linux-kernel - [PATCH 1/2] staging: comedi: das16: deschedule timer routine on detach

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Message-Id: <1414604112-4362-2-git-send-email-abbotti@mev.co.uk>
Date:	Wed, 29 Oct 2014 17:35:11 +0000
From:	Ian Abbott <abbotti@....co.uk>
To:	<driverdev-devel@...uxdriverproject.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ian Abbott <abbotti@....co.uk>,
	H Hartley Sweeten <hartleys@...ionengravers.com>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] staging: comedi: das16: deschedule timer routine on detach

The "das16" driver optionally uses a kernel timer and a DMA channel to
support asynchronous data acquisition, but currently never calls
`del_timer_sync()`.  There is some possibility the timer routine could
still be scheduled to run when the comedi "detach" handler is run to
clean up the device and cause a certain amount of havoc.  Avoid that by
calling `del_time_sync()` in the comedi "detach" handler
`das16_detach()` if the timer was initialized by the "attach" handler
`das16_attach()`.  Use the timer's `data` member to tell whether it was
initialized or not.

Signed-off-by: Ian Abbott <abbotti@....co.uk>
---
 drivers/staging/comedi/drivers/das16.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/comedi/drivers/das16.c b/drivers/staging/comedi/drivers/das16.c
index 5d47d0a..51c4a58 100644
--- a/drivers/staging/comedi/drivers/das16.c
+++ b/drivers/staging/comedi/drivers/das16.c
@@ -1226,6 +1226,8 @@ static void das16_detach(struct comedi_device *dev)
 	int i;

 	if (devpriv) {
+		if (devpriv->timer.data)
+			del_timer_sync(&devpriv->timer);
 		if (dev->iobase)
 			das16_reset(dev);

-- 
2.1.1

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