[tip:perf/core] perf tools: Fine tune readn function

[tip-bot for Jiri Olsa]

Commit-ID:  838d14520267769648fb2fc2a637107a1d102590
Gitweb:     http://git.kernel.org/tip/838d14520267769648fb2fc2a637107a1d102590
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Thu, 28 Nov 2013 11:30:15 +0100
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 2 Dec 2013 09:22:46 -0300

perf tools: Fine tune readn function

Added a 'left' variable to make the flow clearer, and added a debug
check for the return value - returning 'n' is more obvious.

Added small comment for readn.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Original-patch-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1385634619-8129-4-git-send-email-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/util.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 9440481..6ea0b4a 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -6,6 +6,7 @@
 #endif
 #include <stdio.h>
 #include <stdlib.h>
+#include <linux/kernel.h>
 
 /*
  * XXX We need to find a better place for these things...
@@ -151,21 +152,26 @@ unsigned long convert_unit(unsigned long value, char *unit)
 	return value;
 }
 
+/*
+ * Read exactly 'n' bytes or return an error.
+ */
 ssize_t readn(int fd, void *buf, size_t n)
 {
 	void *buf_start = buf;
+	size_t left = n;
 
-	while (n) {
-		ssize_t ret = read(fd, buf, n);
+	while (left) {
+		ssize_t ret = read(fd, buf, left);
 
 		if (ret <= 0)
 			return ret;
 
-		n -= ret;
-		buf += ret;
+		left -= ret;
+		buf  += ret;
 	}
 
-	return buf - buf_start;
+	BUG_ON((size_t)(buf - buf_start) != n);
+	return n;
 }
 
 size_t hex_width(u64 v)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/