[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: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 0dfa988c1b26..6bb5c050640f 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -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);