locking/rwlock: Provide RT variant
Similar to rw_semaphores, on RT the rwlock substitution is not writer fair,
because it's not feasible to have a writer inherit its priority to
multiple readers. Readers blocked on a writer follow the normal rules of
priority inheritance. Like RT spinlocks, RT rwlocks are state preserving
across the slow lock operations (contended case).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.882793524@linutronix.de
diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c
index c8d7ad9..c5830cf 100644
--- a/kernel/locking/spinlock.c
+++ b/kernel/locking/spinlock.c
@@ -124,8 +124,11 @@ void __lockfunc __raw_##op##_lock_bh(locktype##_t *lock) \
* __[spin|read|write]_lock_bh()
*/
BUILD_LOCK_OPS(spin, raw_spinlock);
+
+#ifndef CONFIG_PREEMPT_RT
BUILD_LOCK_OPS(read, rwlock);
BUILD_LOCK_OPS(write, rwlock);
+#endif
#endif
@@ -209,6 +212,8 @@ void __lockfunc _raw_spin_unlock_bh(raw_spinlock_t *lock)
EXPORT_SYMBOL(_raw_spin_unlock_bh);
#endif
+#ifndef CONFIG_PREEMPT_RT
+
#ifndef CONFIG_INLINE_READ_TRYLOCK
int __lockfunc _raw_read_trylock(rwlock_t *lock)
{
@@ -353,6 +358,8 @@ void __lockfunc _raw_write_unlock_bh(rwlock_t *lock)
EXPORT_SYMBOL(_raw_write_unlock_bh);
#endif
+#endif /* !CONFIG_PREEMPT_RT */
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __lockfunc _raw_spin_lock_nested(raw_spinlock_t *lock, int subclass)