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A small set of updates for CPU hotplug:

Browse source 
- Prevent stale CPU hotplug state in the cpu_down() path which
     was detected by stress testing the sysfs interface
 
   - Ensure that the target CPU hotplug state for the boot CPU is
     CPUHP_ONLINE instead of the compile time init value CPUHP_OFFLINE.
 
   - Switch back to the original behaviour of warning when a CPU hotplug
     callback in the DYING/STARTING section returns an error code. Otherwise
     a buggy callback can leave the CPUs in an non recoverable state.
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Merge tag 'smp-core-2022-12-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull CPU hotplug updates from Thomas Gleixner:
 "A small set of updates for CPU hotplug:

   - Prevent stale CPU hotplug state in the cpu_down() path which was
     detected by stress testing the sysfs interface

   - Ensure that the target CPU hotplug state for the boot CPU is
     CPUHP_ONLINE instead of the compile time init value CPUHP_OFFLINE.

   - Switch back to the original behaviour of warning when a CPU hotplug
     callback in the DYING/STARTING section returns an error code.

     Otherwise a buggy callback can leave the CPUs in an non recoverable
     state"

* tag 'smp-core-2022-12-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu/hotplug: Do not bail-out in DYING/STARTING sections
  cpu/hotplug: Set cpuhp target for boot cpu
  cpu/hotplug: Make target_store() a nop when target == state
This commit is contained in:
Linus Torvalds 2022-12-12 11:56:59 -08:00
commit 08d72bd299
1 changed files with 44 additions and 17 deletions
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61
kernel/cpu.c
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@ -663,21 +663,51 @@ static bool cpuhp_next_state(bool bringup,
return true;
}
static int cpuhp_invoke_callback_range(bool bringup,
unsigned int cpu,
struct cpuhp_cpu_state *st,
enum cpuhp_state target)
static int __cpuhp_invoke_callback_range(bool bringup,
unsigned int cpu,
struct cpuhp_cpu_state *st,
enum cpuhp_state target,
bool nofail)
{
enum cpuhp_state state;
int err = 0;
int ret = 0;
while (cpuhp_next_state(bringup, &state, st, target)) {
int err;
err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
if (err)
if (!err)
continue;
if (nofail) {
pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
cpu, bringup ? "UP" : "DOWN",
cpuhp_get_step(st->state)->name,
st->state, err);
ret = -1;
} else {
ret = err;
break;
}
}
return err;
return ret;
}
static inline int cpuhp_invoke_callback_range(bool bringup,
unsigned int cpu,
struct cpuhp_cpu_state *st,
enum cpuhp_state target)
{
return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
}
static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
unsigned int cpu,
struct cpuhp_cpu_state *st,
enum cpuhp_state target)
{
__cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
}
static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
@ -999,7 +1029,6 @@ static int take_cpu_down(void *_param)
struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
int err, cpu = smp_processor_id();
int ret;
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable();
@ -1012,13 +1041,10 @@ static int take_cpu_down(void *_param)
*/
WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
/* Invoke the former CPU_DYING callbacks */
ret = cpuhp_invoke_callback_range(false, cpu, st, target);
/*
* DYING must not fail!
* Invoke the former CPU_DYING callbacks. DYING must not fail!
*/
WARN_ON_ONCE(ret);
cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
/* Give up timekeeping duties */
tick_handover_do_timer();
@ -1296,16 +1322,14 @@ void notify_cpu_starting(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
int ret;
rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
cpumask_set_cpu(cpu, &cpus_booted_once_mask);
ret = cpuhp_invoke_callback_range(true, cpu, st, target);
/*
* STARTING must not fail!
*/
WARN_ON_ONCE(ret);
cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
}
/*
@ -2326,8 +2350,10 @@ static ssize_t target_store(struct device *dev, struct device_attribute *attr,
if (st->state < target)
ret = cpu_up(dev->id, target);
else
else if (st->state > target)
ret = cpu_down(dev->id, target);
else if (WARN_ON(st->target != target))
st->target = target;
out:
unlock_device_hotplug();
return ret ? ret : count;
@ -2688,6 +2714,7 @@ void __init boot_cpu_hotplug_init(void)
cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
#endif
this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
}
/*