Messages in this thread Patch in this message | | | Date | Sat, 23 Oct 2004 13:27:23 -0700 | From | "Paul E. McKenney" <> | Subject | [PATCH 1/3] RCU: rcu_assign_pointer() removal of memory barriers |
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This patch adds the rcu_assign_pointer() API that helps reduce the need for explicit memory barriers in code that uses RCU. This API buries the required memory barriers in a macro that also does the assignment. This has been tested successfully on i386 and ppc64.
Signed-off-by: <paulmck@us.ibm.com>
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rcupdate.h | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+)
diff -urpN -X ../dontdiff linux-2.5/include/linux/rcupdate.h linux-2.5-rap/include/linux/rcupdate.h --- linux-2.5/include/linux/rcupdate.h Tue Sep 7 10:04:29 2004 +++ linux-2.5-rap/include/linux/rcupdate.h Tue Sep 7 12:12:09 2004 @@ -238,6 +238,24 @@ static inline int rcu_pending(int cpu) (_________p1); \ }) +/** + * rcu_assign_pointer - assign (publicize) a pointer to a newly + * initialized structure 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 pointer assignment. More importantly, this + * call documents which pointers will be dereferenced by RCU read-side + * code. + */ + +#define rcu_assign_pointer(p, v) ({ \ + smp_wmb(); \ + (p) = (v); \ + }) + extern void rcu_init(void); extern void rcu_check_callbacks(int cpu, int user); extern void rcu_restart_cpu(int cpu); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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