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cpu/hotplug: Make wait for dead cpu completion based

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Kill the busy spinning on the control side and just wait for the hotplugged
cpu to tell that it reached the dead state.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.776157858@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2016-02-26 18:43:43 +00:00
parent 8df3e07e7f
commit e69aab1311
4 changed files with 17 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/cpu.h
View File

@ -276,14 +276,15 @@ void arch_cpu_idle_enter(void);
void arch_cpu_idle_exit(void);
void arch_cpu_idle_dead(void);
DECLARE_PER_CPU(bool, cpu_dead_idle);
int cpu_report_state(int cpu);
int cpu_check_up_prepare(int cpu);
void cpu_set_state_online(int cpu);
#ifdef CONFIG_HOTPLUG_CPU
bool cpu_wait_death(unsigned int cpu, int seconds);
bool cpu_report_death(void);
void cpuhp_report_idle_dead(void);
#else
static inline void cpuhp_report_idle_dead(void) { }
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
#endif /* _LINUX_CPU_H_ */

1
include/linux/cpuhotplug.h
View File

@ -6,6 +6,7 @@ enum cpuhp_state {
CPUHP_CREATE_THREADS,
CPUHP_NOTIFY_PREPARE,
CPUHP_BRINGUP_CPU,
CPUHP_AP_IDLE_DEAD,
CPUHP_AP_OFFLINE,
CPUHP_AP_NOTIFY_STARTING,
CPUHP_AP_ONLINE,

16
kernel/cpu.c
View File

@ -688,6 +688,7 @@ static int take_cpu_down(void *_param)
static int takedown_cpu(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
int err;
/*
@ -733,10 +734,8 @@ static int takedown_cpu(unsigned int cpu)
*
* Wait for the stop thread to go away.
*/
while (!per_cpu(cpu_dead_idle, cpu))
cpu_relax();
smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
per_cpu(cpu_dead_idle, cpu) = false;
wait_for_completion(&st->done);
BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
/* Interrupts are moved away from the dying cpu, reenable alloc/free */
irq_unlock_sparse();
@ -756,6 +755,15 @@ static int notify_dead(unsigned int cpu)
return 0;
}
void cpuhp_report_idle_dead(void)
{
struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
BUG_ON(st->state != CPUHP_AP_OFFLINE);
st->state = CPUHP_AP_IDLE_DEAD;
complete(&st->done);
}
#else
#define notify_down_prepare NULL
#define takedown_cpu NULL

5
kernel/sched/idle.c
View File

@ -194,8 +194,6 @@ exit_idle:
rcu_idle_exit();
}
DEFINE_PER_CPU(bool, cpu_dead_idle);
/*
* Generic idle loop implementation
*
@ -224,8 +222,7 @@ static void cpu_idle_loop(void)
if (cpu_is_offline(smp_processor_id())) {
rcu_cpu_notify(NULL, CPU_DYING_IDLE,
(void *)(long)smp_processor_id());
smp_mb(); /* all activity before dead. */
this_cpu_write(cpu_dead_idle, true);
cpuhp_report_idle_dead();
arch_cpu_idle_dead();
}