diff options
| author | Frederic Weisbecker <frederic@kernel.org> | 2021-10-19 02:08:15 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-05-12 12:25:45 +0200 |
| commit | a22d66eb518f444bd66b38dbf8235d98e40f37e1 (patch) | |
| tree | 03a532f15b644e9414423aa5c2945db9b7f4cd36 /kernel | |
| parent | 40fb3812d99746f0322ada92fdc8d904a024e6de (diff) | |
rcu: Apply callbacks processing time limit only on softirq
commit a554ba288845fd3f6f12311fd76a51694233458a upstream.
Time limit only makes sense when callbacks are serviced in softirq mode
because:
_ In case we need to get back to the scheduler,
cond_resched_tasks_rcu_qs() is called after each callback.
_ In case some other softirq vector needs the CPU, the call to
local_bh_enable() before cond_resched_tasks_rcu_qs() takes care about
them via a call to do_softirq().
Therefore, make sure the time limit only applies to softirq mode.
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[UR: backport to 5.10-stable]
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/tree.c | 26 |
1 files changed, 13 insertions, 13 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f340df6ebd86..b41009a283ca 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2456,7 +2456,7 @@ static void rcu_do_batch(struct rcu_data *rdp) div = READ_ONCE(rcu_divisor); div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div; bl = max(rdp->blimit, pending >> div); - if (unlikely(bl > 100)) { + if (in_serving_softirq() && unlikely(bl > 100)) { long rrn = READ_ONCE(rcu_resched_ns); rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn; @@ -2494,6 +2494,18 @@ static void rcu_do_batch(struct rcu_data *rdp) if (-rcl.len >= bl && (need_resched() || (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) break; + + /* + * Make sure we don't spend too much time here and deprive other + * softirq vectors of CPU cycles. + */ + if (unlikely(tlimit)) { + /* only call local_clock() every 32 callbacks */ + if (likely((-rcl.len & 31) || local_clock() < tlimit)) + continue; + /* Exceeded the time limit, so leave. */ + break; + } } else { local_bh_enable(); lockdep_assert_irqs_enabled(); @@ -2501,18 +2513,6 @@ static void rcu_do_batch(struct rcu_data *rdp) lockdep_assert_irqs_enabled(); local_bh_disable(); } - - /* - * Make sure we don't spend too much time here and deprive other - * softirq vectors of CPU cycles. - */ - if (unlikely(tlimit)) { - /* only call local_clock() every 32 callbacks */ - if (likely((-rcl.len & 31) || local_clock() < tlimit)) - continue; - /* Exceeded the time limit, so leave. */ - break; - } } local_irq_save(flags); |