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>

1 files changed, 4 insertions, 3 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index cef9931793fd..c046f7d97cfa 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    */