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Subject[tip: x86/entry] genirq: Provide irq_enter/exit_rcu()
The following commit has been merged into the x86/entry branch of tip:

Commit-ID: a59262f6413b82992626754b46383a615bfac152
Gitweb: https://git.kernel.org/tip/a59262f6413b82992626754b46383a615bfac152
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Thu, 21 May 2020 22:05:21 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 26 May 2020 19:06:27 +02:00

genirq: Provide irq_enter/exit_rcu()

irq_enter()/exit() currently include RCU handling. To properly separate the RCU
handling code, provide variants which contain only the non-RCU related
functionality.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202117.567023613@linutronix.de
---
include/linux/hardirq.h | 13 +++++++++++--
kernel/softirq.c | 35 +++++++++++++++++++++++++++--------
2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 29b862a..3dc9102 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -40,7 +40,11 @@ static __always_inline void rcu_irq_enter_check_tick(void)
/*
* Enter irq context (on NO_HZ, update jiffies):
*/
-extern void irq_enter(void);
+void irq_enter(void);
+/*
+ * Like irq_enter(), but RCU is already watching.
+ */
+void irq_enter_rcu(void);

/*
* Exit irq context without processing softirqs:
@@ -55,7 +59,12 @@ extern void irq_enter(void);
/*
* Exit irq context and process softirqs if needed:
*/
-extern void irq_exit(void);
+void irq_exit(void);
+
+/*
+ * Like irq_exit(), but return with RCU watching.
+ */
+void irq_exit_rcu(void);

#ifndef arch_nmi_enter
#define arch_nmi_enter() do { } while (0)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index a47c6dd..beb8e3a 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -339,12 +339,11 @@ asmlinkage __visible void do_softirq(void)
local_irq_restore(flags);
}

-/*
- * Enter an interrupt context.
+/**
+ * irq_enter_rcu - Enter an interrupt context with RCU watching
*/
-void irq_enter(void)
+void irq_enter_rcu(void)
{
- rcu_irq_enter();
if (is_idle_task(current) && !in_interrupt()) {
/*
* Prevent raise_softirq from needlessly waking up ksoftirqd
@@ -354,10 +353,18 @@ void irq_enter(void)
tick_irq_enter();
_local_bh_enable();
}
-
__irq_enter();
}

+/**
+ * irq_enter - Enter an interrupt context including RCU update
+ */
+void irq_enter(void)
+{
+ rcu_irq_enter();
+ irq_enter_rcu();
+}
+
static inline void invoke_softirq(void)
{
if (ksoftirqd_running(local_softirq_pending()))
@@ -397,10 +404,12 @@ static inline void tick_irq_exit(void)
#endif
}

-/*
- * Exit an interrupt context. Process softirqs if needed and possible:
+/**
+ * irq_exit_rcu() - Exit an interrupt context without updating RCU
+ *
+ * Also processes softirqs if needed and possible.
*/
-void irq_exit(void)
+void irq_exit_rcu(void)
{
#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
local_irq_disable();
@@ -413,6 +422,16 @@ void irq_exit(void)
invoke_softirq();

tick_irq_exit();
+}
+
+/**
+ * irq_exit - Exit an interrupt context, update RCU and lockdep
+ *
+ * Also processes softirqs if needed and possible.
+ */
+void irq_exit(void)
+{
+ irq_exit_rcu();
rcu_irq_exit();
/* must be last! */
lockdep_hardirq_exit();
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