Commit 0b18d318 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

[S390] smp: Fix locking order. 



On some smp sysfs store attributes get_online_cpus() may block on
cpu_hotplug.lock, but we hold already smp_cpu_state_mutex. Since the
locking order on cpu hotplug via arch_update_cpu_topology is inverse
this might lead to deadlocks.
So make sure locking order is always the same.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent f291e172

arch/s390/kernel/smp.c

+6 −6
Original line number Diff line number Diff line
@@ -890,8 +890,8 @@ static ssize_t cpu_configure_store(struct sys_device *dev, const char *buf, 
	if (val != 0 && val != 1)

		return -EINVAL;



	mutex_lock(&smp_cpu_state_mutex);

	get_online_cpus();

	mutex_lock(&smp_cpu_state_mutex);

	rc = -EBUSY;

	if (cpu_online(cpu))

		goto out;
@@ -919,8 +919,8 @@ static ssize_t cpu_configure_store(struct sys_device *dev, const char *buf, 
		break;

	}

out:

	put_online_cpus();

	mutex_unlock(&smp_cpu_state_mutex);

	put_online_cpus();

	return rc ? rc : count;

}

static SYSDEV_ATTR(configure, 0644, cpu_configure_show, cpu_configure_store);
@@ -1095,8 +1095,8 @@ static ssize_t __ref rescan_store(struct sys_device *dev, 
	int cpu;

	int rc;



	mutex_lock(&smp_cpu_state_mutex);

	get_online_cpus();

	mutex_lock(&smp_cpu_state_mutex);

	newcpus = cpu_present_map;

	rc = smp_rescan_cpus();

	if (rc)
@@ -1109,8 +1109,8 @@ static ssize_t __ref rescan_store(struct sys_device *dev, 
	}

	rc = 0;

out:

	put_online_cpus();

	mutex_unlock(&smp_cpu_state_mutex);

	put_online_cpus();

	if (!cpus_empty(newcpus))

		topology_schedule_update();

	return rc ? rc : count;
@@ -1139,16 +1139,16 @@ static ssize_t dispatching_store(struct sys_device *dev, const char *buf, 
	if (val != 0 && val != 1)

		return -EINVAL;

	rc = 0;

	mutex_lock(&smp_cpu_state_mutex);

	get_online_cpus();

	mutex_lock(&smp_cpu_state_mutex);

	if (cpu_management == val)

		goto out;

	rc = topology_set_cpu_management(val);

	if (!rc)

		cpu_management = val;

out:

	put_online_cpus();

	mutex_unlock(&smp_cpu_state_mutex);

	put_online_cpus();

	return rc ? rc : count;

}

static SYSDEV_ATTR(dispatching, 0644, dispatching_show, dispatching_store);

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