perf_events: Fix races and clean up perf_event and perf_mmap_data interaction

In order to move toward separate buffer objects, rework the whole
perf_mmap_data construct to be a more self-sufficient entity, one
with its own lifetime rules.

This greatly sanitizes the whole output redirection code, which
was riddled with bugs and races.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index fb6c91eac7e3..490698590d6e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -585,6 +585,7 @@ enum perf_event_active_state {
 struct file;
 
 struct perf_mmap_data {
+        atomic_t                        refcount;
         struct rcu_head                 rcu_head;
 #ifdef CONFIG_PERF_USE_VMALLOC
         struct work_struct              work;
@@ -592,7 +593,6 @@ struct perf_mmap_data {
 #endif
         int                             nr_pages;       /* nr of data pages  */
         int                             writable;       /* are we writable   */
-        int                             nr_locked;      /* nr pages mlocked  */
 
         atomic_t                        poll;           /* POLL_ for wakeups */
 
@@ -643,7 +643,6 @@ struct perf_event {
         int                             nr_siblings;
         int                             group_flags;
         struct perf_event               *group_leader;
-        struct perf_event               *output;
         const struct pmu                *pmu;
 
         enum perf_event_active_state    state;
@@ -704,6 +703,8 @@ struct perf_event {
         /* mmap bits */
         struct mutex                    mmap_mutex;
         atomic_t                        mmap_count;
+        int                             mmap_locked;
+        struct user_struct              *mmap_user;
         struct perf_mmap_data           *data;
 
         /* poll related */