[PATCH 1/2] [RFC PATCH v6] dmabuf-sync: Add a buffer synchronization framework
Inki Dae
inki.dae at samsung.com
Wed Aug 21 01:40:05 PDT 2013
Thanks for the review,
Inki Dae
> -----Original Message-----
> From: linux-fbdev-owner at vger.kernel.org [mailto:linux-fbdev-
> owner at vger.kernel.org] On Behalf Of Konrad Rzeszutek Wilk
> Sent: Wednesday, August 21, 2013 4:22 AM
> To: Inki Dae
> Cc: dri-devel at lists.freedesktop.org; linux-fbdev at vger.kernel.org; linux-
> arm-kernel at lists.infradead.org; linux-media at vger.kernel.org; linaro-
> kernel at lists.linaro.org; kyungmin.park at samsung.com;
> myungjoo.ham at samsung.com
> Subject: Re: [PATCH 1/2] [RFC PATCH v6] dmabuf-sync: Add a buffer
> synchronization framework
>
> On Tue, Aug 13, 2013 at 06:19:35PM +0900, Inki Dae wrote:
> > This patch adds a buffer synchronization framework based on DMA BUF[1]
> > and and based on ww-mutexes[2] for lock mechanism.
> >
> > The purpose of this framework is to provide not only buffer access
> control
> > to CPU and DMA but also easy-to-use interfaces for device drivers and
> > user application. This framework can be used for all dma devices using
> > system memory as dma buffer, especially for most ARM based SoCs.
> >
> > Changelog v6:
> > - Fix sync lock to multiple reads.
> > - Add select system call support.
> > . Wake up poll_wait when a dmabuf is unlocked.
> > - Remove unnecessary the use of mutex lock.
> > - Add private backend ops callbacks.
> > . This ops has one callback for device drivers to clean up their
> > sync object resource when the sync object is freed. For this,
> > device drivers should implement the free callback properly.
> > - Update document file.
> >
> > Changelog v5:
> > - Rmove a dependence on reservation_object: the reservation_object is
> used
> > to hook up to ttm and dma-buf for easy sharing of reservations across
> > devices. However, the dmabuf sync can be used for all dma devices;
> v4l2
> > and drm based drivers, so doesn't need the reservation_object anymore.
> > With regared to this, it adds 'void *sync' to dma_buf structure.
> > - All patches are rebased on mainline, Linux v3.10.
> >
> > Changelog v4:
> > - Add user side interface for buffer synchronization mechanism and
> update
> > descriptions related to the user side interface.
> >
> > Changelog v3:
> > - remove cache operation relevant codes and update document file.
> >
> > Changelog v2:
> > - use atomic_add_unless to avoid potential bug.
> > - add a macro for checking valid access type.
> > - code clean.
> >
> > The mechanism of this framework has the following steps,
> > 1. Register dmabufs to a sync object - A task gets a new sync object
> and
> > can add one or more dmabufs that the task wants to access.
> > This registering should be performed when a device context or an
> event
> > context such as a page flip event is created or before CPU accesses
a
> shared
> > buffer.
> >
> > dma_buf_sync_get(a sync object, a dmabuf);
> >
> > 2. Lock a sync object - A task tries to lock all dmabufs added in
its
> own
> > sync object. Basically, the lock mechanism uses ww-mutex[1] to avoid
> dead
> > lock issue and for race condition between CPU and CPU, CPU and DMA,
> and DMA
> > and DMA. Taking a lock means that others cannot access all locked
> dmabufs
> > until the task that locked the corresponding dmabufs, unlocks all
the
> locked
> > dmabufs.
> > This locking should be performed before DMA or CPU accesses these
> dmabufs.
> >
> > dma_buf_sync_lock(a sync object);
> >
> > 3. Unlock a sync object - The task unlocks all dmabufs added in its
> own sync
> > object. The unlock means that the DMA or CPU accesses to the dmabufs
> have
> > been completed so that others may access them.
> > This unlocking should be performed after DMA or CPU has completed
> accesses
> > to the dmabufs.
> >
> > dma_buf_sync_unlock(a sync object);
> >
> > 4. Unregister one or all dmabufs from a sync object - A task
> unregisters
> > the given dmabufs from the sync object. This means that the task
> dosen't
> > want to lock the dmabufs.
