On 11/22/2013 08:46 AM, Peter Zijlstra wrote:
How about the below version?
---
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -61,19 +61,20 @@ static void perf_output_put_handle(struc
*
* kernel user
*
- * READ ->data_tail READ ->data_head
- * smp_mb() (A) smp_rmb() (C)
- * WRITE $data READ $data
- * smp_wmb() (B) smp_mb() (D)
- * STORE ->data_head WRITE ->data_tail
+ * if (LOAD ->data_tail) { LOAD ->data_head
+ * (A) smp_rmb() (C)
+ * STORE $data LOAD $data
+ * smp_wmb() (B) smp_mb() (D)
+ * STORE ->data_head STORE ->data_tail
I wasn't subscribed to linux-arch so missed the smp_store_release()
outcome, if there was one.
Are (B) and (D) still slated for changing to STORE.rel semantics,
aka smp_store_release()?
I realize that, for the perf ring buffer, (D) is in userspace but
I'm also interested in non-perf situations where (D) would be in the
kernel.
Regards,
Peter Hurley
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