[PATCH 4.14 068/146] sched/core: Fix cpu.max vs. cpuhotplug deadlock

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra pet...@infradead.org

commit ce48c146495a1a50e48cdbfbfaba3e708be7c07c upstream

Tejun reported the following cpu-hotplug lock (percpu-rwsem) read recursion:

  tg_set_cfs_bandwidth()
    get_online_cpus()
      cpus_read_lock()

    cfs_bandwidth_usage_inc()
      static_key_slow_inc()
        cpus_read_lock()

Reported-by: Tejun Heo <t...@kernel.org>
Tested-by: Tejun Heo <t...@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Link: http://lkml.kernel.org/r/20180122215328.GP3397@worktop
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 include/linux/jump_label.h |    7 +++++++
 kernel/jump_label.c        |   12 +++++++++---
 kernel/sched/fair.c        |    4 ++--
 3 files changed, 18 insertions(+), 5 deletions(-)

--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -160,6 +160,8 @@ extern void arch_jump_label_transform_st
 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_inc_cpuslocked(struct static_key *key);
+extern void static_key_slow_dec_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);
@@ -222,6 +224,9 @@ static inline void static_key_slow_dec(s
        atomic_dec(&key->enabled);
 }
 
+#define static_key_slow_inc_cpuslocked(key) static_key_slow_inc(key)
+#define static_key_slow_dec_cpuslocked(key) static_key_slow_dec(key)
+
 static inline int jump_label_text_reserved(void *start, void *end)
 {
        return 0;
@@ -416,6 +421,8 @@ extern bool ____wrong_branch_error(void)
 
 #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_inc_cpuslocked(&(x)->key)
+#define static_branch_dec_cpuslocked(x)        
static_key_slow_dec_cpuslocked(&(x)->key)
 
 /*
  * Normal usage; boolean enable/disable.
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -79,7 +79,7 @@ int static_key_count(struct static_key *
 }
 EXPORT_SYMBOL_GPL(static_key_count);
 
-static void static_key_slow_inc_cpuslocked(struct static_key *key)
+void static_key_slow_inc_cpuslocked(struct static_key *key)
 {
        int v, v1;
 
@@ -180,7 +180,7 @@ void static_key_disable(struct static_ke
 }
 EXPORT_SYMBOL_GPL(static_key_disable);
 
-static void static_key_slow_dec_cpuslocked(struct static_key *key,
+static void __static_key_slow_dec_cpuslocked(struct static_key *key,
                                           unsigned long rate_limit,
                                           struct delayed_work *work)
 {
@@ -211,7 +211,7 @@ static void __static_key_slow_dec(struct
                                  struct delayed_work *work)
 {
        cpus_read_lock();
-       static_key_slow_dec_cpuslocked(key, rate_limit, work);
+       __static_key_slow_dec_cpuslocked(key, rate_limit, work);
        cpus_read_unlock();
 }
 
@@ -229,6 +229,12 @@ void static_key_slow_dec(struct static_k
 }
 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 
+void static_key_slow_dec_cpuslocked(struct static_key *key)
+{
+       STATIC_KEY_CHECK_USE();
+       __static_key_slow_dec_cpuslocked(key, 0, NULL);
+}
+
 void static_key_slow_dec_deferred(struct static_key_deferred *key)
 {
        STATIC_KEY_CHECK_USE();
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4040,12 +4040,12 @@ static inline bool cfs_bandwidth_used(vo
 
 void cfs_bandwidth_usage_inc(void)
 {
-       static_key_slow_inc(&__cfs_bandwidth_used);
+       static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
 }
 
 void cfs_bandwidth_usage_dec(void)
 {
-       static_key_slow_dec(&__cfs_bandwidth_used);
+       static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
 }
 #else /* HAVE_JUMP_LABEL */
 static bool cfs_bandwidth_used(void)