> > The unregistering should be performed after DMA or CPU has completed
> > accesses to the dmabufs or when dma_buf_sync_lock() is failed.
> >
> > dma_buf_sync_put(a sync object, a dmabuf);
> > dma_buf_sync_put_all(a sync object);
> >
> > The described steps may be summarized as:
> > get -> lock -> CPU or DMA access to a buffer/s -> unlock -> put
> >
> > This framework includes the following two features.
> > 1. read (shared) and write (exclusive) locks - A task is required to
> declare
> > the access type when the task tries to register a dmabuf;
> > READ, WRITE, READ DMA, or WRITE DMA.
> >
> > The below is example codes,
> > struct dmabuf_sync *sync;
> >
> > sync = dmabuf_sync_init(...);
> > ...
> >
> > dmabuf_sync_get(sync, dmabuf, DMA_BUF_ACCESS_R);
> > ...
> >
> > And the below can be used as access types:
> > DMA_BUF_ACCESS_R - CPU will access a buffer for read.
> > DMA_BUF_ACCESS_W - CPU will access a buffer for read or
> write.
> > DMA_BUF_ACCESS_DMA_R - DMA will access a buffer for read
> > DMA_BUF_ACCESS_DMA_W - DMA will access a buffer for read or
> > write.
> >
> > 2. Mandatory resource releasing - a task cannot hold a lock
> indefinitely.
> > A task may never try to unlock a buffer after taking a lock to the
> buffer.
> > In this case, a timer handler to the corresponding sync object is
> called
> > in five (default) seconds and then the timed-out buffer is unlocked
> by work
> > queue handler to avoid lockups and to enforce resources of the
buffer.
> >
> > The below is how to use interfaces for device driver:
> > 1. Allocate and Initialize a sync object:
> > static void xxx_dmabuf_sync_free(void *priv)
> > {
> > struct xxx_context *ctx = priv;
> >
> > if (!ctx)
> > return;
> >
> > ctx->sync = NULL;
> > }
> > ...
> >
> > static struct dmabuf_sync_priv_ops driver_specific_ops = {
> > .free = xxx_dmabuf_sync_free,
> > };
> > ...
> >
> > struct dmabuf_sync *sync;
> >
> > sync = dmabuf_sync_init("test sync", &driver_specific_ops,
> ctx);
> > ...
> >
> > 2. Add a dmabuf to the sync object when setting up dma buffer
> relevant
> > registers:
> > dmabuf_sync_get(sync, dmabuf, DMA_BUF_ACCESS_READ);
> > ...
> >
> > 3. Lock all dmabufs of the sync object before DMA or CPU accesses
> > the dmabufs:
> > dmabuf_sync_lock(sync);
> > ...
> >
> > 4. Now CPU or DMA can access all dmabufs locked in step 3.
> >
> > 5. Unlock all dmabufs added in a sync object after DMA or CPU
> access
> > to these dmabufs is completed:
> > dmabuf_sync_unlock(sync);
> >
> > And call the following functions to release all resources,
> > dmabuf_sync_put_all(sync);
> > dmabuf_sync_fini(sync);
> >
> > You can refer to actual example codes:
> > "drm/exynos: add dmabuf sync support for g2d driver" and
> > "drm/exynos: add dmabuf sync support for kms framework" from
> > https://git.kernel.org/cgit/linux/kernel/git/daeinki/
> > drm-exynos.git/log/?h=dmabuf-sync
> >
> > And this framework includes fcntl system call[3] as interfaces exported
> > to user. As you know, user sees a buffer object as a dma-buf file
> descriptor.
> > So fcntl() call with the file descriptor means to lock some buffer
> region being
> > managed by the dma-buf object.
> >
> > The below is how to use interfaces for user application:
> >
> > fcntl system call:
> >
> > struct flock filelock;
> >
> > 1. Lock a dma buf:
> > filelock.l_type = F_WRLCK or F_RDLCK;
> >
> > /* lock entire region to the dma buf. */
> > filelock.lwhence = SEEK_CUR;
> > filelock.l_start = 0;
> > filelock.l_len = 0;
> >
> > fcntl(dmabuf fd, F_SETLKW or F_SETLK, &filelock);
> > ...
