From 07a154b2bb9b528a39ddc777399482c1fa27fdb8 Mon Sep 17 00:00:00 2001
From: Michal Schmidt <mschmidt@redhat.com>
Date: Wed, 6 Feb 2008 01:37:07 -0800
Subject: [PATCH] proc: loadavg reading race
The avenrun[] values are supposed to be protected by xtime_lock.
loadavg_read_proc does not use it. Theoretically this may result in an
occasional glitch when the value read from /proc/loadavg would be as much
as 1<<11 times higher than it should be.
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/proc/proc_misc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 383ff068ab2ec..2686592dbcb2b 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -84,10 +84,15 @@ static int loadavg_read_proc(char *page, char **start, off_t off,
{
int a, b, c;
int len;
+ unsigned long seq;
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ a = avenrun[0] + (FIXED_1/200);
+ b = avenrun[1] + (FIXED_1/200);
+ c = avenrun[2] + (FIXED_1/200);
+ } while (read_seqretry(&xtime_lock, seq));
- a = avenrun[0] + (FIXED_1/200);
- b = avenrun[1] + (FIXED_1/200);
- c = avenrun[2] + (FIXED_1/200);
len = sprintf(page,"%d.%02d %d.%02d %d.%02d %ld/%d %d\n",
LOAD_INT(a), LOAD_FRAC(a),
LOAD_INT(b), LOAD_FRAC(b),
--
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