linux-kernel - [PATCH] perf:util:dso: Using O_CLOEXEC in do

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Message-ID: <20180115050448.GA20759@udknight>
Date:   Mon, 15 Jan 2018 13:04:48 +0800
From:   Wang YanQing <udknight@...il.com>
To:     acme@...hat.com
Cc:     peterz@...radead.org, mingo@...hat.com, jolsa@...hat.com,
        alexander.shishkin@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: [PATCH] perf:util:dso: Using O_CLOEXEC in do_open

I meet strange behavior with below commands on my gentoo box:
1:perf kmem record
2:CTRL-C to stop 1
3:perf report
4:"Enter", "Enter", "Run scripts for all samples",
  "event_analyzing_sample".

Then perf report:
"
No kallsyms or vmlinux with build-id xxxx was found
/lib/modules/4.10.0+/build/vmlinux with build id xxxx not found,
continuing without symbols
".

It is strange because I am sure /lib/modules/4.10.0+/build/vmlinux
is right for perf.data.

After digging, I find out the reason is "perf report" generates many
open fds, then "script_browse" uses popen to run "perf script" which
run out of open files. The gentoo box has a small default value for
"max open files", 1024. Yes, "ulimit -n " with a bigger number could
fix it, but I think that using O_CLOEXEC in do_open is a better way.

Signed-off-by: Wang YanQing <udknight@...il.com>
---
 tools/perf/util/dso.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index d5b6f7f..36ef45b 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -446,7 +446,7 @@ static int do_open(char *name)
 	char sbuf[STRERR_BUFSIZE];

 	do {
-		fd = open(name, O_RDONLY);
+		fd = open(name, O_RDONLY|O_CLOEXEC);
 		if (fd >= 0)
 			return fd;

-- 
1.8.5.6.2.g3d8a54e.dirty