48 lines
1.9 KiB
Diff
48 lines
1.9 KiB
Diff
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Fri, 4 Aug 2023 13:30:39 +0200
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Subject: [PATCH 3/3] time: Allow to preempt after a callback.
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz
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The TIMER_SOFTIRQ handler invokes timer callbacks of the expired timers.
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Before each invocation the timer_base::lock is dropped. The only lock
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that is still held is the timer_base::expiry_lock and the per-CPU
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bh-lock as part of local_bh_disable(). The former is released as part
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of lock up prevention if the timer is preempted by the caller which is
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waiting for its completion.
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Both locks are already released as part of timer_sync_wait_running().
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This can be extended by also releasing in bh-lock. The timer core does
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not rely on any state that is serialized by the bh-lock. The timer
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callback expects the bh-state to be serialized by the lock but there is
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no need to keep state synchronized while invoking multiple callbacks.
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Preempt handling softirqs and release all locks after a timer invocation
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if the current has inherited priority.
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Link: https://lore.kernel.org/r/20230804113039.419794-4-bigeasy@linutronix.de
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/time/timer.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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--- a/kernel/time/timer.c
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+++ b/kernel/time/timer.c
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@@ -1564,9 +1564,16 @@ static void timer_sync_wait_running(stru
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__releases(&base->lock) __releases(&base->expiry_lock)
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__acquires(&base->expiry_lock) __acquires(&base->lock)
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{
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- if (atomic_read(&base->timer_waiters)) {
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+ bool need_preempt;
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+
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+ need_preempt = task_is_pi_boosted(current);
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+ if (need_preempt || atomic_read(&base->timer_waiters)) {
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raw_spin_unlock_irq(&base->lock);
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spin_unlock(&base->expiry_lock);
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+
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+ if (need_preempt)
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+ softirq_preempt();
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+
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spin_lock(&base->expiry_lock);
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raw_spin_lock_irq(&base->lock);
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}
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