> > CPU access to the dma buf
> >
> > 2. Unlock a dma buf:
> > filelock.l_type = F_UNLCK;
> >
> > fcntl(dmabuf fd, F_SETLKW or F_SETLK, &filelock);
> >
> > close(dmabuf fd) call would also unlock the dma buf. And for
> more
> > detail, please refer to [3]
> >
> > select system call:
> >
> > fd_set wdfs or rdfs;
> >
> > FD_ZERO(&wdfs or &rdfs);
> > FD_SET(fd, &wdfs or &rdfs);
> >
> > select(fd + 1, &rdfs, NULL, NULL, NULL);
> > or
> > select(fd + 1, NULL, &wdfs, NULL, NULL);
> >
> > Every time select system call is called, a caller will wait for
> > the completion of DMA or CPU access to a shared buffer if there
> > is someone accessing the shared buffer; locked the shared buffer.
> > However, if no anyone then select system call will be returned
> > at once.
> >
> > References:
> > [1] http://lwn.net/Articles/470339/
> > [2] https://patchwork.kernel.org/patch/2625361/
> > [3] http://linux.die.net/man/2/fcntl
> >
> > Signed-off-by: Inki Dae <inki.dae at samsung.com>
> > Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
> > ---
> > Documentation/dma-buf-sync.txt | 285 +++++++++++++++++
> > drivers/base/Kconfig | 7 +
> > drivers/base/Makefile | 1 +
> > drivers/base/dma-buf.c | 4 +
> > drivers/base/dmabuf-sync.c | 678
> ++++++++++++++++++++++++++++++++++++++++
> > include/linux/dma-buf.h | 16 +
> > include/linux/dmabuf-sync.h | 190 +++++++++++
> > 7 files changed, 1181 insertions(+), 0 deletions(-)
> > create mode 100644 Documentation/dma-buf-sync.txt
> > create mode 100644 drivers/base/dmabuf-sync.c
> > create mode 100644 include/linux/dmabuf-sync.h
> >
> > diff --git a/Documentation/dma-buf-sync.txt b/Documentation/dma-buf-
> sync.txt
> > new file mode 100644
> > index 0000000..8023d06
> > --- /dev/null
> > +++ b/Documentation/dma-buf-sync.txt
> > @@ -0,0 +1,285 @@
> > + DMA Buffer Synchronization Framework
> > + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +
> > + Inki Dae
> > + <inki dot dae at samsung dot com>
> > + <daeinki at gmail dot com>
> > +
> > +This document is a guide for device-driver writers describing the DMA
> buffer
> > +synchronization API. This document also describes how to use the API to
> > +use buffer synchronization mechanism between DMA and DMA, CPU and DMA,
> and
> > +CPU and CPU.
> > +
> > +The DMA Buffer synchronization API provides buffer synchronization
> mechanism;
> > +i.e., buffer access control to CPU and DMA, and easy-to-use interfaces
> for
> > +device drivers and user application. And this API can be used for all
> dma
> > +devices using system memory as dma buffer, especially for most ARM
> based SoCs.
> > +
> > +
> > +Motivation
> > +----------
> > +
> > +Buffer synchronization issue between DMA and DMA:
> > + Sharing a buffer, a device cannot be aware of when the other device
> > + will access the shared buffer: a device may access a buffer
> containing
> > + wrong data if the device accesses the shared buffer while another
> > + device is still accessing the shared buffer.
> > + Therefore, a user process should have waited for the completion of
> DMA
> > + access by another device before a device tries to access the shared
> > + buffer.
> > +
> > +Buffer synchronization issue between CPU and DMA:
> > + A user process should consider that when having to send a buffer,
> filled
> > + by CPU, to a device driver for the device driver to access the
> buffer as
> > + a input buffer while CPU and DMA are sharing the buffer.
> > + This means that the user process needs to understand how the device
> > + driver is worked. Hence, the conventional mechanism not only makes
> > + user application complicated but also incurs performance overhead.
> > +
> > +Buffer synchronization issue between CPU and CPU:
> > + In case that two processes share one buffer; shared with DMA also,
> > + they may need some mechanism to allow process B to access the
> shared
> > + buffer after the completion of CPU access by process A.
> > + Therefore, process B should have waited for the completion of CPU
> access
> > + by process A using the mechanism before trying to access the shared
> > + buffer.
> > +
> > +What is the best way to solve these buffer synchronization issues?
