Ensure that the trap handler is regisstered only once.

Register with first use,

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>

diff --git a/dtrace/dtrace_dev.c b/dtrace/dtrace_dev.c
index acb8af843dd28d290bb5817dc0a6065ccdba27a8..c3e76af41f0e78ee6a7026efb1946592c5175100 100644 (file)
--- a/dtrace/dtrace_dev.c
+++ b/dtrace/dtrace_dev.c
@@ -896,6 +896,15 @@ static int dtrace_open(struct inode *inode, struct file *file)
 
        file->private_data = state;
 
+       /*
+        * We only want to enable trap handling once, so we'll do it for the
+        * first open of the DTrace core device file.
+        * FIXME: If anonymous tracing is enabled, that would have enabled trap
+        *        handling already, so we should not do it here again.
+        */
+       if (dtrace_opens == 1)
+               dtrace_enable();
+
        mutex_unlock(&dtrace_lock);
 
        return 0;
@@ -924,7 +933,15 @@ static int dtrace_close(struct inode *inode, struct file *file)
        if (--dtrace_opens == 0 && dtrace_anon.dta_enabling == NULL)
                (void)kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
 #else
-       --dtrace_opens;
+       /*
+        * Once the last user of DTrace is gone, we can safely disable trap
+        * handling.
+        * FIXME: We should not disable it if anonymous tracing is enabled as
+        *        we still have probes running in that case even without any
+        *        client holding the device file open.
+        */
+       if (--dtrace_opens == 0)
+               dtrace_disable();
 #endif
 
        mutex_unlock(&dtrace_lock);
@@ -1299,8 +1316,6 @@ int dtrace_dev_init(void)
         * the first provider causing the core to be loaded.
         */
 #endif
-       dtrace_enable();
-
        mutex_unlock(&dtrace_provider_lock);
        mutex_unlock(&dtrace_lock);
 
@@ -1309,8 +1324,6 @@ int dtrace_dev_init(void)
 
 void dtrace_dev_exit(void)
 {
-       dtrace_disable();
-
        kmem_cache_destroy(dtrace_state_cache);
        misc_deregister(&dtrace_dev);