diff options
| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-05-05 17:50:22 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-05-05 20:18:30 +0200 |
| commit | c66de4a5be7913247bd83d79168f8e4420c9cfbc (patch) | |
| tree | c671172166d94be75ad9d6df1fdafa0c006c4609 | |
| parent | 066d7dea32c9bffe6decc0abe465627656cdd84e (diff) | |
perf_counter: uncouple data_head updates from wakeups
Keep data_head up-to-date irrespective of notifications. This fixes
the case where you disable a counter and don't get a notification for
the last few pending events, and it also allows polling usage.
[ Impact: increase precision of perfcounter mmap-ed fields ]
Suggested-by: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090505155436.925084300@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | include/linux/perf_counter.h | 4 | ||||
| -rw-r--r-- | kernel/perf_counter.c | 20 |
2 files changed, 12 insertions, 12 deletions
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index a356fa69796..17b63105f2a 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -362,9 +362,11 @@ struct perf_mmap_data { atomic_t head; /* write position */ atomic_t events; /* event limit */ - atomic_t wakeup_head; /* completed head */ + atomic_t done_head; /* completed head */ atomic_t lock; /* concurrent writes */ + atomic_t wakeup; /* needs a wakeup */ + struct perf_counter_mmap_page *user_page; void *data_pages[0]; }; diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 5f86a1156c9..ba5e921e1f3 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -1696,7 +1696,6 @@ struct perf_output_handle { struct perf_mmap_data *data; unsigned int offset; unsigned int head; - int wakeup; int nmi; int overflow; int locked; @@ -1752,8 +1751,7 @@ static void perf_output_unlock(struct perf_output_handle *handle) struct perf_mmap_data *data = handle->data; int head, cpu; - if (handle->wakeup) - data->wakeup_head = data->head; + data->done_head = data->head; if (!handle->locked) goto out; @@ -1764,13 +1762,11 @@ again: * before we publish the new head, matched by a rmb() in userspace when * reading this position. */ - while ((head = atomic_xchg(&data->wakeup_head, 0))) { + while ((head = atomic_xchg(&data->done_head, 0))) data->user_page->data_head = head; - handle->wakeup = 1; - } /* - * NMI can happen here, which means we can miss a wakeup_head update. + * NMI can happen here, which means we can miss a done_head update. */ cpu = atomic_xchg(&data->lock, 0); @@ -1779,7 +1775,7 @@ again: /* * Therefore we have to validate we did not indeed do so. */ - if (unlikely(atomic_read(&data->wakeup_head))) { + if (unlikely(atomic_read(&data->done_head))) { /* * Since we had it locked, we can lock it again. */ @@ -1789,7 +1785,7 @@ again: goto again; } - if (handle->wakeup) + if (atomic_xchg(&data->wakeup, 0)) perf_output_wakeup(handle); out: local_irq_restore(handle->flags); @@ -1824,7 +1820,9 @@ static int perf_output_begin(struct perf_output_handle *handle, handle->offset = offset; handle->head = head; - handle->wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT); + + if ((offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT)) + atomic_set(&data->wakeup, 1); return 0; @@ -1882,7 +1880,7 @@ static void perf_output_end(struct perf_output_handle *handle) int events = atomic_inc_return(&data->events); if (events >= wakeup_events) { atomic_sub(wakeup_events, &data->events); - handle->wakeup = 1; + atomic_set(&data->wakeup, 1); } } |