linux-kernel - [PATCH V4 08/15] perf mmap: discard legacy interface for mmap read

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Message-Id: <1516047651-164336-9-git-send-email-kan.liang@intel.com>
Date:   Mon, 15 Jan 2018 12:20:44 -0800
From:   kan.liang@...el.com
To:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     wangnan0@...wei.com, jolsa@...nel.org, namhyung@...nel.org,
        ak@...ux.intel.com, yao.jin@...ux.intel.com,
        Kan Liang <kan.liang@...el.com>
Subject: [PATCH V4 08/15] perf mmap: discard legacy interface for mmap read

From: Kan Liang <kan.liang@...el.com>

Discards perf_mmap__read_backward() and perf_mmap__read_catchup(). No
tools use them.

There are tools still use perf_mmap__read_forward(). Keep it, but add
comments to point to the new interface for future use.

Signed-off-by: Kan Liang <kan.liang@...el.com>
---
 tools/perf/util/mmap.c | 50 ++++----------------------------------------------
 tools/perf/util/mmap.h |  3 ---
 2 files changed, 4 insertions(+), 49 deletions(-)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index de50c71..c2a56bb 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -63,6 +63,10 @@ static union perf_event *perf_mmap__read(struct perf_mmap *map,
 	return event;
 }
 
+/*
+ * legacy interface for mmap read.
+ * Don't use it. Use perf_mmap__read_event().
+ */
 union perf_event *perf_mmap__read_forward(struct perf_mmap *map)
 {
 	u64 head;
@@ -78,41 +82,6 @@ union perf_event *perf_mmap__read_forward(struct perf_mmap *map)
 	return perf_mmap__read(map, &map->prev, head);
 }
 
-union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
-{
-	u64 head, end;
-
-	/*
-	 * Check if event was unmapped due to a POLLHUP/POLLERR.
-	 */
-	if (!refcount_read(&map->refcnt))
-		return NULL;
-
-	head = perf_mmap__read_head(map);
-	if (!head)
-		return NULL;
-
-	/*
-	 * 'head' pointer starts from 0. Kernel minus sizeof(record) form
-	 * it each time when kernel writes to it, so in fact 'head' is
-	 * negative. 'end' pointer is made manually by adding the size of
-	 * the ring buffer to 'head' pointer, means the validate data can
-	 * read is the whole ring buffer. If 'end' is positive, the ring
-	 * buffer has not fully filled, so we must adjust 'end' to 0.
-	 *
-	 * However, since both 'head' and 'end' is unsigned, we can't
-	 * simply compare 'end' against 0. Here we compare '-head' and
-	 * the size of the ring buffer, where -head is the number of bytes
-	 * kernel write to the ring buffer.
-	 */
-	if (-head < (u64)(map->mask + 1))
-		end = 0;
-	else
-		end = head + map->mask + 1;
-
-	return perf_mmap__read(map, &map->prev, end);
-}
-
 /*
  * Read event from ring buffer one by one.
  * Return one event for each call.
@@ -152,17 +121,6 @@ union perf_event *perf_mmap__read_event(struct perf_mmap *map,
 	return event;
 }
 
-void perf_mmap__read_catchup(struct perf_mmap *map)
-{
-	u64 head;
-
-	if (!refcount_read(&map->refcnt))
-		return;
-
-	head = perf_mmap__read_head(map);
-	map->prev = head;
-}
-
 static bool perf_mmap__empty(struct perf_mmap *map)
 {
 	return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base;
diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index 29d7c5d..303e5d2 100644
--- a/tools/perf/util/mmap.h
+++ b/tools/perf/util/mmap.h
@@ -65,8 +65,6 @@ void perf_mmap__put(struct perf_mmap *map);
 
 void perf_mmap__consume(struct perf_mmap *map, bool overwrite);
 
-void perf_mmap__read_catchup(struct perf_mmap *md);
-
 static inline u64 perf_mmap__read_head(struct perf_mmap *mm)
 {
 	struct perf_event_mmap_page *pc = mm->base;
@@ -87,7 +85,6 @@ static inline void perf_mmap__write_tail(struct perf_mmap *md, u64 tail)
 }
 
 union perf_event *perf_mmap__read_forward(struct perf_mmap *map);
-union perf_event *perf_mmap__read_backward(struct perf_mmap *map);
 
 union perf_event *perf_mmap__read_event(struct perf_mmap *map,
 					bool overwrite,
-- 
2.5.5