Re: [PATCH 11/13] rcu/nocb: Only cancel nocb timer if not polling
On Tue, Mar 02, 2021 at 05:22:29PM -0800, Paul E. McKenney wrote: > On Tue, Feb 23, 2021 at 01:10:09AM +0100, Frederic Weisbecker wrote: > > No need to disarm the nocb_timer if rcu_nocb is polling because it > > shouldn't be armed either. > > > > Signed-off-by: Frederic Weisbecker > > Cc: Josh Triplett > > Cc: Lai Jiangshan > > Cc: Joel Fernandes > > Cc: Neeraj Upadhyay > > Cc: Boqun Feng > > OK, so it does make sense to move that del_timer() under the following > "if" statement, then. ;-) Right, probably I should have handled that in the beginning of the patchset instead of the end but heh, my mind is never that clear. Thanks.
Re: [PATCH 11/13] rcu/nocb: Only cancel nocb timer if not polling
On Tue, Feb 23, 2021 at 01:10:09AM +0100, Frederic Weisbecker wrote:
> No need to disarm the nocb_timer if rcu_nocb is polling because it
> shouldn't be armed either.
>
> Signed-off-by: Frederic Weisbecker
> Cc: Josh Triplett
> Cc: Lai Jiangshan
> Cc: Joel Fernandes
> Cc: Neeraj Upadhyay
> Cc: Boqun Feng
OK, so it does make sense to move that del_timer() under the following
"if" statement, then. ;-)
> ---
> kernel/rcu/tree_plugin.h | 14 +++---
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 9da67b0d3997..d8b50ff40e4b 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -2186,18 +2186,18 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
> my_rdp->nocb_gp_gp = needwait_gp;
> my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
> if (bypass) {
> - raw_spin_lock_irqsave(_rdp->nocb_gp_lock, flags);
> - // Avoid race with first bypass CB.
> - if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
> - WRITE_ONCE(my_rdp->nocb_defer_wakeup,
> RCU_NOCB_WAKE_NOT);
> - del_timer(_rdp->nocb_timer);
> - }
> if (!rcu_nocb_poll) {
> + raw_spin_lock_irqsave(_rdp->nocb_gp_lock, flags);
> + // Avoid race with first bypass CB.
> + if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
> + WRITE_ONCE(my_rdp->nocb_defer_wakeup,
> RCU_NOCB_WAKE_NOT);
> + del_timer(_rdp->nocb_timer);
> + }
> // At least one child with non-empty ->nocb_bypass, so
> set
> // timer in order to avoid stranding its callbacks.
> mod_timer(_rdp->nocb_bypass_timer, j + 2);
> + raw_spin_unlock_irqrestore(_rdp->nocb_gp_lock,
> flags);
> }
> - raw_spin_unlock_irqrestore(_rdp->nocb_gp_lock, flags);
> }
> if (rcu_nocb_poll) {
> /* Polling, so trace if first poll in the series. */
> --
> 2.25.1
>
[PATCH 11/13] rcu/nocb: Only cancel nocb timer if not polling
No need to disarm the nocb_timer if rcu_nocb is polling because it
shouldn't be armed either.
Signed-off-by: Frederic Weisbecker
Cc: Josh Triplett
Cc: Lai Jiangshan
Cc: Joel Fernandes
Cc: Neeraj Upadhyay
Cc: Boqun Feng
---
kernel/rcu/tree_plugin.h | 14 +++---
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 9da67b0d3997..d8b50ff40e4b 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2186,18 +2186,18 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
my_rdp->nocb_gp_gp = needwait_gp;
my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
if (bypass) {
- raw_spin_lock_irqsave(_rdp->nocb_gp_lock, flags);
- // Avoid race with first bypass CB.
- if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
- WRITE_ONCE(my_rdp->nocb_defer_wakeup,
RCU_NOCB_WAKE_NOT);
- del_timer(_rdp->nocb_timer);
- }
if (!rcu_nocb_poll) {
+ raw_spin_lock_irqsave(_rdp->nocb_gp_lock, flags);
+ // Avoid race with first bypass CB.
+ if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+ WRITE_ONCE(my_rdp->nocb_defer_wakeup,
RCU_NOCB_WAKE_NOT);
+ del_timer(_rdp->nocb_timer);
+ }
// At least one child with non-empty ->nocb_bypass, so
set
// timer in order to avoid stranding its callbacks.
mod_timer(_rdp->nocb_bypass_timer, j + 2);
+ raw_spin_unlock_irqrestore(_rdp->nocb_gp_lock,
flags);
}
- raw_spin_unlock_irqrestore(_rdp->nocb_gp_lock, flags);
}
if (rcu_nocb_poll) {
/* Polling, so trace if first poll in the series. */
--
2.25.1
