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Subject[PATCH 02/12] cpu-hotplug: return better errno on cpu hotplug failure
Date
Currently, onlining or offlining a CPU failure by one of the cpu
notifiers error always cause -EINVAL error.
(i.e. writing 0 or 1 to /sys/devices/system/cpu/cpuX/online gets EINVAL)

To get better error reporting rather than always getting -EINVAL,
This changes cpu_notify() to return -errno value with notifier_to_errno() and
fix the callers. Now that cpu notifiers can return encapsulate errno value.

Currently, all cpu hotplug notifiers return NOTIFY_OK, NOTIFY_BAD,
or NOTIFY_DONE. So cpu_notify() can returns 0 or -EPERM with this change
for now.
(notifier_to_errno(NOTIFY_OK) == 0, notifier_to_errno(NOTIFY_DONE) == 0,
notifier_to_errno(NOTIFY_BAD) == -EPERM)

Forthcoming patches convert several cpu notifiers to return encapsulate
errno value with notifier_from_errno().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
---
kernel/cpu.c | 14 ++++++++------
1 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index bc9c301..d3f335e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -136,8 +136,12 @@ int __ref register_cpu_notifier(struct notifier_block *nb)
static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
int *nr_calls)
{
- return __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
+ int ret;
+
+ ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
nr_calls);
+
+ return notifier_to_errno(ret);
}

static int cpu_notify(unsigned long val, void *v)
@@ -150,7 +154,7 @@ static void cpu_notify_nofail(unsigned long val, void *v)
int err;

err = cpu_notify(val, v);
- BUG_ON(err == NOTIFY_BAD);
+ BUG_ON(err);
}

#ifdef CONFIG_HOTPLUG_CPU
@@ -230,14 +234,13 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
cpu_hotplug_begin();
set_cpu_active(cpu, false);
err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
- if (err == NOTIFY_BAD) {
+ if (err) {
set_cpu_active(cpu, true);

nr_calls--;
__cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
printk("%s: attempt to take down CPU %u failed\n",
__func__, cpu);
- err = -EINVAL;
goto out_release;
}

@@ -314,11 +317,10 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)

cpu_hotplug_begin();
ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
- if (ret == NOTIFY_BAD) {
+ if (ret) {
nr_calls--;
printk("%s: attempt to bring up CPU %u failed\n",
__func__, cpu);
- ret = -EINVAL;
goto out_notify;
}

--
1.6.0.6


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