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, 12 insertions, 0 deletions

diff --git a/drivers/media/video/pvrusb2/pvrusb2-main.c b/drivers/media/video/pvrusb2/pvrusb2-main.c
index 54d9f168d7ad..332aced8a5a1 100644
--- a/drivers/media/video/pvrusb2/pvrusb2-main.c
+++ b/drivers/media/video/pvrusb2/pvrusb2-main.c
@@ -125,6 +125,12 @@ static int __init pvr_init(void)
 
         pvr2_trace(PVR2_TRACE_INIT,"pvr_init");
 
+        ret = pvr2_context_global_init();
+        if (ret != 0) {
+                pvr2_trace(PVR2_TRACE_INIT,"pvr_init failure code=%d",ret);
+                return ret;
+        }
+
 #ifdef CONFIG_VIDEO_PVRUSB2_SYSFS
         class_ptr = pvr2_sysfs_class_create();
 #endif /* CONFIG_VIDEO_PVRUSB2_SYSFS */
@@ -136,6 +142,8 @@ static int __init pvr_init(void)
         if (pvrusb2_debug) info("Debug mask is %d (0x%x)",
                                 pvrusb2_debug,pvrusb2_debug);
 
+        pvr2_trace(PVR2_TRACE_INIT,"pvr_init complete");
+
         return ret;
 }
 
@@ -148,6 +156,10 @@ static void __exit pvr_exit(void)
 #ifdef CONFIG_VIDEO_PVRUSB2_SYSFS
         pvr2_sysfs_class_destroy(class_ptr);
 #endif /* CONFIG_VIDEO_PVRUSB2_SYSFS */
+
+        pvr2_context_global_done();
+
+        pvr2_trace(PVR2_TRACE_INIT,"pvr_exit complete");
 }
 
 module_init(pvr_init);