sched/preempt: Simplify irqentry_exit_cond_resched() callers

Currently callers of irqentry_exit_cond_resched() need to be aware of
whether the function should be indirected via a static call, leading to
ugly ifdeffery in callers.

Save them the hassle with a static inline wrapper that does the right
thing. The raw_irqentry_exit_cond_resched() will also be useful in
subsequent patches which will add conditional wrappers for preemption
functions.

Note: in arch/x86/entry/common.c, xen_pv_evtchn_do_upcall() always calls
irqentry_exit_cond_resched() directly, even when PREEMPT_DYNAMIC is in
use. I believe this is a latent bug (which this patch corrects), but I'm
not entirely certain this wasn't deliberate.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-4-mark.rutland@arm.com

include/linux/entry-common.h

@@ -454,11 +454,14 @@ irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
  *
  * Conditional reschedule with additional sanity checks.
  */
-void irqentry_exit_cond_resched(void);
+void raw_irqentry_exit_cond_resched(void);
 #ifdef CONFIG_PREEMPT_DYNAMIC
-#define irqentry_exit_cond_resched_dynamic_enabled	irqentry_exit_cond_resched
+#define irqentry_exit_cond_resched_dynamic_enabled	raw_irqentry_exit_cond_resched
 #define irqentry_exit_cond_resched_dynamic_disabled	NULL
-DECLARE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
+#define irqentry_exit_cond_resched()	static_call(irqentry_exit_cond_resched)()
+#else
+#define irqentry_exit_cond_resched()	raw_irqentry_exit_cond_resched()
 #endif
 
 /**

kernel/entry/common.c

@@ -380,7 +380,7 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 	return ret;
 }
 
-void irqentry_exit_cond_resched(void)
+void raw_irqentry_exit_cond_resched(void)
 {
 	if (!preempt_count()) {
 		/* Sanity check RCU and thread stack */
@@ -392,7 +392,7 @@ void irqentry_exit_cond_resched(void)
 	}
 }
 #ifdef CONFIG_PREEMPT_DYNAMIC
-DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
 #endif
 
 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
@@ -420,13 +420,9 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 		}
 
 		instrumentation_begin();
-		if (IS_ENABLED(CONFIG_PREEMPTION)) {
-#ifdef CONFIG_PREEMPT_DYNAMIC
-			static_call(irqentry_exit_cond_resched)();
-#else
+		if (IS_ENABLED(CONFIG_PREEMPTION))
 			irqentry_exit_cond_resched();
-#endif
-		}
+
 		/* Covers both tracing and lockdep */
 		trace_hardirqs_on();
 		instrumentation_end();