tools/memory-model: Finish the removal of rb-dep, smp_read_barrier_de…

…pends(), and lockless_dereference()

Commit:

  bf28ae5 ("tools/memory-model: Remove rb-dep, smp_read_barrier_depends, and lockless_dereference")

was merged too early, while it was still in RFC form.  This patch adds in
the missing pieces.

Akira pointed out some typos in the original patch, and he noted that
cheatsheet.txt should indicate that READ_ONCE() now implies an address
dependency.  Andrea suggested documenting the relationship betwwen
unsuccessful RMW operations and address dependencies.

Andrea pointed out that the macro for rcu_dereference() in linux.def
should now use the "once" annotation instead of "deref".  He also
suggested that the comments should mention commit:

  5a8897c ("locking/atomics/alpha: Add smp_read_barrier_depends() to _release()/_relaxed() atomics")

... as an important precursor, and he contributed commit:

  cb13b42 ("locking/xchg/alpha: Add unconditional memory barrier to cmpxchg()")

which is another prerequisite.

Suggested-by: Akira Yokosawa <[email protected]>
Suggested-by: Andrea Parri <[email protected]>
Signed-off-by: Alan Stern <[email protected]>
[ Fixed read_read_lock() typo reported by Akira. ]
Signed-off-by: Paul E. McKenney <[email protected]>
Acked-by: Andrea Parri <[email protected]>
Acked-by: Akira Yokosawa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Fixes: bf28ae5 ("tools/memory-model: Remove rb-dep, smp_read_barrier_depends, and lockless_dereference")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

tools/memory-model/Documentation/cheatsheet.txt

@@ -1,11 +1,11 @@
                                   Prior Operation     Subsequent Operation
                                   ---------------  ---------------------------
                                C  Self  R  W  RWM  Self  R  W  DR  DW  RMW  SV
-                              __  ----  -  -  ---  ----  -  -  --  --  ---  --
+                              --  ----  -  -  ---  ----  -  -  --  --  ---  --
 
 Store, e.g., WRITE_ONCE()            Y                                       Y
-Load, e.g., READ_ONCE()              Y                              Y        Y
-Unsuccessful RMW operation           Y                              Y        Y
+Load, e.g., READ_ONCE()              Y                          Y   Y        Y
+Unsuccessful RMW operation           Y                          Y   Y        Y
 rcu_dereference()                    Y                          Y   Y        Y
 Successful *_acquire()               R                   Y  Y   Y   Y    Y   Y
 Successful *_release()         C        Y  Y    Y     W                      Y

tools/memory-model/Documentation/explanation.txt

@@ -826,7 +826,7 @@ A-cumulative; they only affect the propagation of stores that are
 executed on C before the fence (i.e., those which precede the fence in
 program order).
 
-read_lock(), rcu_read_unlock(), and synchronize_rcu() fences have
+rcu_read_lock(), rcu_read_unlock(), and synchronize_rcu() fences have
 other properties which we discuss later.
 
 
@@ -1138,7 +1138,7 @@ final effect is that even though the two loads really are executed in
 program order, it appears that they aren't.
 
 This could not have happened if the local cache had processed the
-incoming stores in FIFO order.  In constrast, other architectures
+incoming stores in FIFO order.  By contrast, other architectures
 maintain at least the appearance of FIFO order.
 
 In practice, this difficulty is solved by inserting a special fence

tools/memory-model/linux-kernel.def

@@ -13,7 +13,7 @@ WRITE_ONCE(X,V) { __store{once}(X,V); }
 smp_store_release(X,V) { __store{release}(*X,V); }
 smp_load_acquire(X) __load{acquire}(*X)
 rcu_assign_pointer(X,V) { __store{release}(X,V); }
-rcu_dereference(X) __load{deref}(X)
+rcu_dereference(X) __load{once}(X)
 
 // Fences
 smp_mb() { __fence{mb} ; }