> > + We may need a common object that a device driver and a user process
> > + notify the common object of when they try to access a shared buffer.
> > + That way we could decide when we have to allow or not to allow for
> CPU
> > + or DMA to access the shared buffer through the common object.
> > + If so, what could become the common object? Right, that's a dma-
> buf[1].
> > + Now we have already been using the dma-buf to share one buffer with
> > + other drivers.
> > +
> > +
> > +Basic concept
> > +-------------
> > +
> > +The mechanism of this framework has the following steps,
> > + 1. Register dmabufs to a sync object - A task gets a new sync
object
> and
> > + can add one or more dmabufs that the task wants to access.
> > + This registering should be performed when a device context or an
> event
> > + context such as a page flip event is created or before CPU accesses
> a shared
> > + buffer.
> > +
> > + dma_buf_sync_get(a sync object, a dmabuf);
> > +
> > + 2. Lock a sync object - A task tries to lock all dmabufs added in
> its own
> > + sync object. Basically, the lock mechanism uses ww-mutexes[2] to
> avoid dead
> > + lock issue and for race condition between CPU and CPU, CPU and DMA,
> and DMA
> > + and DMA. Taking a lock means that others cannot access all locked
> dmabufs
> > + until the task that locked the corresponding dmabufs, unlocks all
> the locked
> > + dmabufs.
> > + This locking should be performed before DMA or CPU accesses these
> dmabufs.
> > +
> > + dma_buf_sync_lock(a sync object);
> > +
> > + 3. Unlock a sync object - The task unlocks all dmabufs added in its
> own sync
> > + object. The unlock means that the DMA or CPU accesses to the
dmabufs
> have
> > + been completed so that others may access them.
> > + This unlocking should be performed after DMA or CPU has completed
> accesses
> > + to the dmabufs.
> > +
> > + dma_buf_sync_unlock(a sync object);
> > +
> > + 4. Unregister one or all dmabufs from a sync object - A task
> unregisters
> > + the given dmabufs from the sync object. This means that the task
> dosen't
> > + want to lock the dmabufs.
> > + The unregistering should be performed after DMA or CPU has
completed
> > + accesses to the dmabufs or when dma_buf_sync_lock() is failed.
> > +
> > + dma_buf_sync_put(a sync object, a dmabuf);
> > + dma_buf_sync_put_all(a sync object);
> > +
> > + The described steps may be summarized as:
> > + get -> lock -> CPU or DMA access to a buffer/s -> unlock -> put
> > +
> > +This framework includes the following two features.
> > + 1. read (shared) and write (exclusive) locks - A task is required
to
> declare
> > + the access type when the task tries to register a dmabuf;
> > + READ, WRITE, READ DMA, or WRITE DMA.
> > +
> > + The below is example codes,
> > + struct dmabuf_sync *sync;
> > +
> > + sync = dmabuf_sync_init(NULL, "test sync");
> > +
> > + dmabuf_sync_get(sync, dmabuf, DMA_BUF_ACCESS_R);
> > + ...
> > +
> > + 2. Mandatory resource releasing - a task cannot hold a lock
> indefinitely.
> > + A task may never try to unlock a buffer after taking a lock to the
> buffer.
> > + In this case, a timer handler to the corresponding sync object is
> called
> > + in five (default) seconds and then the timed-out buffer is unlocked
> by work
> > + queue handler to avoid lockups and to enforce resources of the
> buffer.
> > +
> > +
> > +Access types
> > +------------
> > +
> > +DMA_BUF_ACCESS_R - CPU will access a buffer for read.
> > +DMA_BUF_ACCESS_W - CPU will access a buffer for read or write.
> > +DMA_BUF_ACCESS_DMA_R - DMA will access a buffer for read
> > +DMA_BUF_ACCESS_DMA_W - DMA will access a buffer for read or write.
> > +
> > +
> > +Generic user interfaces
> > +-----------------------
> > +
> > +And this framework includes fcntl system call[3] as interfaces exported
> > +to user. As you know, user sees a buffer object as a dma-buf file
> descriptor.
> > +So fcntl() call with the file descriptor means to lock some buffer
> region being
> > +managed by the dma-buf object.
> > +
> > +
> > +API set
> > +-------
> > +
> > +bool is_dmabuf_sync_supported(void)
> > + - Check if dmabuf sync is supported or not.
