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| author | Michal Schmidt <mschmidt@redhat.com> | 2008-02-06 01:37:07 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-06 10:41:04 -0800 |
| commit | 07a154b2bb9b528a39ddc777399482c1fa27fdb8 (patch) | |
| tree | 64355093ab4f470e67a301fb53e7d078ad4000f9 | |
| parent | 0a76fe8e50ee93a9d4a1badb1ec995852a6bcaf1 (diff) | |
| download | op-kernel-dev-07a154b2bb9b528a39ddc777399482c1fa27fdb8.zip op-kernel-dev-07a154b2bb9b528a39ddc777399482c1fa27fdb8.tar.gz | |
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@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | 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 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), |
