| Message ID | 20210223001011.127063-12-frederic@kernel.org |
|---|---|
| State | Accepted |
| Commit | f9fc166b790bd214083035d865653133b8a963d1 |
| Headers | show |
| Series | rcu/nocb updates v2 | expand |
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 <frederic@kernel.org> > Cc: Josh Triplett <josh@joshtriplett.org> > Cc: Lai Jiangshan <jiangshanlai@gmail.com> > Cc: Joel Fernandes <joel@joelfernandes.org> > Cc: Neeraj Upadhyay <neeraju@codeaurora.org> > Cc: Boqun Feng <boqun.feng@gmail.com> 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(&my_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(&my_rdp->nocb_timer); > - } > if (!rcu_nocb_poll) { > + raw_spin_lock_irqsave(&my_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(&my_rdp->nocb_timer); > + } > // At least one child with non-empty ->nocb_bypass, so set > // timer in order to avoid stranding its callbacks. > mod_timer(&my_rdp->nocb_bypass_timer, j + 2); > + raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags); > } > - raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags); > } > if (rcu_nocb_poll) { > /* Polling, so trace if first poll in the series. */ > -- > 2.25.1 >
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 <frederic@kernel.org> > > Cc: Josh Triplett <josh@joshtriplett.org> > > Cc: Lai Jiangshan <jiangshanlai@gmail.com> > > Cc: Joel Fernandes <joel@joelfernandes.org> > > Cc: Neeraj Upadhyay <neeraju@codeaurora.org> > > Cc: Boqun Feng <boqun.feng@gmail.com> > > 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.
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(&my_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(&my_rdp->nocb_timer); - } if (!rcu_nocb_poll) { + raw_spin_lock_irqsave(&my_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(&my_rdp->nocb_timer); + } // At least one child with non-empty ->nocb_bypass, so set // timer in order to avoid stranding its callbacks. mod_timer(&my_rdp->nocb_bypass_timer, j + 2); + raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags); } - raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags); } if (rcu_nocb_poll) { /* Polling, so trace if first poll in the series. */
No need to disarm the nocb_timer if rcu_nocb is polling because it shouldn't be armed either. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Neeraj Upadhyay <neeraju@codeaurora.org> Cc: Boqun Feng <boqun.feng@gmail.com> --- kernel/rcu/tree_plugin.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)