cpu_cgroup_proc_loadavg() sums the per-CPU cfs_rq::nr_unint counters
into a plain int accumulator and prints it with %d:
int nr_running = 0;
...
nr_running += tg->cfs_rq[i]->nr_unint;
nr_unint is unsigned long and relies on signed reinterpretation to
fold the migration drift: a task can increment it on one CPU while
the matching decrement lands on another CPU after migration, so a
single per-CPU value can be far negative (stored as a huge unsigned
number) and only the sum over all CPUs is meaningful.
This is not a wrong-value fix: reading the drift as signed and adding
it folds to the same small non-negative sum whether the accumulator
is int or long. The change is for consistency and clarity, not
correctness:
- calc_load_fold_active() and calc_load_ve() fold the very same
per-CPU nr_unint in a long with an explicit (long) cast; this site
is the odd one out;
- an explicit (long) cast states the signed reinterpretation at the
read site instead of hiding it in an implicit unsigned-long-to-int
narrowing;
- a long accumulator prints correctly with %ld and could host a
"< 0" sanity check like calc_load_ve() has.
Accumulate in long, cast each term with (long), print with %ld.
Fixes: e4a432fe473c ("ve/proc/loadavg: Virtualize /proc/loadavg in Containers")
Reported-by: Pavel Tikhomirov <[email protected]>
https://virtuozzo.atlassian.net/browse/VSTOR-132310
Signed-off-by: Konstantin Khorenko <[email protected]>
---
kernel/sched/core.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d51d70ff7560..d5b4d8c97a0c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10045,7 +10045,7 @@ int cpu_cgroup_proc_loadavg(struct cgroup_subsys_state
*css,
struct cgroup *cgrp = css->cgroup;
struct task_group *tg = css_tg(css);
unsigned long avnrun[3];
- int nr_running = 0;
+ long nr_running = 0;
int i;
if (!test_bit(CGRP_VE_ROOT, &cgrp->flags))
@@ -10064,14 +10064,14 @@ int cpu_cgroup_proc_loadavg(struct
cgroup_subsys_state *css,
* overhead for activate/deactivate operations. So, we
* don't account child cgroup unint tasks here.
*/
- nr_running += tg->cfs_rq[i]->nr_unint;
+ nr_running += (long)tg->cfs_rq[i]->nr_unint;
#endif
#ifdef CONFIG_RT_GROUP_SCHED
nr_running += tg->rt_rq[i]->rt_nr_running;
#endif
}
- seq_printf(p, "%lu.%02lu %lu.%02lu %lu.%02lu %d/%d %d\n",
+ seq_printf(p, "%lu.%02lu %lu.%02lu %lu.%02lu %ld/%d %d\n",
LOAD_INT(avnrun[0]), LOAD_FRAC(avnrun[0]),
LOAD_INT(avnrun[1]), LOAD_FRAC(avnrun[1]),
LOAD_INT(avnrun[2]), LOAD_FRAC(avnrun[2]),
--
2.47.1
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