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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: Tejun Heo <tj@kernel.org>
Tested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Peter Zijlstra 2018-01-22 22:53:28 +01:00 committed by Ingo Molnar
parent 1f07476ec1
commit ce48c14649
3 changed files with 18 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/jump_label.h
View File

@ -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.

12
kernel/jump_label.c
View File

@ -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);

4
kernel/sched/fair.c
View File

@ -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)