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From:   Prateek Sood <prsood@codeaurora.org>
To:     tj@kernel.org, avagin@gmail.com, mingo@kernel.org,
        peterz@infradead.org
Cc:     linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        sramana@codeaurora.org, Prateek Sood <prsood@codeaurora.org>
Subject: [PATCH] cgroup/cpuset: fix circular locking dependency
Date:   Tue, 28 Nov 2017 17:05:46 +0530
Message-Id: <1511868946-23959-1-git-send-email-prsood@codeaurora.org>
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CPU1
cpus_read_lock+0x3e/0x80
static_key_slow_inc+0xe/0xa0
cpuset_css_online+0x62/0x330
online_css+0x26/0x80
cgroup_apply_control_enable+0x266/0x3d0
cgroup_mkdir+0x37d/0x4f0
kernfs_iop_mkdir+0x53/0x80
vfs_mkdir+0x10e/0x1a0
SyS_mkdirat+0xb3/0xe0
entry_SYSCALL_64_fastpath+0x23/0x9a

CPU0
lock_acquire+0xec/0x1e0
__mutex_lock+0x89/0x920
cpuset_write_resmask+0x61/0x1100
cgroup_file_write+0x7b/0x200
kernfs_fop_write+0x112/0x1a0
__vfs_write+0x23/0x150
vfs_write+0xc8/0x1c0
SyS_write+0x45/0xa0
entry_SYSCALL_64_fastpath+0x23/0x9a

CPU0                               CPU1
----                               ----
lock(cpu_hotplug_lock.rw_sem);
                                lock(cpuset_mutex);
                                lock(cpu_hotplug_lock.rw_sem);
lock(cpuset_mutex);

Change locking order of cpu_hotplug_lock.rw_sem and
cpuset_mutex in cpuset_css_online(). Use _cpuslocked()
version for static_branch_inc/static_branch_dec in
cpuset_inc()/cpuset_dec().

Signed-off-by: Prateek Sood <prsood@codeaurora.org>
---
 include/linux/cpuset.h     |  8 ++++----
 include/linux/jump_label.h | 10 ++++++++--
 kernel/cgroup/cpuset.c     |  4 ++--
 kernel/jump_label.c        | 13 +++++++++++++
 4 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 2ab910f..5aadc25 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -40,14 +40,14 @@ static inline bool cpusets_enabled(void)
 
 static inline void cpuset_inc(void)
 {
-	static_branch_inc(&cpusets_pre_enable_key);
-	static_branch_inc(&cpusets_enabled_key);
+	static_branch_inc_cpuslocked(&cpusets_pre_enable_key);
+	static_branch_inc_cpuslocked(&cpusets_enabled_key);
 }
 
 static inline void cpuset_dec(void)
 {
-	static_branch_dec(&cpusets_enabled_key);
-	static_branch_dec(&cpusets_pre_enable_key);
+	static_branch_dec_cpuslocked(&cpusets_enabled_key);
+	static_branch_dec_cpuslocked(&cpusets_pre_enable_key);
 }
 
 extern int cpuset_init(void);
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index c7b368c..890e21c 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -160,6 +160,8 @@ extern void arch_jump_label_transform_static(struct jump_entry *entry,
 extern int jump_label_text_reserved(void *start, void *end);
 extern void static_key_slow_inc(struct static_key *key);
 extern void static_key_slow_dec(struct static_key *key);
+extern void static_key_slow_incr_cpuslocked(struct static_key *key);
+extern void static_key_slow_decr_cpuslocked(struct static_key *key);
 extern void jump_label_apply_nops(struct module *mod);
 extern int static_key_count(struct static_key *key);
 extern void static_key_enable(struct static_key *key);
@@ -259,6 +261,8 @@ static inline void static_key_disable(struct static_key *key)
 
 #define static_key_enable_cpuslocked(k)		static_key_enable((k))
 #define static_key_disable_cpuslocked(k)	static_key_disable((k))
+#define static_key_slow_incr_cpuslocked(k)	static_key_slow_inc((k))
+#define static_key_slow_decr_cpuslocked(k)	static_key_slow_dec((k))
 
 #define STATIC_KEY_INIT_TRUE	{ .enabled = ATOMIC_INIT(1) }
 #define STATIC_KEY_INIT_FALSE	{ .enabled = ATOMIC_INIT(0) }
@@ -414,8 +418,10 @@ struct static_key_false {
  * Advanced usage; refcount, branch is enabled when: count != 0
  */
 
-#define static_branch_inc(x)		static_key_slow_inc(&(x)->key)
-#define static_branch_dec(x)		static_key_slow_dec(&(x)->key)
+#define static_branch_inc(x)			static_key_slow_inc(&(x)->key)
+#define static_branch_dec(x)			static_key_slow_dec(&(x)->key)
+#define static_branch_inc_cpuslocked(x)		static_key_slow_incr_cpuslocked(&(x)->key)
+#define static_branch_dec_cpuslocked(x)		static_key_slow_decr_cpuslocked(&(x)->key)
 
 /*
  * Normal usage; boolean enable/disable.
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 227bc25..4ad8bae 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1985,7 +1985,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 	if (!parent)
 		return 0;
 
-	mutex_lock(&cpuset_mutex);
+	cpuset_sched_change_begin();
 
 	set_bit(CS_ONLINE, &cs->flags);
 	if (is_spread_page(parent))
@@ -2034,7 +2034,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 	cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
 	spin_unlock_irq(&callback_lock);
 out_unlock:
-	mutex_unlock(&cpuset_mutex);
+	cpuset_sched_change_end();
 	return 0;
 }
 
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 8594d24..dde0eaa 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -126,6 +126,12 @@ void static_key_slow_inc(struct static_key *key)
 }
 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 
+void static_key_slow_incr_cpuslocked(struct static_key *key)
+{
+	static_key_slow_inc_cpuslocked(key);
+}
+EXPORT_SYMBOL_GPL(static_key_slow_incr_cpuslocked);
+
 void static_key_enable_cpuslocked(struct static_key *key)
 {
 	STATIC_KEY_CHECK_USE(key);
@@ -229,6 +235,13 @@ void static_key_slow_dec(struct static_key *key)
 }
 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 
+void static_key_slow_decr_cpuslocked(struct static_key *key)
+{
+	STATIC_KEY_CHECK_USE(key);
+	static_key_slow_dec_cpuslocked(key, 0, NULL);
+}
+EXPORT_SYMBOL_GPL(static_key_slow_decr_cpuslocked);
+
 void static_key_slow_dec_deferred(struct static_key_deferred *key)
 {
 	STATIC_KEY_CHECK_USE(key);
-- 
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is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.


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