softirq: Eliminate unused cond_resched_softirq() macro

The cond_resched_softirq() macro is not used anywhere in mainline, so
this commit simplifies the kernel by eliminating it.

Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>

include/linux/sched.h

@@ -1613,7 +1613,6 @@ static inline int test_tsk_need_resched(struct task_struct *tsk)
  * explicit rescheduling in places that are safe. The return
  * value indicates whether a reschedule was done in fact.
  * cond_resched_lock() will drop the spinlock before scheduling,
- * cond_resched_softirq() will enable bhs before scheduling.
  */
 #ifndef CONFIG_PREEMPT
 extern int _cond_resched(void);
@@ -1633,13 +1632,6 @@ extern int __cond_resched_lock(spinlock_t *lock);
 	__cond_resched_lock(lock);				\
 })
 
-extern int __cond_resched_softirq(void);
-
-#define cond_resched_softirq() ({					\
-	___might_sleep(__FILE__, __LINE__, SOFTIRQ_DISABLE_OFFSET);	\
-	__cond_resched_softirq();					\
-})
-
 static inline void cond_resched_rcu(void)
 {
 #if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_PREEMPT_RCU)

kernel/sched/core.c

@@ -5012,20 +5012,6 @@ int __cond_resched_lock(spinlock_t *lock)
 }
 EXPORT_SYMBOL(__cond_resched_lock);
 
-int __sched __cond_resched_softirq(void)
-{
-	BUG_ON(!in_softirq());
-
-	if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
-		local_bh_enable();
-		preempt_schedule_common();
-		local_bh_disable();
-		return 1;
-	}
-	return 0;
-}
-EXPORT_SYMBOL(__cond_resched_softirq);
-
 /**
  * yield - yield the current processor to other threads.
  *

kernel/softirq.c

@@ -145,8 +145,7 @@ static void __local_bh_enable(unsigned int cnt)
 }
 
 /*
- * Special-case - softirqs can safely be enabled in
- * cond_resched_softirq(), or by __do_softirq(),
+ * Special-case - softirqs can safely be enabled by __do_softirq(),
  * without processing still-pending softirqs:
  */
 void _local_bh_enable(void)