V4L/DVB (7711): pvrusb2: Fix race on module unload

The pvrusb2 driver - for basically forever - was not enforcing a
proper module tear-down.  Kernel threads are used inside the driver
and all must be gone before the module can be safely removed.  This
changeset reimplements a chunk of pvrusb2-context.c to enforce this
correctly.  Unfortunately this is not a simple fix.  The new
implementation also cuts back on kernel thread usage; instead of there
being 1 control thread per instance now it's just 1 control thread
shared by all instances.  (By dropping to a single thread then the
module exit function can block on its shutdown and the thread itself
can monitor and cleanly shut down all of the other instances first.)

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/media/video/pvrusb2/pvrusb2-context.h b/drivers/media/video/pvrusb2/pvrusb2-context.h
index 127ec53e091..6fb6ab02285 100644
--- a/drivers/media/video/pvrusb2/pvrusb2-context.h
+++ b/drivers/media/video/pvrusb2/pvrusb2-context.h
@@ -40,14 +40,17 @@ struct pvr2_context_stream {
 struct pvr2_context {
 	struct pvr2_channel *mc_first;
 	struct pvr2_channel *mc_last;
+	struct pvr2_context *exist_next;
+	struct pvr2_context *exist_prev;
+	struct pvr2_context *notify_next;
+	struct pvr2_context *notify_prev;
 	struct pvr2_hdw *hdw;
 	struct pvr2_context_stream video_stream;
 	struct mutex mutex;
 	int notify_flag;
+	int initialized_flag;
 	int disconnect_flag;
 
-	wait_queue_head_t wait_data;
-
 	/* Called after pvr2_context initialization is complete */
 	void (*setup_func)(struct pvr2_context *);
 
@@ -74,6 +77,8 @@ int pvr2_channel_claim_stream(struct pvr2_channel *,
 struct pvr2_ioread *pvr2_channel_create_mpeg_stream(
 	struct pvr2_context_stream *);
 
+int pvr2_context_global_init(void);
+void pvr2_context_global_done(void);
 
 #endif /* __PVRUSB2_CONTEXT_H */
 /*