diff options
| author |   Paul E. McKenney <paulmck@kernel.org> | 2019-08-15 13:24:49 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2019-10-28 07:02:21 -0700 |
| commit | b200a0489517d9e5a52e983183e890f573454ebd (patch) | |
| tree | 915a0acac938aaa4252741550c7fa380efdf67dc /kernel/rcu | |
| parent | rcu: Force tick on for nohz_full CPUs not reaching quiescent states (diff) | |
| download | linux-dev-b200a0489517d9e5a52e983183e890f573454ebd.tar.xz linux-dev-b200a0489517d9e5a52e983183e890f573454ebd.zip | |
rcu: Force nohz_full tick on upon irq enter instead of exit
There is interrupt-exit code that forces on the tick for nohz_full CPUs
failing to respond to the current grace period in a timely fashion.
However, this code must compare ->dynticks_nmi_nesting to the value 2
in the interrupt-exit fastpath. This commit therefore moves this code
to the interrupt-entry fastpath, where a lighter-weight comparison to
zero may be used.
Reported-by: Joel Fernandes <joel@joelfernandes.org>
[ paulmck: Apply Joel Fernandes TICK_DEP_MASK_RCU->TICK_DEP_BIT_RCU fix. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 9fda33864ede..8dc878406c71 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -651,12 +651,6 @@ static __always_inline void rcu_nmi_exit_common(bool irq) */ if (rdp->dynticks_nmi_nesting != 1) { trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks); - if (tick_nohz_full_cpu(rdp->cpu) && - rdp->dynticks_nmi_nesting == 2 && - rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { - rdp->rcu_forced_tick = true; - tick_dep_set_cpu(rdp->cpu, TICK_DEP_MASK_RCU); - } WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ rdp->dynticks_nmi_nesting - 2); return; @@ -831,6 +825,11 @@ static __always_inline void rcu_nmi_enter_common(bool irq) rcu_cleanup_after_idle(); incby = 1; + } else if (tick_nohz_full_cpu(rdp->cpu) && + rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE && + rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { + rdp->rcu_forced_tick = true; + tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU); } trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), rdp->dynticks_nmi_nesting, |