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net/iucv/iucv.c: Fix CPU hotplug callback registration
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Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_notifier_register_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_notifier_register_done();

Fix the code in net/iucv/iucv.c by using this latter form of callback
registration. Also, provide helper functions to perform the common memory
allocations and frees, to condense repetitive code.

Cc: Ursula Braun <[email protected]>
Cc: Ingo Molnar <[email protected]>
Acked-by: David S. Miller <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>
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@rafaeljw
Srivatsa S. Bhat authored and rafaeljw committed Mar 20, 2014
1 parent e30a293 commit a0e247a
Showing 1 changed file with 57 additions and 64 deletions.
121 changes: 57 additions & 64 deletions net/iucv/iucv.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -621,6 +621,42 @@ static void iucv_disable(void)
put_online_cpus();
}

static void free_iucv_data(int cpu)
{
kfree(iucv_param_irq[cpu]);
iucv_param_irq[cpu] = NULL;
kfree(iucv_param[cpu]);
iucv_param[cpu] = NULL;
kfree(iucv_irq_data[cpu]);
iucv_irq_data[cpu] = NULL;
}

static int alloc_iucv_data(int cpu)
{
/* Note: GFP_DMA used to get memory below 2G */
iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_irq_data[cpu])
goto out_free;

/* Allocate parameter blocks. */
iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_param[cpu])
goto out_free;

iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_param_irq[cpu])
goto out_free;

return 0;

out_free:
free_iucv_data(cpu);
return -ENOMEM;
}

static int iucv_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
Expand All @@ -630,38 +666,14 @@ static int iucv_cpu_notify(struct notifier_block *self,
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_irq_data[cpu])
return notifier_from_errno(-ENOMEM);

iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_param[cpu]) {
kfree(iucv_irq_data[cpu]);
iucv_irq_data[cpu] = NULL;
if (alloc_iucv_data(cpu))
return notifier_from_errno(-ENOMEM);
}
iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_param_irq[cpu]) {
kfree(iucv_param[cpu]);
iucv_param[cpu] = NULL;
kfree(iucv_irq_data[cpu]);
iucv_irq_data[cpu] = NULL;
return notifier_from_errno(-ENOMEM);
}
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DEAD:
case CPU_DEAD_FROZEN:
kfree(iucv_param_irq[cpu]);
iucv_param_irq[cpu] = NULL;
kfree(iucv_param[cpu]);
iucv_param[cpu] = NULL;
kfree(iucv_irq_data[cpu]);
iucv_irq_data[cpu] = NULL;
free_iucv_data(cpu);
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
Expand Down Expand Up @@ -2025,33 +2037,20 @@ static int __init iucv_init(void)
goto out_int;
}

for_each_online_cpu(cpu) {
/* Note: GFP_DMA used to get memory below 2G */
iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_irq_data[cpu]) {
rc = -ENOMEM;
goto out_free;
}
cpu_notifier_register_begin();

/* Allocate parameter blocks. */
iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_param[cpu]) {
rc = -ENOMEM;
goto out_free;
}
iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
if (!iucv_param_irq[cpu]) {
for_each_online_cpu(cpu) {
if (alloc_iucv_data(cpu)) {
rc = -ENOMEM;
goto out_free;
}

}
rc = register_hotcpu_notifier(&iucv_cpu_notifier);
rc = __register_hotcpu_notifier(&iucv_cpu_notifier);
if (rc)
goto out_free;

cpu_notifier_register_done();

rc = register_reboot_notifier(&iucv_reboot_notifier);
if (rc)
goto out_cpu;
Expand All @@ -2069,16 +2068,14 @@ static int __init iucv_init(void)
out_reboot:
unregister_reboot_notifier(&iucv_reboot_notifier);
out_cpu:
unregister_hotcpu_notifier(&iucv_cpu_notifier);
cpu_notifier_register_begin();
__unregister_hotcpu_notifier(&iucv_cpu_notifier);
out_free:
for_each_possible_cpu(cpu) {
kfree(iucv_param_irq[cpu]);
iucv_param_irq[cpu] = NULL;
kfree(iucv_param[cpu]);
iucv_param[cpu] = NULL;
kfree(iucv_irq_data[cpu]);
iucv_irq_data[cpu] = NULL;
}
for_each_possible_cpu(cpu)
free_iucv_data(cpu);

cpu_notifier_register_done();

root_device_unregister(iucv_root);
out_int:
unregister_external_interrupt(0x4000, iucv_external_interrupt);
Expand All @@ -2105,15 +2102,11 @@ static void __exit iucv_exit(void)
kfree(p);
spin_unlock_irq(&iucv_queue_lock);
unregister_reboot_notifier(&iucv_reboot_notifier);
unregister_hotcpu_notifier(&iucv_cpu_notifier);
for_each_possible_cpu(cpu) {
kfree(iucv_param_irq[cpu]);
iucv_param_irq[cpu] = NULL;
kfree(iucv_param[cpu]);
iucv_param[cpu] = NULL;
kfree(iucv_irq_data[cpu]);
iucv_irq_data[cpu] = NULL;
}
cpu_notifier_register_begin();
__unregister_hotcpu_notifier(&iucv_cpu_notifier);
for_each_possible_cpu(cpu)
free_iucv_data(cpu);
cpu_notifier_register_done();
root_device_unregister(iucv_root);
bus_unregister(&iucv_bus);
unregister_external_interrupt(0x4000, iucv_external_interrupt);
Expand Down

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