From bf11c134246e8f3cfa2582a3d2af84ed7dfd59b6 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Fri, 8 Nov 2013 15:03:25 +0000 Subject: [PATCH] staging: comedi: use attach_lock semaphore during attach and detach Acquire the `attach_lock` semaphore in the `struct comedi_device` while modifying the `attached` flag. This is a "write" acquire. Note that the main mutex in the `struct comedi_device` is also held at this time. Tasks wishing to check the device is attached will need to either acquire the main mutex, or "read" acquire the `attach_lock` semaphore, or both in that order. Signed-off-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c index 8f02bf6..c398422 100644 --- a/drivers/staging/comedi/drivers.c +++ b/drivers/staging/comedi/drivers.c @@ -133,10 +133,12 @@ static void cleanup_device(struct comedi_device *dev) void comedi_device_detach(struct comedi_device *dev) { + down_write(&dev->attach_lock); dev->attached = false; if (dev->driver) dev->driver->detach(dev); cleanup_device(dev); + up_write(&dev->attach_lock); } static int poll_invalid(struct comedi_device *dev, struct comedi_subdevice *s) @@ -355,8 +357,9 @@ static int comedi_device_postconfig(struct comedi_device *dev) ret = __comedi_device_postconfig(dev); if (ret < 0) return ret; - smp_wmb(); + down_write(&dev->attach_lock); dev->attached = true; + up_write(&dev->attach_lock); return 0; } -- 2.7.4