From a4b2fa58f0b8dabae3f30be80fe317da32c5b121 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 9 Mar 2021 09:55:54 +0100 Subject: [PATCH 147/323] irqtime: Make accounting correct on RT Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz 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 02a7932c7383..02a5aa60fe7e 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. @@ -421,7 +421,7 @@ 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); -- 2.43.0