diff options
| author | Qais Yousef <qais.yousef@arm.com> | 2021-05-10 15:50:32 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-05-19 10:53:02 +0200 |
| commit | 93b73858701fd01de26a4a874eb95f9b7156fd4b (patch) | |
| tree | b32f97678796f331182efde3cf03a69683e02cba /kernel/sched | |
| parent | 0c18f2ecfcc274a4bcc1d122f79ebd4001c3b445 (diff) | |
sched/uclamp: Fix locking around cpu_util_update_eff()
cpu_cgroup_css_online() calls cpu_util_update_eff() without holding the
uclamp_mutex or rcu_read_lock() like other call sites, which is
a mistake.
The uclamp_mutex is required to protect against concurrent reads and
writes that could update the cgroup hierarchy.
The rcu_read_lock() is required to traverse the cgroup data structures
in cpu_util_update_eff().
Surround the caller with the required locks and add some asserts to
better document the dependency in cpu_util_update_eff().
Fixes: 7226017ad37a ("sched/uclamp: Fix a bug in propagating uclamp value in new cgroups")
Reported-by: Quentin Perret <qperret@google.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210510145032.1934078-3-qais.yousef@arm.com
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f97eb7323f36..3ec420c8a038 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -9507,7 +9507,11 @@ static int cpu_cgroup_css_online(struct cgroup_subsys_state *css) #ifdef CONFIG_UCLAMP_TASK_GROUP /* Propagate the effective uclamp value for the new group */ + mutex_lock(&uclamp_mutex); + rcu_read_lock(); cpu_util_update_eff(css); + rcu_read_unlock(); + mutex_unlock(&uclamp_mutex); #endif return 0; @@ -9597,6 +9601,9 @@ static void cpu_util_update_eff(struct cgroup_subsys_state *css) enum uclamp_id clamp_id; unsigned int clamps; + lockdep_assert_held(&uclamp_mutex); + SCHED_WARN_ON(!rcu_read_lock_held()); + css_for_each_descendant_pre(css, top_css) { uc_parent = css_tg(css)->parent ? css_tg(css)->parent->uclamp : NULL; |