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Commit 07a154b2 authored by Michal Schmidt's avatar Michal Schmidt Committed by Linus Torvalds
Browse files

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: default avatarMichal Schmidt <mschmidt@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0a76fe8e

fs/proc/proc_misc.c

+8 −3
Original line number Diff line number Diff line
@@ -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));



	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),