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

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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>
This commit is contained in:
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
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4
kernel/sched/fair.c
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@@ -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)