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Commit ce48c146 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/core: Fix cpu.max vs. cpuhotplug deadlock 



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: default avatarTejun Heo <tj@kernel.org>
Tested-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180122215328.GP3397@worktop


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1f07476e

include/linux/jump_label.h

+7 −0
Original line number Diff line number Diff line
@@ -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_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(struct static_key *key) 
	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.

kernel/jump_label.c

+9 −3
Original line number Diff line number Diff line
@@ -79,7 +79,7 @@ int static_key_count(struct static_key *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_key *key) 
}

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 static_key *key, 
				  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_key *key) 
}

EXPORT_SYMBOL_GPL(static_key_slow_dec);



void static_key_slow_dec_cpuslocked(struct static_key *key)

{

	STATIC_KEY_CHECK_USE(key);

	__static_key_slow_dec_cpuslocked(key, 0, NULL);

}



void static_key_slow_dec_deferred(struct static_key_deferred *key)

{

	STATIC_KEY_CHECK_USE(key);

kernel/sched/fair.c

+2 −2
Original line number Diff line number Diff line
@@ -4365,12 +4365,12 @@ static inline bool cfs_bandwidth_used(void) 


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)