diff options
Diffstat (limited to 'features/rt/tick-sched-Prevent-false-positive-softirq-pending-wa.patch')
| -rw-r--r-- | features/rt/tick-sched-Prevent-false-positive-softirq-pending-wa.patch | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/features/rt/tick-sched-Prevent-false-positive-softirq-pending-wa.patch b/features/rt/tick-sched-Prevent-false-positive-softirq-pending-wa.patch new file mode 100644 index 00000000..fdb4a427 --- /dev/null +++ b/features/rt/tick-sched-Prevent-false-positive-softirq-pending-wa.patch @@ -0,0 +1,83 @@ +From 571cd3959f5bd78c55407d18eeb3b1f39d62aac2 Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner <tglx@linutronix.de> +Date: Tue, 9 Mar 2021 09:55:57 +0100 +Subject: [PATCH 059/191] tick/sched: Prevent false positive softirq pending + warnings on RT + +On RT a task which has soft interrupts disabled can block on a lock and +schedule out to idle while soft interrupts are pending. This triggers the +warning in the NOHZ idle code which complains about going idle with pending +soft interrupts. But as the task is blocked soft interrupt processing is +temporarily blocked as well which means that such a warning is a false +positive. + +To prevent that check the per CPU state which indicates that a scheduled +out task has soft interrupts disabled. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Reviewed-by: Frederic Weisbecker <frederic@kernel.org> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/bottom_half.h | 6 ++++++ + kernel/softirq.c | 15 +++++++++++++++ + kernel/time/tick-sched.c | 2 +- + 3 files changed, 22 insertions(+), 1 deletion(-) + +diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h +index e4dd613a070e..eed86eb0a1de 100644 +--- a/include/linux/bottom_half.h ++++ b/include/linux/bottom_half.h +@@ -32,4 +32,10 @@ static inline void local_bh_enable(void) + __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); + } + ++#ifdef CONFIG_PREEMPT_RT ++extern bool local_bh_blocked(void); ++#else ++static inline bool local_bh_blocked(void) { return false; } ++#endif ++ + #endif /* _LINUX_BH_H */ +diff --git a/kernel/softirq.c b/kernel/softirq.c +index 54fd7cc97a4a..4e9077577043 100644 +--- a/kernel/softirq.c ++++ b/kernel/softirq.c +@@ -141,6 +141,21 @@ static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = { + .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock), + }; + ++/** ++ * local_bh_blocked() - Check for idle whether BH processing is blocked ++ * ++ * Returns false if the per CPU softirq::cnt is 0 otherwise true. ++ * ++ * This is invoked from the idle task to guard against false positive ++ * softirq pending warnings, which would happen when the task which holds ++ * softirq_ctrl::lock was the only running task on the CPU and blocks on ++ * some other lock. ++ */ ++bool local_bh_blocked(void) ++{ ++ return __this_cpu_read(softirq_ctrl.cnt) != 0; ++} ++ + void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) + { + unsigned long flags; +diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c +index e10a4af88737..0cc55791b2b6 100644 +--- a/kernel/time/tick-sched.c ++++ b/kernel/time/tick-sched.c +@@ -973,7 +973,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) + if (unlikely(local_softirq_pending())) { + static int ratelimit; + +- if (ratelimit < 10 && ++ if (ratelimit < 10 && !local_bh_blocked() && + (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { + pr_warn("NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%02x!!!\n", + (unsigned int) local_softirq_pending()); +-- +2.19.1 + |