From 07a154b2bb9b528a39ddc777399482c1fa27fdb8 Mon Sep 17 00:00:00 2001 From: Michal Schmidt Date: Wed, 6 Feb 2008 01:37:07 -0800 Subject: 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 Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/proc_misc.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'fs') diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c index 383ff06..2686592 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), -- cgit v1.1