s390/pci: add locking for fmb access

Function measurement can be toggled at runtime. Make sure that
all access to the fmb is protected via a mutex.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 10 insertions, 6 deletions

diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index 281893864e1b..598f023cf8a6 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -827,6 +827,7 @@ int zpci_create_device(struct zpci_dev *zdev)
         if (rc)
                 goto out;
 
+        mutex_init(&zdev->lock);
         if (zdev->state == ZPCI_FN_STATE_CONFIGURED) {
                 rc = zpci_enable_device(zdev);
                 if (rc)
diff --git a/arch/s390/pci/pci_debug.c b/arch/s390/pci/pci_debug.c
index 97db1a411d54..3fc9b4d90b59 100644
--- a/arch/s390/pci/pci_debug.c
+++ b/arch/s390/pci/pci_debug.c
@@ -58,8 +58,12 @@ static int pci_perf_show(struct seq_file *m, void *v)
 
         if (!zdev)
                 return 0;
-        if (!zdev->fmb)
+
+        mutex_lock(&zdev->lock);
+        if (!zdev->fmb) {
+                mutex_unlock(&zdev->lock);
                 return seq_printf(m, "FMB statistics disabled\n");
+        }
 
         /* header */
         seq_printf(m, "FMB @ %p\n", zdev->fmb);
@@ -78,6 +82,7 @@ static int pci_perf_show(struct seq_file *m, void *v)
                                    pci_perf_names[i], *(stat + i));
 
         pci_sw_counter_show(m);
+        mutex_unlock(&zdev->lock);
         return 0;
 }
 
@@ -95,19 +100,17 @@ static ssize_t pci_perf_seq_write(struct file *file, const char __user *ubuf,
         if (rc)
                 return rc;
 
+        mutex_lock(&zdev->lock);
         switch (val) {
         case 0:
                 rc = zpci_fmb_disable_device(zdev);
-                if (rc)
-                        return rc;
                 break;
         case 1:
                 rc = zpci_fmb_enable_device(zdev);
-                if (rc)
-                        return rc;
                 break;
         }
-        return count;
+        mutex_unlock(&zdev->lock);
+        return rc ? rc : count;
 }
 
 static int pci_perf_seq_open(struct inode *inode, struct file *filp)