The patch titled
add rcu_assign_index() if ever needed
has been removed from the -mm tree. Its filename was
add-rcu_assign_index-if-ever-needed.patch
This patch was dropped because it isn't needed :)
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: add rcu_assign_index() if ever needed
From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
This is a speculative patch that as far as I can tell is not yet required.
If anyone applies RCU to a data structure allocated out of an array, using
array indexes in place of pointers to link the array elements together,
then the rcu_assign_index() function in this patch will be needed to assign
a given element's array index to the RCU-traversed index. The
implementation is exactly that of the old rcu_assign_pointer(), so is
extremely well tested.
The existing rcu_assign_pointer() will emit a compiler warning in cases
where rcu_assign_index() is required.
[akpm@xxxxxxxxxxxxxxxxxxxx: fix comment typo]
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Gautham R Shenoy <ego@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rcupdate.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff -puN include/linux/rcupdate.h~add-rcu_assign_index-if-ever-needed include/linux/rcupdate.h
--- a/include/linux/rcupdate.h~add-rcu_assign_index-if-ever-needed
+++ a/include/linux/rcupdate.h
@@ -203,6 +203,24 @@ void name(void) \
}
/**
+ * rcu_assign_index - assign (publicize) a index of a newly
+ * initialized array element that will be dereferenced by RCU
+ * read-side critical sections. Returns the value assigned.
+ *
+ * Inserts memory barriers on architectures that require them
+ * (pretty much all of them other than x86), and also prevents
+ * the compiler from reordering the code that initializes the
+ * structure after the index assignment. More importantly, this
+ * call documents which indexes will be dereferenced by RCU read-side
+ * code.
+ */
+
+#define rcu_assign_index(p, v) ({ \
+ smp_wmb(); \
+ (p) = (v); \
+ })
+
+/**
* synchronize_sched - block until all CPUs have exited any non-preemptive
* kernel code sequences.
*
_
Patches currently in -mm which might be from paulmck@xxxxxxxxxxxxxxxxxx are
origin.patch
linux-next.patch
add-rcu_assign_index-if-ever-needed.patch
add-warn_on_secs-macro.patch
use-warn_on_secs-in-rcupreempth.patch
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