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

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 38b672d..d203c54 100644 (file)
--- 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..c4201b7 100644 (file)
--- 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();
@@ -425,13 +420,25 @@ 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.
  */
 void irq_exit(void)
 {
-       irq_exit_rcu();
+       __irq_exit_rcu();
        rcu_irq_exit();
         /* must be last! */
        lockdep_hardirq_exit();