[PATCH 3/3] sched: Add cond_resched_rwlock

[Ben Gardon <bgardon@google.com>]

Rescheduling while holding a spin lock is essential for keeping long
running kernel operations running smoothly. Add the facility to
cond_resched rwlocks.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
 include/linux/sched.h | 12 ++++++++++++
 kernel/sched/core.c   | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 77179160ec3ab..2eb0c53fce115 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1841,12 +1841,24 @@ static inline int _cond_resched(void) { return 0; }
 })
 
 extern int __cond_resched_lock(spinlock_t *lock);
+extern int __cond_resched_rwlock_read(rwlock_t *lock);
+extern int __cond_resched_rwlock_write(rwlock_t *lock);
 
 #define cond_resched_lock(lock) ({				\
 	___might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);\
 	__cond_resched_lock(lock);				\
 })
 
+#define cond_resched_rwlock_read(lock) ({			\
+	__might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);	\
+	__cond_resched_rwlock_read(lock);			\
+})
+
+#define cond_resched_rwlock_write(lock) ({			\
+	__might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);	\
+	__cond_resched_rwlock_write(lock);			\
+})
+
 static inline void cond_resched_rcu(void)
 {
 #if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_PREEMPT_RCU)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7d5ab55..ac58e7829a063 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6152,6 +6152,46 @@ int __cond_resched_lock(spinlock_t *lock)
 }
 EXPORT_SYMBOL(__cond_resched_lock);
 
+int __cond_resched_rwlock_read(rwlock_t *lock)
+{
+	int resched = should_resched(PREEMPT_LOCK_OFFSET);
+	int ret = 0;
+
+	lockdep_assert_held(lock);
+
+	if (rwlock_needbreak(lock) || resched) {
+		read_unlock(lock);
+		if (resched)
+			preempt_schedule_common();
+		else
+			cpu_relax();
+		ret = 1;
+		read_lock(lock);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(__cond_resched_rwlock_read);
+
+int __cond_resched_rwlock_write(rwlock_t *lock)
+{
+	int resched = should_resched(PREEMPT_LOCK_OFFSET);
+	int ret = 0;
+
+	lockdep_assert_held(lock);
+
+	if (rwlock_needbreak(lock) || resched) {
+		write_unlock(lock);
+		if (resched)
+			preempt_schedule_common();
+		else
+			cpu_relax();
+		ret = 1;
+		write_lock(lock);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(__cond_resched_rwlock_write);
+
 /**
  * yield - yield the current processor to other threads.
  *
-- 
2.29.0.rc2.309.g374f81d7ae-goog