diff options
Diffstat (limited to 'debian/patches-rt/0013-rcutorture-Also-force-sched-priority-to-timersd-on-b.patch')
| -rw-r--r-- | debian/patches-rt/0013-rcutorture-Also-force-sched-priority-to-timersd-on-b.patch | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/debian/patches-rt/0013-rcutorture-Also-force-sched-priority-to-timersd-on-b.patch b/debian/patches-rt/0013-rcutorture-Also-force-sched-priority-to-timersd-on-b.patch new file mode 100644 index 000000000..9e062b97c --- /dev/null +++ b/debian/patches-rt/0013-rcutorture-Also-force-sched-priority-to-timersd-on-b.patch @@ -0,0 +1,81 @@ +From a10aa54ef224bbd46ca1777e4b9fe960360961cc Mon Sep 17 00:00:00 2001 +From: Frederic Weisbecker <frederic@kernel.org> +Date: Tue, 5 Apr 2022 03:07:51 +0200 +Subject: [PATCH 13/62] rcutorture: Also force sched priority to timersd on + boosting test. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.1/older/patches-6.1.69-rt21.tar.xz + +ksoftirqd is statically boosted to the priority level right above the +one of rcu_torture_boost() so that timers, which torture readers rely on, +get a chance to run while rcu_torture_boost() is polling. + +However timers processing got split from ksoftirqd into their own kthread +(timersd) that isn't boosted. It has the same SCHED_FIFO low prio as +rcu_torture_boost() and therefore timers can't preempt it and may +starve. + +The issue can be triggered in practice on v5.17.1-rt17 using: + + ./kvm.sh --allcpus --configs TREE04 --duration 10m --kconfig "CONFIG_EXPERT=y CONFIG_PREEMPT_RT=y" + +Fix this with statically boosting timersd just like is done with +ksoftirqd in commit + ea6d962e80b61 ("rcutorture: Judge RCU priority boosting on grace periods, not callbacks") + +Suggested-by: Mel Gorman <mgorman@suse.de> +Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Cc: Thomas Gleixner <tglx@linutronix.de> +Signed-off-by: Frederic Weisbecker <frederic@kernel.org> +Link: https://lkml.kernel.org/r/20220405010752.1347437-1-frederic@kernel.org +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/interrupt.h | 1 + + kernel/rcu/rcutorture.c | 6 ++++++ + kernel/softirq.c | 2 +- + 3 files changed, 8 insertions(+), 1 deletion(-) + +diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h +index 0efba74a835c..f459b0f27c94 100644 +--- a/include/linux/interrupt.h ++++ b/include/linux/interrupt.h +@@ -610,6 +610,7 @@ extern void raise_softirq_irqoff(unsigned int nr); + extern void raise_softirq(unsigned int nr); + + #ifdef CONFIG_PREEMPT_RT ++DECLARE_PER_CPU(struct task_struct *, timersd); + extern void raise_timer_softirq(void); + extern void raise_hrtimer_softirq(void); + +diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c +index 503c2aa845a4..dcd8c0e44c00 100644 +--- a/kernel/rcu/rcutorture.c ++++ b/kernel/rcu/rcutorture.c +@@ -2363,6 +2363,12 @@ static int rcutorture_booster_init(unsigned int cpu) + WARN_ON_ONCE(!t); + sp.sched_priority = 2; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); ++#ifdef CONFIG_PREEMPT_RT ++ t = per_cpu(timersd, cpu); ++ WARN_ON_ONCE(!t); ++ sp.sched_priority = 2; ++ sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); ++#endif + } + + /* Don't allow time recalculation while creating a new task. */ +diff --git a/kernel/softirq.c b/kernel/softirq.c +index ed6d7c41aa17..1892af494cdd 100644 +--- a/kernel/softirq.c ++++ b/kernel/softirq.c +@@ -638,7 +638,7 @@ static inline void tick_irq_exit(void) + } + + #ifdef CONFIG_PREEMPT_RT +-static DEFINE_PER_CPU(struct task_struct *, timersd); ++DEFINE_PER_CPU(struct task_struct *, timersd); + static DEFINE_PER_CPU(unsigned long, pending_timer_softirq); + + static unsigned int local_pending_timers(void) +-- +2.43.0 + |