Conflicts: tools/perf/bench/numa.c
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| @@ -479,13 +479,15 @@ struct perf_event_mmap_page { · 478 unmodified lines | ||
| 479 | 479 | /* |
| 480 | 480 | * Control data for the mmap() data buffer. |
| 481 | 481 | * |
| 482 | − * User-space reading the @data_head value should issue an rmb(), on | |
| 483 | − * SMP capable platforms, after reading this value -- see | |
| 484 | − * perf_event_wakeup(). | |
| 482 | + * User-space reading the @data_head value should issue an smp_rmb(), | |
| 483 | + * after reading this value. | |
| 485 | 484 | * |
| 486 | 485 | * When the mapping is PROT_WRITE the @data_tail value should be |
| 487 | − * written by userspace to reflect the last read data. In this case | |
| 488 | − * the kernel will not over-write unread data. | |
| 486 | + * written by userspace to reflect the last read data, after issueing | |
| 487 | + * an smp_mb() to separate the data read from the ->data_tail store. | |
| 488 | + * In this case the kernel will not over-write unread data. | |
| 489 | + * | |
| 490 | + * See perf_output_put_handle() for the data ordering. | |
| 489 | 491 | */ |
| 490 | 492 | __u64 data_head; /* head in the data section */ |
| 491 | 493 | __u64 data_tail; /* user-space written tail */ |