[S390] cio: fix parallel cm_enable processing.

It is now possible to trigger cm_enable processing several times in
parallel without causing a kernel panic.

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

2 files changed, 9 insertions, 4 deletions

diff --git a/drivers/s390/cio/chsc.c b/drivers/s390/cio/chsc.c
index b6a40c20780d..5de86908b0d0 100644
--- a/drivers/s390/cio/chsc.c
+++ b/drivers/s390/cio/chsc.c
@@ -766,7 +766,6 @@ chsc_secm(struct channel_subsystem *css, int enable)
         if (!secm_area)
                 return -ENOMEM;
 
-        mutex_lock(&css->mutex);
         if (enable && !css->cm_enabled) {
                 css->cub_addr1 = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
                 css->cub_addr2 = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
@@ -774,7 +773,6 @@ chsc_secm(struct channel_subsystem *css, int enable)
                         free_page((unsigned long)css->cub_addr1);
                         free_page((unsigned long)css->cub_addr2);
                         free_page((unsigned long)secm_area);
-                        mutex_unlock(&css->mutex);
                         return -ENOMEM;
                 }
         }
@@ -795,7 +793,6 @@ chsc_secm(struct channel_subsystem *css, int enable)
                 free_page((unsigned long)css->cub_addr1);
                 free_page((unsigned long)css->cub_addr2);
         }
-        mutex_unlock(&css->mutex);
         free_page((unsigned long)secm_area);
         return ret;
 }
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 3e829c827493..c1afab5f72d6 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -689,10 +689,14 @@ css_cm_enable_show(struct device *dev, struct device_attribute *attr,
                    char *buf)
 {
         struct channel_subsystem *css = to_css(dev);
+        int ret;
 
         if (!css)
                 return 0;
-        return sprintf(buf, "%x\n", css->cm_enabled);
+        mutex_lock(&css->mutex);
+        ret = sprintf(buf, "%x\n", css->cm_enabled);
+        mutex_unlock(&css->mutex);
+        return ret;
 }
 
 static ssize_t
@@ -702,6 +706,7 @@ css_cm_enable_store(struct device *dev, struct device_attribute *attr,
         struct channel_subsystem *css = to_css(dev);
         int ret;
 
+        mutex_lock(&css->mutex);
         switch (buf[0]) {
         case '0':
                 ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
@@ -712,6 +717,7 @@ css_cm_enable_store(struct device *dev, struct device_attribute *attr,
         default:
                 ret = -EINVAL;
         }
+        mutex_unlock(&css->mutex);
         return ret < 0 ? ret : count;
 }
 
@@ -758,9 +764,11 @@ static int css_reboot_event(struct notifier_block *this,
                 struct channel_subsystem *css;
 
                 css = channel_subsystems[i];
+                mutex_lock(&css->mutex);
                 if (css->cm_enabled)
                         if (chsc_secm(css, 0))
                                 ret = NOTIFY_BAD;
+                mutex_unlock(&css->mutex);
         }
 
         return ret;