From: Michal Schmidt Date: Wed, 6 Feb 2008 09:37:07 +0000 (-0800) Subject: proc: loadavg reading race X-Git-Tag: upstream/snapshot3+hdmi~27904 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=07a154b2bb9b528a39ddc777399482c1fa27fdb8;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git 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 --- 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),