The patch titled
proc: loadavg reading race
has been added to the -mm tree. Its filename is
proc-loadavg-reading-race.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: proc: loadavg reading race
From: Michal Schmidt <mschmidt@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/proc_misc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff -puN fs/proc/proc_misc.c~proc-loadavg-reading-race fs/proc/proc_misc.c
--- a/fs/proc/proc_misc.c~proc-loadavg-reading-race
+++ a/fs/proc/proc_misc.c
@@ -84,10 +84,15 @@ static int loadavg_read_proc(char *page,
{
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),
_
Patches currently in -mm which might be from mschmidt@xxxxxxxxxx are
pci-use-pci=bfsort-for-hp-dl385-g2-dl585-g2.patch
proc-loadavg-reading-race.patch
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