ftdev: don't forget to disable events

Otherwise required buffers may not be present anymore.
This patch also fixes some minor initialization issues.

3 files changed, 57 insertions, 25 deletions

diff --git a/include/litmus/ftdev.h b/include/litmus/ftdev.h
index ac937fb733..8df916d1fc 100644
--- a/include/litmus/ftdev.h
+++ b/include/litmus/ftdev.h
@@ -16,11 +16,14 @@ struct ftdev;
 typedef int  (*ftdev_alloc_t)(struct ftdev* dev, unsigned int buf_no);
 typedef void (*ftdev_free_t)(struct ftdev* dev, unsigned int buf_no);
 
+struct ftdev_event;
+
 struct ftdev_minor {
         struct ft_buffer*       buf;
         unsigned int            readers;
         struct mutex            lock;
-        unsigned                active_events;
+        /* FIXME: filter for authorized events */
+        struct ftdev_event*     events;
 };
 
 struct ftdev {
@@ -28,7 +31,6 @@ struct ftdev {
         /* FIXME: don't waste memory, allocate dynamically */
         struct ftdev_minor      minor[MAX_FTDEV_MINORS];
         unsigned int            minor_cnt;
-        /* FIXME: track enabled/disabled events */
         ftdev_alloc_t           alloc;
         ftdev_free_t            free;
 };
@@ -36,7 +38,7 @@ struct ftdev {
 struct ft_buffer* alloc_ft_buffer(unsigned int count, size_t size);
 void free_ft_buffer(struct ft_buffer* buf);
 
-void ftdev_init(struct ftdev* ftdev);
+void ftdev_init(struct ftdev* ftdev, struct module* owner);
 int register_ftdev(struct ftdev* ftdev, const char* name, int major);
 
 #endif
diff --git a/litmus/ftdev.c b/litmus/ftdev.c
index 8e7d8e9dfe..fe3005db6d 100644
--- a/litmus/ftdev.c
+++ b/litmus/ftdev.c
@@ -58,6 +58,41 @@ void free_ft_buffer(struct ft_buffer* buf)
         }
 }
 
+struct ftdev_event {
+        int id;
+        struct ftdev_event* next;
+};
+
+static int activate(struct ftdev_event** chain, int id)
+{
+        struct ftdev_event* ev = kmalloc(sizeof(struct ftdev_event), GFP_KERNEL);
+        if (ev) {
+                printk(KERN_INFO
+                       "Enabling feather-trace event %d.\n", (int) id);
+                ft_enable_event(id);
+                ev->id = id;
+                ev->next = *chain;
+                *chain    = ev;
+        }
+        return ev ? 0 : -ENOMEM;
+}
+
+static void deactivate(struct ftdev_event** chain, int id)
+{
+        struct ftdev_event **last = chain;
+        struct ftdev_event *pos   = *chain;
+        while (pos) {
+                if (pos->id == id) {
+                        *last = pos->next;
+                        kfree(pos);
+                        printk(KERN_INFO
+                               "Disabling feather-trace event %d.\n", (int) id);
+                        ft_disable_event(id);
+                        break;
+                }
+        }
+}
+
 static int ftdev_open(struct inode *in, struct file *filp)
 {
         struct ftdev* ftdev;
@@ -110,8 +145,8 @@ static int ftdev_release(struct inode *in, struct file *filp)
         }
 
         if (ftdm->readers == 1) {
-                /*FIXME: disable events */
-                ftdm->active_events = 0;
+                while (ftdm->events)
+                        deactivate(&ftdm->events, ftdm->events->id);
 
                 /* wait for any pending events to complete */
                 set_current_state(TASK_UNINTERRUPTIBLE);
@@ -130,7 +165,7 @@ out:
         return err;
 }
 
-/* based on ft_buffer_read 
+/* based on ft_buffer_read
  * @returns < 0 : page fault
  *          = 0 : no data available
  *          = 1 : one slot copied
@@ -162,7 +197,7 @@ static ssize_t ftdev_read(struct file *filp,
                           char __user *to, size_t len, loff_t *f_pos)
 {
         /*      we ignore f_pos, this is strictly sequential */
-        
+
         ssize_t err = 0;
         size_t chunk;
         int copied;
@@ -181,7 +216,7 @@ static ssize_t ftdev_read(struct file *filp,
                         len    -= chunk;
                         to     += chunk;
                         err    += chunk;
-                } else if (copied == 0 && ftdm->active_events) {
+                } else if (copied == 0 && ftdm->events) {
                         /* only wait if there are any events enabled */
                         set_current_state(TASK_INTERRUPTIBLE);
                         schedule_timeout(50);
@@ -195,7 +230,7 @@ static ssize_t ftdev_read(struct file *filp,
                         /* page fault */
                         err = copied;
                         break;
-                } else 
+                } else
                         /* nothing left to get, return to user space */
                         break;
         }
@@ -239,19 +274,13 @@ static ssize_t ftdev_write(struct file *filp, const char __user *from,
                         goto out_unlock;
                 }
                 /* FIXME: check id against list of acceptable events */
-                /* FIXME: track which events must be disable at release time */
                 len  -= sizeof(cmd_t);
                 from += sizeof(cmd_t);
-                if (cmd == FTDEV_ENABLE_CMD) {
-                        printk(KERN_INFO
-                               "Disabling feather-trace event %d.\n", (int) id);
-                        ft_disable_event(id);
-                        ftdm->active_events--;
-                } else {
-                        printk(KERN_INFO
-                               "Enabling feather-trace event %d.\n", (int) id);
-                        ft_enable_event(id);
-                        ftdm->active_events++;
+                if (cmd == FTDEV_DISABLE_CMD)
+                        deactivate(&ftdm->events, id);
+                else if (activate(&ftdm->events, id) != 0) {
+                        err = -ENOMEM;
+                        goto out_unlock;
                 }
                 err += sizeof(cmd_t);
         }
@@ -271,17 +300,18 @@ struct file_operations ftdev_fops = {
 };
 
 
-void ftdev_init(struct ftdev* ftdev)
+void ftdev_init(struct ftdev* ftdev, struct module* owner)
 {
         int i;
-        ftdev->cdev.owner = THIS_MODULE;
+        cdev_init(&ftdev->cdev, &ftdev_fops);
+        ftdev->cdev.owner = owner;
         ftdev->cdev.ops = &ftdev_fops;
         ftdev->minor_cnt  = 0;
         for (i = 0; i < MAX_FTDEV_MINORS; i++) {
                 mutex_init(&ftdev->minor[i].lock);
                 ftdev->minor[i].readers = 0;
-                ftdev->minor[i].buf = NULL;
-                ftdev->minor[i].active_events = 0;
+                ftdev->minor[i].buf     = NULL;
+                ftdev->minor[i].events  = NULL;
         }
         ftdev->alloc = NULL;
         ftdev->free  = NULL;
diff --git a/litmus/trace.c b/litmus/trace.c
index 6162bb3716..2ac79a2d8b 100644
--- a/litmus/trace.c
+++ b/litmus/trace.c
@@ -79,7 +79,7 @@ static void free_timestamp_buffer(struct ftdev* ftdev, unsigned int idx)
 static int __init init_ft_overhead_trace(void)
 {
         printk("Initializing Feather-Trace overhead tracing device.\n");
-        ftdev_init(&overhead_dev);
+        ftdev_init(&overhead_dev, THIS_MODULE);
         overhead_dev.minor_cnt = 1; /* only one buffer */
         overhead_dev.alloc = alloc_timestamp_buffer;
         overhead_dev.free  = free_timestamp_buffer;