unlock_irqrestore(&krcp->lock, flags); > > - continue; > > + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) { > > + if (delayed_work_pending(&krcp->monitor_work)) { > > + schedule_delayed_work_on(cpu, &krcp->monitor_work, > > + KFREE_DRAIN_JIFFIES); > > + } > > } > > - krcp->monitor_todo = true; > > - schedule_delayed_work_on(cpu, &krcp->monitor_work, > > - KFREE_DRAIN_JIFFIES); > > raw_spin_unlock_irqrestore(&krcp->lock, flags); > > } > > } > > -- > > > Looks good to me from the first glance, but let me know to have a look > at it more closely. Thanks, I appreciate it. - Joel
> On Fri, May 13, 2022 at 04:53:05PM +0200, Uladzislau Rezki wrote: > > > monitor_todo is not needed as the work struct already tracks if work is > > > pending. Just use that to know if work is pending using > > > delayed_work_pending() helper. > > > > > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > > --- > > > kernel/rcu/tree.c | 22 +++++++--------------- > > > 1 file changed, 7 insertions(+), 15 deletions(-) > > > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > > index 3baf29014f86..3828ac3bf1c4 100644 > > > --- a/kernel/rcu/tree.c > > > +++ b/kernel/rcu/tree.c > > > @@ -3155,7 +3155,6 @@ struct kfree_rcu_cpu_work { > > > * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period > > > * @lock: Synchronize access to this structure > > > * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES > > > - * @monitor_todo: Tracks whether a @monitor_work delayed work is pending > > > * @initialized: The @rcu_work fields have been initialized > > > * @count: Number of objects for which GP not started > > > * @bkvcache: > > > @@ -3180,7 +3179,6 @@ struct kfree_rcu_cpu { > > > struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES]; > > > raw_spinlock_t lock; > > > struct delayed_work monitor_work; > > > - bool monitor_todo; > > > bool initialized; > > > int count; > > > > > > @@ -3416,9 +3414,7 @@ static void kfree_rcu_monitor(struct work_struct *work) > > > // of the channels that is still busy we should rearm the > > > // work to repeat an attempt. Because previous batches are > > > // still in progress. > > > - if (!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) > > > - krcp->monitor_todo = false; > > > - else > > > + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) > Can we place those three checks into separate inline function because it is used in two places: krc_needs_offload()? > > > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); > > > > > > raw_spin_unlock_irqrestore(&krcp->lock, flags); > > > @@ -3607,10 +3603,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > > > > > // Set timer to drain after KFREE_DRAIN_JIFFIES. > > > if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && > > > - !krcp->monitor_todo) { > > > - krcp->monitor_todo = true; > > > + !delayed_work_pending(&krcp->monitor_work)) > I think checking weather it is pending or not does not make much sense. schedule_delayed_work() checks inside if the work can be queued. > > > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); > > > - } > > > > > > unlock_return: > > > krc_this_cpu_unlock(krcp, flags); > > > @@ -3685,14 +3679,12 @@ void __init kfree_rcu_scheduler_running(void) > > > struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); > > > > > > raw_spin_lock_irqsave(&krcp->lock, flags); > > > - if ((!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) || > > > - krcp->monitor_todo) { > > > - raw_spin_unlock_irqrestore(&krcp->lock, flags); > > > - continue; > > > + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) { Same here. Move to the separate function, IMHO makes sense. > > > + if (delayed_work_pending(&krcp->monitor_work)) { Same here. Should we check it here? > > > + schedule_delayed_work_on(cpu, &krcp->monitor_work, > > > + KFREE_DRAIN_JIFFIES); > > > + } > > > } > > > - krcp->monitor_todo = true; > > > - schedule_delayed_work_on(cpu, &krcp->monitor_work, > > > - KFREE_DRAIN_JIFFIES); > > > raw_spin_unlock_irqrestore(&krcp->lock, flags); > > > } > > > } > > > -- > > > > > Looks good to me from the first glance, but let me know to have a look > > at it more closely. > > Thanks, I appreciate it. > One change in design after this patch is a drain work can be queued even though there is already nothing to drain. I do not find it as a big issue because it will just bail out. So i tend to simplification. The monitor_todo guarantees that kvfree_rcu() caller will not schedule any work until "monitor work" completes its job and if there is still to do something there it rearms itself. -- Uladzsialu Rezki
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 3baf29014f86..3828ac3bf1c4 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3155,7 +3155,6 @@ struct kfree_rcu_cpu_work { * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period * @lock: Synchronize access to this structure * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES - * @monitor_todo: Tracks whether a @monitor_work delayed work is pending * @initialized: The @rcu_work fields have been initialized * @count: Number of objects for which GP not started * @bkvcache: @@ -3180,7 +3179,6 @@ struct kfree_rcu_cpu { struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES]; raw_spinlock_t lock; struct delayed_work monitor_work; - bool monitor_todo; bool initialized; int count; @@ -3416,9 +3414,7 @@ static void kfree_rcu_monitor(struct work_struct *work) // of the channels that is still busy we should rearm the // work to repeat an attempt. Because previous batches are // still in progress. - if (!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) - krcp->monitor_todo = false; - else + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); raw_spin_unlock_irqrestore(&krcp->lock, flags); @@ -3607,10 +3603,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) // Set timer to drain after KFREE_DRAIN_JIFFIES. if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && - !krcp->monitor_todo) { - krcp->monitor_todo = true; + !delayed_work_pending(&krcp->monitor_work)) schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); - } unlock_return: krc_this_cpu_unlock(krcp, flags); @@ -3685,14 +3679,12 @@ void __init kfree_rcu_scheduler_running(void) struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); raw_spin_lock_irqsave(&krcp->lock, flags); - if ((!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) || - krcp->monitor_todo) { - raw_spin_unlock_irqrestore(&krcp->lock, flags); - continue; + if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) { + if (delayed_work_pending(&krcp->monitor_work)) { + schedule_delayed_work_on(cpu, &krcp->monitor_work, + KFREE_DRAIN_JIFFIES); + } } - krcp->monitor_todo = true; - schedule_delayed_work_on(cpu, &krcp->monitor_work, - KFREE_DRAIN_JIFFIES); raw_spin_unlock_irqrestore(&krcp->lock, flags); } }
monitor_todo is not needed as the work struct already tracks if work is pending. Just use that to know if work is pending using delayed_work_pending() helper. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> --- kernel/rcu/tree.c | 22 +++++++--------------- 1 file changed, 7 insertions(+), 15 deletions(-)