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author | Ian Abbott | 2013-11-08 16:03:24 +0100 |
---|---|---|
committer | Greg Kroah-Hartman | 2013-11-12 01:16:43 +0100 |
commit | 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (patch) | |
tree | e76f74a1dbd8f00650298df96cc0b5679d7e5db8 /drivers | |
parent | staging: comedi: add a couple of #includes to comedidev.h (diff) | |
download | kernel-qcow2-linux-2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1.tar.gz kernel-qcow2-linux-2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1.tar.xz kernel-qcow2-linux-2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1.zip |
staging: comedi: add rw_semaphore to protect against device detachment
The 'read' and 'write' file operations on comedi devices do not use the
main mutex in the `struct comedi_device` to avoid contention with ioctls
that may take a while to complete. However, it is necessary to protect
against the device being detached while the operation is in progress.
Add member `struct rw_semaphore attach_lock` to `struct comedi_device`
for this purpose and initialize it on creation.
The actual locking and unlocking will be implemented by subsequent
patches. Tasks that are attaching or detaching comedi devices will
write-acquire the new semaphore whilst also holding the main mutex in
the `struct comedi_device`. Tasks that wish to protect against the
comedi device being detached need to acquire either the main mutex, or
read-acquire the new semaphore, or both in that order.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/staging/comedi/comedi_fops.c | 1 | ||||
-rw-r--r-- | drivers/staging/comedi/comedidev.h | 2 |
2 files changed, 3 insertions, 0 deletions
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 0d8565428abb..a1705ed0b844 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -91,6 +91,7 @@ static void comedi_device_init(struct comedi_device *dev) { spin_lock_init(&dev->spinlock); mutex_init(&dev->mutex); + init_rwsem(&dev->attach_lock); dev->minor = -1; } diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h index e2432471c390..70de3558c74e 100644 --- a/drivers/staging/comedi/comedidev.h +++ b/drivers/staging/comedi/comedidev.h @@ -22,6 +22,7 @@ #include <linux/dma-mapping.h> #include <linux/mutex.h> #include <linux/spinlock_types.h> +#include <linux/rwsem.h> #include "comedi.h" @@ -184,6 +185,7 @@ struct comedi_device { bool ioenabled:1; spinlock_t spinlock; struct mutex mutex; + struct rw_semaphore attach_lock; int n_subdevices; struct comedi_subdevice *subdevices; |