[PATCH 03/24] sched: Add cond_resched_rwlock

Ben Gardon
2021-01-12T18:12:18Z

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

CC: Ingo Molnar <mingo@redhat.com>
CC: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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 5d1378e5a040..3052d16da3cf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1883,12 +1883,24 @@ 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 15d2562118d1..ade357642279 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6695,6 +6695,46 @@ 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_read(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_write(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.
*
--
2.30.0.284.gd98b1dd5eaa7-goog