srcu: Remove SRCU-lite implementation

This commit removes the SRCU-lite implementation, which has been replaced
by SRCU-fast.

Both SRCU-lite and SRCU-fast provide faster readers by dropping the
smp_mb() call from their lock and unlock primitives, but incur a pair
of added RCU grace periods during the SRCU grace period.  There is a
trivial mapping from the SRCU-lite API to that of SRCU-fast, so there
should be no transition issues.

[ paulmck: Apply Christoph Hellwig feedback. ]

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>

1 files changed, 0 insertions, 38 deletions

diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 8bed7e6cc4c1..bf44d8d1e69e 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -278,44 +278,6 @@ static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_fast().");
 }
 
-/*
- * Counts the new reader in the appropriate per-CPU element of the
- * srcu_struct.  Returns an index that must be passed to the matching
- * srcu_read_unlock_lite().
- *
- * Note that this_cpu_inc() is an RCU read-side critical section either
- * because it disables interrupts, because it is a single instruction,
- * or because it is a read-modify-write atomic operation, depending on
- * the whims of the architecture.
- */
-static inline int __srcu_read_lock_lite(struct srcu_struct *ssp)
-{
-	struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp);
-
-	RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite().");
-	this_cpu_inc(scp->srcu_locks.counter); /* Y */
-	barrier(); /* Avoid leaking the critical section. */
-	return __srcu_ptr_to_ctr(ssp, scp);
-}
-
-/*
- * Removes the count for the old reader from the appropriate
- * per-CPU element of the srcu_struct.  Note that this may well be a
- * different CPU than that which was incremented by the corresponding
- * srcu_read_lock_lite(), but it must be within the same task.
- *
- * Note that this_cpu_inc() is an RCU read-side critical section either
- * because it disables interrupts, because it is a single instruction,
- * or because it is a read-modify-write atomic operation, depending on
- * the whims of the architecture.
- */
-static inline void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx)
-{
-	barrier();  /* Avoid leaking the critical section. */
-	this_cpu_inc(__srcu_ctr_to_ptr(ssp, idx)->srcu_unlocks.counter);  /* Z */
-	RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_lite().");
-}
-
 void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor);
 
 // Record reader usage even for CONFIG_PROVE_RCU=n kernels.  This is