[tip: x86/entry] x86/entry: Clarify irq_{enter,exit}_rcu()

tip-bot2 for Peter Zijlstra
2020-05-30T09:58:10Z

The following commit has been merged into the x86/entry branch of tip:

Commit-ID: b614345f52bcde8299a53132f5e48a9eb5a1f320
Gitweb: https://git.kernel.org/tip/b614345f52bcde8299a53132f5e48a9eb5a1f320
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 29 May 2020 23:27:39 +02:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 30 May 2020 10:00:10 +02:00

x86/entry: Clarify irq_{enter,exit}_rcu()

Because:

irq_enter_rcu() includes lockdep_hardirq_enter()
irq_exit_rcu() does *NOT* include lockdep_hardirq_exit()

Which resulted in two 'stray' lockdep_hardirq_exit() calls in
idtentry.h, and me spending a long time trying to find the matching
enter calls.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.359433429@infradead.org

---
arch/x86/include/asm/idtentry.h | 2 --
kernel/softirq.c | 19 +++++++++++++------
2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index d214a30..f8e2737 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -206,7 +206,6 @@ __visible noinstr void func(struct pt_regs *regs, \
kvm_set_cpu_l1tf_flush_l1d(); \
__##func (regs, (u8)error_code); \
irq_exit_rcu(); \
- lockdep_hardirq_exit(); \
instrumentation_end(); \
idtentry_exit_cond_rcu(regs, rcu_exit); \
} \
@@ -249,7 +248,6 @@ __visible noinstr void func(struct pt_regs *regs) \
kvm_set_cpu_l1tf_flush_l1d(); \
run_on_irqstack_cond(__##func, regs, regs); \
irq_exit_rcu(); \
- lockdep_hardirq_exit(); \
instrumentation_end(); \
idtentry_exit_cond_rcu(regs, rcu_exit); \
} \
diff --git a/kernel/softirq.c b/kernel/softirq.c
index beb8e3a..a3eb6eb 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -404,12 +404,7 @@ static inline void tick_irq_exit(void)
#endif
}

-/**
- * irq_exit_rcu() - Exit an interrupt context without updating RCU
- *
- * Also processes softirqs if needed and possible.
- */
-void irq_exit_rcu(void)
+static inline void __irq_exit_rcu(void)
{
#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
local_irq_disable();
@@ -425,6 +420,18 @@ void irq_exit_rcu(void)
}

/**
+ * irq_exit_rcu() - Exit an interrupt context without updating RCU
+ *
+ * Also processes softirqs if needed and possible.
+ */
+void irq_exit_rcu(void)
+{
+ __irq_exit_rcu();
+ /* must be last! */
+ lockdep_hardirq_exit();
+}
+
+/**
* irq_exit - Exit an interrupt context, update RCU and lockdep
*
* Also processes softirqs if needed and possible.