From: "tip-bot2 for Qais Yousef" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Quentin Perret <qperret@google.com>,
Qais Yousef <qais.yousef@arm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/core] sched/uclamp: Fix locking around cpu_util_update_eff()
Date: Wed, 19 May 2021 09:02:33 -0000 [thread overview]
Message-ID: <162141495356.29796.14241444686990774584.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210510145032.1934078-3-qais.yousef@arm.com>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 93b73858701fd01de26a4a874eb95f9b7156fd4b
Gitweb: https://git.kernel.org/tip/93b73858701fd01de26a4a874eb95f9b7156fd4b
Author: Qais Yousef <qais.yousef@arm.com>
AuthorDate: Mon, 10 May 2021 15:50:32 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 19 May 2021 10:53:02 +02:00
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
---
kernel/sched/core.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f97eb73..3ec420c 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;
next prev parent reply other threads:[~2021-05-19 9:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-10 14:50 [PATCH RESEND 0/2] Uclamp cgroup fixes Qais Yousef
2021-05-10 14:50 ` [PATCH RESEND 1/2] sched/uclamp: Fix wrong implementation of cpu.uclamp.min Qais Yousef
2021-05-19 8:09 ` [tip: sched/core] " tip-bot2 for Qais Yousef
2021-05-19 9:02 ` tip-bot2 for Qais Yousef
2021-05-10 14:50 ` [PATCH RESEND 2/2] sched/uclamp: Fix locking around cpu_util_update_eff() Qais Yousef
2021-05-19 8:09 ` [tip: sched/core] " tip-bot2 for Qais Yousef
2021-05-19 9:02 ` tip-bot2 for Qais Yousef [this message]
2021-05-13 14:13 ` [PATCH RESEND 0/2] Uclamp cgroup fixes Peter Zijlstra
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