linux-kernel - [PATCH 10/10] perf symbols: Convert lseek + read to pread

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Date:	Thu, 29 Jan 2015 17:23:45 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Namhyung Kim <namhyung@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 10/10] perf symbols: Convert lseek + read to pread

From: Namhyung Kim <namhyung@...nel.org>

When dso_cache__read() is called, it reads data from the given offset
using lseek + normal read syscall.  It can be combined to a single pread
syscall.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: David Ahern <dsahern@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lkml.kernel.org/r/1422518843-25818-40-git-send-email-namhyung@kernel.org
[ Fixed it up when cherry picking it from the multi threaded patchkit ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/dso.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 45be944d450a..c2f7d3b90966 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -532,12 +532,8 @@ dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
 			break;
 
 		cache_offset = offset & DSO__DATA_CACHE_MASK;
-		ret = -EINVAL;
 
-		if (-1 == lseek(dso->data.fd, cache_offset, SEEK_SET))
-			break;
-
-		ret = read(dso->data.fd, cache->data, DSO__DATA_CACHE_SIZE);
+		ret = pread(dso->data.fd, cache->data, DSO__DATA_CACHE_SIZE, cache_offset);
 		if (ret <= 0)
 			break;
 
-- 
1.9.3

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