rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw().

These interfaces never did get used, so this commit removes them,
their rcutorture tests, and documentation referencing them.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

5 files changed, 7 insertions, 109 deletions

diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index 79e789b8b8ea..7703ec73a9bb 100644
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -354,12 +354,6 @@ over a rather long period of time, but improvements are always welcome!
         using RCU rather than SRCU, because RCU is almost always faster
         and easier to use than is SRCU.
 
-        If you need to enter your read-side critical section in a
-        hardirq or exception handler, and then exit that same read-side
-        critical section in the task that was interrupted, then you need
-        to srcu_read_lock_raw() and srcu_read_unlock_raw(), which avoid
-        the lockdep checking that would otherwise this practice illegal.
-
         Also unlike other forms of RCU, explicit initialization
         and cleanup is required via init_srcu_struct() and
         cleanup_srcu_struct().  These are passed a "struct srcu_struct"
diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index 7dce8a17eac2..d8a502387397 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -182,12 +182,6 @@ torture_type	The type of RCU to test, with string values as follows:
                 "srcu_expedited": srcu_read_lock(), srcu_read_unlock() and
                         synchronize_srcu_expedited().
 
-                "srcu_raw": srcu_read_lock_raw(), srcu_read_unlock_raw(),
-                        and call_srcu().
-
-                "srcu_raw_sync": srcu_read_lock_raw(), srcu_read_unlock_raw(),
-                        and synchronize_srcu().
-
                 "sched": preempt_disable(), preempt_enable(), and
                         call_rcu_sched().
 
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 10df0b82f459..0f0fb7c432c2 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -842,9 +842,7 @@ SRCU:	Critical sections	Grace period		Barrier
 
         srcu_read_lock          synchronize_srcu        srcu_barrier
         srcu_read_unlock        call_srcu
-        srcu_read_lock_raw      synchronize_srcu_expedited
-        srcu_read_unlock_raw
-        srcu_dereference
+        srcu_dereference        synchronize_srcu_expedited
 
 SRCU:   Initialization/cleanup
         init_srcu_struct
@@ -865,38 +863,32 @@ list can be helpful:
 
 a.      Will readers need to block?  If so, you need SRCU.
 
-b.      Is it necessary to start a read-side critical section in a
-        hardirq handler or exception handler, and then to complete
-        this read-side critical section in the task that was
-        interrupted?  If so, you need SRCU's srcu_read_lock_raw() and
-        srcu_read_unlock_raw() primitives.
-
-c.      What about the -rt patchset?  If readers would need to block
+b.      What about the -rt patchset?  If readers would need to block
         in an non-rt kernel, you need SRCU.  If readers would block
         in a -rt kernel, but not in a non-rt kernel, SRCU is not
         necessary.
 
-d.      Do you need to treat NMI handlers, hardirq handlers,
+c.      Do you need to treat NMI handlers, hardirq handlers,
         and code segments with preemption disabled (whether
         via preempt_disable(), local_irq_save(), local_bh_disable(),
         or some other mechanism) as if they were explicit RCU readers?
         If so, RCU-sched is the only choice that will work for you.
 
-e.      Do you need RCU grace periods to complete even in the face
+d.      Do you need RCU grace periods to complete even in the face
         of softirq monopolization of one or more of the CPUs?  For
         example, is your code subject to network-based denial-of-service
         attacks?  If so, you need RCU-bh.
 
-f.      Is your workload too update-intensive for normal use of
+e.      Is your workload too update-intensive for normal use of
         RCU, but inappropriate for other synchronization mechanisms?
         If so, consider SLAB_DESTROY_BY_RCU.  But please be careful!
 
-g.      Do you need read-side critical sections that are respected
+f.      Do you need read-side critical sections that are respected
         even though they are in the middle of the idle loop, during
         user-mode execution, or on an offlined CPU?  If so, SRCU is the
         only choice that will work for you.
 
-h.      Otherwise, use RCU.
+g.      Otherwise, use RCU.
 
