oprofile: disable write access to oprofilefs while profiler is running

Oprofile counters are setup when profiling is disabled. Thus, writing
to oprofilefs has no immediate effect. Changes are updated only after
oprofile is reenabled.

To keep userland and kernel states synchronized, we now allow
configuration of oprofile only if profiling is disabled.  In this case
it checks if the profiler is running and then disables write access to
oprofilefs by returning -EBUSY. The change should be backward
compatible with current oprofile userland daemon.

Acked-by: Maynard Johnson <maynardj@us.ibm.com>
Cc: William Cohen <wcohen@redhat.com>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>

4 files changed, 18 insertions, 20 deletions

diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
index b4a685719dba..f9bda64fcd1b 100644
--- a/drivers/oprofile/oprof.c
+++ b/drivers/oprofile/oprof.c
@@ -225,26 +225,17 @@ post_sync:
         mutex_unlock(&start_mutex);
 }
 
-int oprofile_set_backtrace(unsigned long val)
+int oprofile_set_ulong(unsigned long *addr, unsigned long val)
 {
-        int err = 0;
+        int err = -EBUSY;
 
         mutex_lock(&start_mutex);
-
-        if (oprofile_started) {
-                err = -EBUSY;
-                goto out;
+        if (!oprofile_started) {
+                *addr = val;
+                err = 0;
         }
-
-        if (!oprofile_ops.backtrace) {
-                err = -EINVAL;
-                goto out;
-        }
-
-        oprofile_backtrace_depth = val;
-
-out:
         mutex_unlock(&start_mutex);
+
         return err;
 }
 
diff --git a/drivers/oprofile/oprof.h b/drivers/oprofile/oprof.h
index 47e12cb4ee8b..177b73de5e5f 100644
--- a/drivers/oprofile/oprof.h
+++ b/drivers/oprofile/oprof.h
@@ -37,7 +37,7 @@ void oprofile_create_files(struct super_block *sb, struct dentry *root);
 int oprofile_timer_init(struct oprofile_operations *ops);
 void oprofile_timer_exit(void);
 
-int oprofile_set_backtrace(unsigned long depth);
+int oprofile_set_ulong(unsigned long *addr, unsigned long val);
 int oprofile_set_timeout(unsigned long time);
 
 #endif /* OPROF_H */
diff --git a/drivers/oprofile/oprofile_files.c b/drivers/oprofile/oprofile_files.c
index bbd7516e0869..ccf099e684a4 100644
--- a/drivers/oprofile/oprofile_files.c
+++ b/drivers/oprofile/oprofile_files.c
@@ -79,14 +79,17 @@ static ssize_t depth_write(struct file *file, char const __user *buf, size_t cou
         if (*offset)
                 return -EINVAL;
 
+        if (!oprofile_ops.backtrace)
+                return -EINVAL;
+
         retval = oprofilefs_ulong_from_user(&val, buf, count);
         if (retval)
                 return retval;
 
-        retval = oprofile_set_backtrace(val);
-
+        retval = oprofile_set_ulong(&oprofile_backtrace_depth, val);
         if (retval)
                 return retval;
+
         return count;
 }
 
diff --git a/drivers/oprofile/oprofilefs.c b/drivers/oprofile/oprofilefs.c
index 789a1a857ddf..1944621930d9 100644
--- a/drivers/oprofile/oprofilefs.c
+++ b/drivers/oprofile/oprofilefs.c
@@ -91,16 +91,20 @@ static ssize_t ulong_read_file(struct file *file, char __user *buf, size_t count
 
 static ssize_t ulong_write_file(struct file *file, char const __user *buf, size_t count, loff_t *offset)
 {
-        unsigned long *value = file->private_data;
+        unsigned long value;
         int retval;
 
         if (*offset)
                 return -EINVAL;
 
-        retval = oprofilefs_ulong_from_user(value, buf, count);
+        retval = oprofilefs_ulong_from_user(&value, buf, count);
+        if (retval)
+                return retval;
 
+        retval = oprofile_set_ulong(file->private_data, value);
         if (retval)
                 return retval;
+
         return count;
 }