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authorAleksa Sarai <cyphar@cyphar.com>2019-10-17 02:50:01 +1100
committerTejun Heo <tj@kernel.org>2019-10-24 12:07:10 -0700
commita713af394cf382a30dd28a1015cbe572f1b9ca75 (patch)
treebe789f59b00a4a4a2bcbcdf3fd571f606e3cf1e2
parent1a99fcc035fb666f5d0909aef0a753284cb5d04c (diff)
cgroup: pids: use atomic64_t for pids->limit
Because pids->limit can be changed concurrently (but we don't want to take a lock because it would be needlessly expensive), use atomic64_ts instead. Fixes: commit 49b786ea146f ("cgroup: implement the PIDs subsystem") Cc: stable@vger.kernel.org # v4.3+ Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--kernel/cgroup/pids.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c
index 8e513a573fe9..138059eb730d 100644
--- a/kernel/cgroup/pids.c
+++ b/kernel/cgroup/pids.c
@@ -45,7 +45,7 @@ struct pids_cgroup {
* %PIDS_MAX = (%PID_MAX_LIMIT + 1).
*/
atomic64_t counter;
- int64_t limit;
+ atomic64_t limit;
/* Handle for "pids.events" */
struct cgroup_file events_file;
@@ -73,8 +73,8 @@ pids_css_alloc(struct cgroup_subsys_state *parent)
if (!pids)
return ERR_PTR(-ENOMEM);
- pids->limit = PIDS_MAX;
atomic64_set(&pids->counter, 0);
+ atomic64_set(&pids->limit, PIDS_MAX);
atomic64_set(&pids->events_limit, 0);
return &pids->css;
}
@@ -146,13 +146,14 @@ static int pids_try_charge(struct pids_cgroup *pids, int num)
for (p = pids; parent_pids(p); p = parent_pids(p)) {
int64_t new = atomic64_add_return(num, &p->counter);
+ int64_t limit = atomic64_read(&p->limit);
/*
* Since new is capped to the maximum number of pid_t, if
* p->limit is %PIDS_MAX then we know that this test will never
* fail.
*/
- if (new > p->limit)
+ if (new > limit)
goto revert;
}
@@ -277,7 +278,7 @@ set_limit:
* Limit updates don't need to be mutex'd, since it isn't
* critical that any racing fork()s follow the new limit.
*/
- pids->limit = limit;
+ atomic64_set(&pids->limit, limit);
return nbytes;
}
@@ -285,7 +286,7 @@ static int pids_max_show(struct seq_file *sf, void *v)
{
struct cgroup_subsys_state *css = seq_css(sf);
struct pids_cgroup *pids = css_pids(css);
- int64_t limit = pids->limit;
+ int64_t limit = atomic64_read(&pids->limit);
if (limit >= PIDS_MAX)
seq_printf(sf, "%s\n", PIDS_MAX_STR);