perf evlist: Extract perf_mmap__read()

Extract event reader from perf_evlist__mmap_read() to perf__mmap_read().
Future commit will feed it with manually computed 'head' and 'old'
pointers.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1461723563-67451-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 85271e54a63b3370296740e6088459aee665cac6..96c71916e36744ae89785b273c4917f7b50b2645 100644 (file)
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -679,24 +679,15 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
        return NULL;
 }
 
-union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+static union perf_event *
+perf_mmap__read(struct perf_mmap *md, bool overwrite, u64 head,
+               u64 old, u64 *prev)
 {
-       struct perf_mmap *md = &evlist->mmap[idx];
-       u64 head;
-       u64 old = md->prev;
-       int diff;
        unsigned char *data = md->base + page_size;
        union perf_event *event = NULL;
+       int diff = head - old;
 
-       /*
-        * Check if event was unmapped due to a POLLHUP/POLLERR.
-        */
-       if (!atomic_read(&md->refcnt))
-               return NULL;
-
-       head = perf_mmap__read_head(md);
-       diff = head - old;
-       if (evlist->overwrite) {
+       if (overwrite) {
                /*
                 * If we're further behind than half the buffer, there's a chance
                 * the writer will bite our tail and mess up the samples under us.
@@ -751,11 +742,29 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
        }
 
 broken_event:
-       md->prev = old;
+       if (prev)
+               *prev = old;
 
        return event;
 }
 
+union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+{
+       struct perf_mmap *md = &evlist->mmap[idx];
+       u64 head;
+       u64 old = md->prev;
+
+       /*
+        * Check if event was unmapped due to a POLLHUP/POLLERR.
+        */
+       if (!atomic_read(&md->refcnt))
+               return NULL;
+
+       head = perf_mmap__read_head(md);
+
+       return perf_mmap__read(md, evlist->overwrite, head, old, &md->prev);
+}
+
 static bool perf_mmap__empty(struct perf_mmap *md)
 {
        return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;