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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-11-01 23:54:51 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-11-01 23:54:51 +0400 |
| commit | 9581b7d2689ad9a0a20ddaec0427b46ad774585b (patch) | |
| tree | f2eb9c9e4f2066c2ff1a7a3853ee6231ef879c11 /include | |
| parent | 9119e33e507d3b8fe234f2c2bafd3199ea2e883b (diff) | |
| parent | e8a923cc1fff6e627f906655ad52ee694ef2f6d7 (diff) | |
| download | linux-9581b7d2689ad9a0a20ddaec0427b46ad774585b.tar.xz | |
Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar:
"Two fixes:
- Fix 'NMI handler took too long to run' false positives
[ Genuine NMI overhead speedups will come for v3.13, this commit
only fixes a measurement bug ]
- Fix perf ring-buffer missed barrier causing (rare) ring-buffer data
corruption on ppc64"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86: Fix NMI measurements
perf: Fix perf ring buffer memory ordering
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/perf_event.h | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 009a655a5d35..2fc1602e23bb 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -456,13 +456,15 @@ struct perf_event_mmap_page { /* * Control data for the mmap() data buffer. * - * User-space reading the @data_head value should issue an rmb(), on - * SMP capable platforms, after reading this value -- see - * perf_event_wakeup(). + * User-space reading the @data_head value should issue an smp_rmb(), + * after reading this value. * * When the mapping is PROT_WRITE the @data_tail value should be - * written by userspace to reflect the last read data. In this case - * the kernel will not over-write unread data. + * written by userspace to reflect the last read data, after issueing + * an smp_mb() to separate the data read from the ->data_tail store. + * In this case the kernel will not over-write unread data. + * + * See perf_output_put_handle() for the data ordering. */ __u64 data_head; /* head in the data section */ __u64 data_tail; /* user-space written tail */ |