[S390] cpu topology: fix locking

cpu_coregroup_map used to grab a mutex on s390 since it was only
called from process context.
Since c7c22e4d5c1fdebfac4dba76de7d0338c2b0d832 "block: add support
for IO CPU affinity" this is not true anymore.
It now also gets called from softirq context.

To prevent possible deadlocks change this in architecture code and
use a spinlock instead of a mutex.

Cc: stable@kernel.org
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index 632b13e10053..a947899dcba1 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -65,18 +65,21 @@ static int machine_has_topology_irq;
 static struct timer_list topology_timer;
 static void set_topology_timer(void);
 static DECLARE_WORK(topology_work, topology_work_fn);
+/* topology_lock protects the core linked list */
+static DEFINE_SPINLOCK(topology_lock);
 
 cpumask_t cpu_core_map[NR_CPUS];
 
 cpumask_t cpu_coregroup_map(unsigned int cpu)
 {
         struct core_info *core = &core_info;
+        unsigned long flags;
         cpumask_t mask;
 
         cpus_clear(mask);
         if (!machine_has_topology)
                 return cpu_present_map;
-        mutex_lock(&smp_cpu_state_mutex);
+        spin_lock_irqsave(&topology_lock, flags);
         while (core) {
                 if (cpu_isset(cpu, core->mask)) {
                         mask = core->mask;
@@ -84,7 +87,7 @@ cpumask_t cpu_coregroup_map(unsigned int cpu)
                 }
                 core = core->next;
         }
-        mutex_unlock(&smp_cpu_state_mutex);
+        spin_unlock_irqrestore(&topology_lock, flags);
         if (cpus_empty(mask))
                 mask = cpumask_of_cpu(cpu);
         return mask;
@@ -133,7 +136,7 @@ static void tl_to_cores(struct tl_info *info)
         union tl_entry *tle, *end;
         struct core_info *core = &core_info;
 
-        mutex_lock(&smp_cpu_state_mutex);
+        spin_lock_irq(&topology_lock);
         clear_cores();
         tle = info->tle;
         end = (union tl_entry *)((unsigned long)info + info->length);
@@ -157,7 +160,7 @@ static void tl_to_cores(struct tl_info *info)
                 }
                 tle = next_tle(tle);
         }
-        mutex_unlock(&smp_cpu_state_mutex);
+        spin_unlock_irq(&topology_lock);
 }
 
 static void topology_update_polarization_simple(void)