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Date: Mon, 12 Nov 2007 14:23:44 +0100 From: Michal Schmidt <mschmidt@...hat.com> To: linux-kernel@...r.kernel.org Cc: Michal Schmidt <mschmidt@...hat.com> 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@...hat.com> --- fs/proc/proc_misc.c | 11 ++++++++--- 1 files changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c index e0d064e..10cc9ad 100644 --- a/fs/proc/proc_misc.c +++ b/fs/proc/proc_misc.c @@ -83,10 +83,15 @@ 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), -- 1.5.3.3 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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