[tip:perfcounters/core] perf_counter: Change data head from u32 to u64

tip-bot for Peter Zijlstra
2009-06-02T20:17:53Z

Commit-ID: 8e3747c13c39246c7e46def7cf495d9d21d4c5f9
Gitweb: http://git.kernel.org/tip/8e3747c13c39246c7e46def7cf495d9d21d4c5f9
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 2 Jun 2009 16:16:02 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 2 Jun 2009 21:45:32 +0200

perf_counter: Change data head from u32 to u64

Since some people worried that 4G might not be a large enough
as an mmap data window, extend it to 64 bit for capable
platforms.

Reported-by: Stephane Eranian <eranian@googlemail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
include/linux/perf_counter.h | 7 ++++---
kernel/perf_counter.c | 15 ++++++++-------
2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index cef9931..c046f7d 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -212,7 +212,7 @@ struct perf_counter_mmap_page {
* User-space reading this value should issue an rmb(), on SMP capable
* platforms, after reading this value -- see perf_counter_wakeup().
*/
- __u32 data_head; /* head in the data section */
+ __u64 data_head; /* head in the data section */
};

#define PERF_EVENT_MISC_CPUMODE_MASK (3 << 0)
@@ -397,10 +397,11 @@ struct perf_mmap_data {
int nr_locked; /* nr pages mlocked */

atomic_t poll; /* POLL_ for wakeups */
- atomic_t head; /* write position */
atomic_t events; /* event limit */

- atomic_t done_head; /* completed head */
+ atomic_long_t head; /* write position */
+ atomic_long_t done_head; /* completed head */
+
atomic_t lock; /* concurrent writes */

atomic_t wakeup; /* needs a wakeup */
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 5ecd998..3f11a2b 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -2067,8 +2067,8 @@ __weak struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
struct perf_output_handle {
struct perf_counter *counter;
struct perf_mmap_data *data;
- unsigned int offset;
- unsigned int head;
+ unsigned long head;
+ unsigned long offset;
int nmi;
int overflow;
int locked;
@@ -2122,7 +2122,8 @@ static void perf_output_lock(struct perf_output_handle *handle)
static void perf_output_unlock(struct perf_output_handle *handle)
{
struct perf_mmap_data *data = handle->data;
- int head, cpu;
+ unsigned long head;
+ int cpu;

data->done_head = data->head;

@@ -2135,7 +2136,7 @@ again:
* before we publish the new head, matched by a rmb() in userspace when
* reading this position.
*/
- while ((head = atomic_xchg(&data->done_head, 0)))
+ while ((head = atomic_long_xchg(&data->done_head, 0)))
data->user_page->data_head = head;

/*
@@ -2148,7 +2149,7 @@ again:
/*
* Therefore we have to validate we did not indeed do so.
*/
- if (unlikely(atomic_read(&data->done_head))) {
+ if (unlikely(atomic_long_read(&data->done_head))) {
/*
* Since we had it locked, we can lock it again.
*/
@@ -2195,7 +2196,7 @@ static int perf_output_begin(struct perf_output_handle *handle,
do {
offset = head = atomic_read(&data->head);
head += size;
- } while (atomic_cmpxchg(&data->head, offset, head) != offset);
+ } while (atomic_long_cmpxchg(&data->head, offset, head) != offset);

handle->offset = offset;
handle->head = head;
@@ -2246,7 +2247,7 @@ static void perf_output_copy(struct perf_output_handle *handle,
* Check we didn't copy past our reservation window, taking the
* possible unsigned int wrap into account.
*/
- WARN_ON_ONCE(((int)(handle->head - handle->offset)) < 0);
+ WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0);
}

#define perf_output_put(handle, x) \