[patch 12/19] softirq: Add RT specific softirq accounting

Thomas Gleixner
2020-11-13T14:25:14Z

RT requires the softirq to be preemptible and uses a per CPU local lock to
protect BH disabled sections and softirq processing. Therefore RT cannot
use the preempt counter to keep track of BH disabled/serving.

Add a RT only counter to task struct and adjust the relevant macros in
preempt.h.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/hardirq.h | 1 +
include/linux/preempt.h | 6 +++++-
include/linux/sched.h | 3 +++
3 files changed, 9 insertions(+), 1 deletion(-)

--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -6,6 +6,7 @@
#include <linux/preempt.h>
#include <linux/lockdep.h>
#include <linux/ftrace_irq.h>
+#include <linux/sched.h>
#include <linux/vtime.h>
#include <asm/hardirq.h>

--- 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())

/*
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1004,6 +1004,9 @@ 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