From f4cdf0cfa15d960306da4979205e6b60b6add02f Mon Sep 17 00:00:00 2001 From: zr_yy Date: Mon, 5 Jun 2023 11:55:53 +0800 Subject: [PATCH 1/2] softirq: Add RT specific softirq accounting commit f0ac2af783811a9dd6fc002cc975bf6e7bba96f2 upstream. RT requires the softirq processing and local bottomhalf disabled regions to be preemptible. Using the normal preempt count based serialization is therefore not possible because this implicitely disables preemption. RT kernels use a per CPU local lock to serialize bottomhalfs. As local_bh_disable() can nest the lock can only be acquired on the outermost invocation of local_bh_disable() and released when the nest count becomes zero. Tasks which hold the local lock can be preempted so its required to keep track of the nest count per task. Add a RT only counter to task struct and adjust the relevant macros in preempt.h. Signed-off-by: Thomas Gleixner Tested-by: Sebastian Andrzej Siewior Reviewed-by: Frederic Weisbecker Signed-off-by: Sebastian Andrzej Siewior --- include/linux/hardirq.h | 1 + include/linux/preempt.h | 6 +++++- include/linux/sched.h | 3 +++ 3 files changed, 9 insertions(+), 1 deletion(-) diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 0926e9ca4d85..76878b357ffa 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -6,6 +6,7 @@ #include #include #include +#include #include #include diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 69cc8b64aa3a..9881eac0698f 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -79,7 +79,11 @@ #define nmi_count() (preempt_count() & NMI_MASK) #define hardirq_count() (preempt_count() & HARDIRQ_MASK) -#define softirq_count() (preempt_count() & SOFTIRQ_MASK) +#ifdef CONFIG_PREEMPT_RT +# define softirq_count() (current->softirq_disable_cnt & SOFTIRQ_MASK) +#else +# define softirq_count() (preempt_count() & SOFTIRQ_MASK) +#endif #define irq_count() (nmi_count() | hardirq_count() | softirq_count()) /* diff --git a/include/linux/sched.h b/include/linux/sched.h index e66777296857..d8f0c94a9921 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1149,6 +1149,9 @@ struct task_struct { int softirq_context; int irq_config; #endif +#ifdef CONFIG_PREEMPT_RT + int softirq_disable_cnt; +#endif #ifdef CONFIG_LOCKDEP # define MAX_LOCK_DEPTH 48UL -- Gitee From d8f021627ad9d1c224408ed59eb7e7c2d42e541d Mon Sep 17 00:00:00 2001 From: zr_yy Date: Mon, 5 Jun 2023 11:59:15 +0800 Subject: [PATCH 2/2] irqtime: Make accounting correct on RT commit be5609dd3a7a998d8bdf7db391b31a915fdb27aa upstream. vtime_account_irq and irqtime_account_irq() base checks on preempt_count() which fails on RT because preempt_count() does not contain the softirq accounting which is seperate on RT. These checks do not need the full preempt count as they only operate on the hard and softirq sections. Use irq_count() instead which provides the correct value on both RT and non RT kernels. The compiler is clever enough to fold the masking for !RT: 99b: 65 8b 05 00 00 00 00 mov %gs:0x0(%rip),%eax - 9a2: 25 ff ff ff 7f and $0x7fffffff,%eax + 9a2: 25 00 ff ff 00 and $0xffff00,%eax Reported-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Tested-by: Sebastian Andrzej Siewior Reviewed-by: Frederic Weisbecker Signed-off-by: Sebastian Andrzej Siewior --- kernel/sched/cputime.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 95a9c5603d29..a22e459531c7 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -60,7 +60,7 @@ void irqtime_account_irq(struct task_struct *curr, unsigned int offset) cpu = smp_processor_id(); delta = sched_clock_cpu(cpu) - irqtime->irq_start_time; irqtime->irq_start_time += delta; - pc = preempt_count() - offset; + pc = irq_count() - offset; /* * We do not account for softirq time from ksoftirqd here. @@ -419,7 +419,7 @@ void vtime_task_switch(struct task_struct *prev) void vtime_account_irq(struct task_struct *tsk, unsigned int offset) { - unsigned int pc = preempt_count() - offset; + unsigned int pc = irq_count() - offset; if (pc & HARDIRQ_OFFSET) { vtime_account_hardirq(tsk); -- Gitee