 Of course, this all assumes that you have determined that RCU is in fact
 the right tool for your job.
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 04f4121a23ae..c114614ed172 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -237,47 +237,4 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
         __srcu_read_unlock(sp, idx);
 }
 
-/**
- * srcu_read_lock_raw - register a new reader for an SRCU-protected structure.
- * @sp: srcu_struct in which to register the new reader.
- *
- * Enter an SRCU read-side critical section.  Similar to srcu_read_lock(),
- * but avoids the RCU-lockdep checking.  This means that it is legal to
- * use srcu_read_lock_raw() in one context, for example, in an exception
- * handler, and then have the matching srcu_read_unlock_raw() in another
- * context, for example in the task that took the exception.
- *
- * However, the entire SRCU read-side critical section must reside within a
- * single task.  For example, beware of using srcu_read_lock_raw() in
- * a device interrupt handler and srcu_read_unlock() in the interrupted
- * task:  This will not work if interrupts are threaded.
- */
-static inline int srcu_read_lock_raw(struct srcu_struct *sp)
-{
-        unsigned long flags;
-        int ret;
-
-        local_irq_save(flags);
-        ret =  __srcu_read_lock(sp);
-        local_irq_restore(flags);
-        return ret;
-}
-
-/**
- * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure.
- * @sp: srcu_struct in which to unregister the old reader.
- * @idx: return value from corresponding srcu_read_lock_raw().
- *
- * Exit an SRCU read-side critical section without lockdep-RCU checking.
- * See srcu_read_lock_raw() for more details.
- */
-static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx)
-{
-        unsigned long flags;
-
-        local_irq_save(flags);
-        __srcu_read_unlock(sp, idx);
-        local_irq_restore(flags);
-}
-
 #endif
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index e1f3a8c96724..b1fa5510388d 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -695,44 +695,6 @@ static struct rcu_torture_ops srcu_sync_ops = {
         .name           = "srcu_sync"
 };
 
-static int srcu_torture_read_lock_raw(void) __acquires(&srcu_ctl)
-{
-        return srcu_read_lock_raw(&srcu_ctl);
-}
-
-static void srcu_torture_read_unlock_raw(int idx) __releases(&srcu_ctl)
-{
-        srcu_read_unlock_raw(&srcu_ctl, idx);
-}
-
-static struct rcu_torture_ops srcu_raw_ops = {
-        .init           = rcu_sync_torture_init,
-        .readlock       = srcu_torture_read_lock_raw,
-        .read_delay     = srcu_read_delay,
-        .readunlock     = srcu_torture_read_unlock_raw,
-        .completed      = srcu_torture_completed,
-        .deferred_free  = srcu_torture_deferred_free,
-        .sync           = srcu_torture_synchronize,
-        .call           = NULL,
-        .cb_barrier     = NULL,
-        .stats          = srcu_torture_stats,
-        .name           = "srcu_raw"
-};
-
-static struct rcu_torture_ops srcu_raw_sync_ops = {
-        .init           = rcu_sync_torture_init,
-        .readlock       = srcu_torture_read_lock_raw,
-        .read_delay     = srcu_read_delay,
-        .readunlock     = srcu_torture_read_unlock_raw,
-        .completed      = srcu_torture_completed,
-        .deferred_free  = rcu_sync_torture_deferred_free,
-        .sync           = srcu_torture_synchronize,
-        .call           = NULL,
-        .cb_barrier     = NULL,
-        .stats          = srcu_torture_stats,
-        .name           = "srcu_raw_sync"
-};
-
 static void srcu_torture_synchronize_expedited(void)
 {
         synchronize_srcu_expedited(&srcu_ctl);
@@ -1983,7 +1945,6 @@ rcu_torture_init(void)
                 { &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
                   &rcu_bh_ops, &rcu_bh_sync_ops, &rcu_bh_expedited_ops,
                   &srcu_ops, &srcu_sync_ops, &srcu_expedited_ops,
-                  &srcu_raw_ops, &srcu_raw_sync_ops,
                   &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
 
         mutex_lock(&fullstop_mutex);