> > +
> > +struct dmabuf_sync *dmabuf_sync_init(const char *name,
> > + struct dmabuf_sync_priv_ops *ops,
> > + void priv*)
> > + - Allocate and initialize a new sync object. The caller can get a
> new
> > + sync object for buffer synchronization. ops is used for device
> driver
> > + to clean up its own sync object. For this, each device driver
> should
> > + implement a free callback. priv is used for device driver to get
> its
> > + device context when free callback is called.
> > +
> > +void dmabuf_sync_fini(struct dmabuf_sync *sync)
> > + - Release all resources to the sync object.
> > +
> > +int dmabuf_sync_get(struct dmabuf_sync *sync, void *sync_buf,
> > + unsigned int type)
> > + - Get dmabuf sync object. Internally, this function allocates
> > + a dmabuf_sync object and adds a given dmabuf to it, and also takes
> > + a reference to the dmabuf. The caller can tie up multiple dmabufs
> > + into one sync object by calling this function several times.
> > +
> > +void dmabuf_sync_put(struct dmabuf_sync *sync, struct dma_buf *dmabuf)
> > + - Put dmabuf sync object to a given dmabuf. Internally, this
> function
> > + removes a given dmabuf from a sync object and remove the sync
> object.
> > + At this time, the dmabuf is putted.
> > +
> > +void dmabuf_sync_put_all(struct dmabuf_sync *sync)
> > + - Put dmabuf sync object to dmabufs. Internally, this function
> removes
> > + all dmabufs from a sync object and remove the sync object.
> > + At this time, all dmabufs are putted.
> > +
> > +int dmabuf_sync_lock(struct dmabuf_sync *sync)
> > + - Lock all dmabufs added in a sync object. The caller should call
> this
> > + function prior to CPU or DMA access to the dmabufs so that others
> can
> > + not access the dmabufs. Internally, this function avoids dead lock
> > + issue with ww-mutexes.
> > +
> > +int dmabuf_sync_single_lock(struct dma_buf *dmabuf)
> > + - Lock a dmabuf. The caller should call this
> > + function prior to CPU or DMA access to the dmabuf so that others
> can
> > + not access the dmabuf.
> > +
> > +int dmabuf_sync_unlock(struct dmabuf_sync *sync)
> > + - Unlock all dmabufs added in a sync object. The caller should call
> > + this function after CPU or DMA access to the dmabufs is completed
> so
> > + that others can access the dmabufs.
> > +
> > +void dmabuf_sync_single_unlock(struct dma_buf *dmabuf)
> > + - Unlock a dmabuf. The caller should call this function after CPU
> or
> > + DMA access to the dmabuf is completed so that others can access
> > + the dmabuf.
> > +
> > +
> > +Tutorial for device driver
> > +--------------------------
> > +
> > +1. Allocate and Initialize a sync object:
> > + static void xxx_dmabuf_sync_free(void *priv)
> > + {
> > + struct xxx_context *ctx = priv;
> > +
> > + if (!ctx)
> > + return;
> > +
> > + ctx->sync = NULL;
> > + }
> > + ...
> > +
> > + static struct dmabuf_sync_priv_ops driver_specific_ops = {
> > + .free = xxx_dmabuf_sync_free,
> > + };
> > + ...
> > +
> > + struct dmabuf_sync *sync;
> > +
> > + sync = dmabuf_sync_init("test sync", &driver_specific_ops, ctx);
> > + ...
> > +
> > +2. Add a dmabuf to the sync object when setting up dma buffer relevant
> registers:
> > + dmabuf_sync_get(sync, dmabuf, DMA_BUF_ACCESS_READ);
> > + ...
> > +
> > +3. Lock all dmabufs of the sync object before DMA or CPU accesses the
> dmabufs:
> > + dmabuf_sync_lock(sync);
> > + ...
> > +
> > +4. Now CPU or DMA can access all dmabufs locked in step 3.
> > +
> > +5. Unlock all dmabufs added in a sync object after DMA or CPU access to
> these
> > + dmabufs is completed:
> > + dmabuf_sync_unlock(sync);
> > +
> > + And call the following functions to release all resources,
> > + dmabuf_sync_put_all(sync);
> > + dmabuf_sync_fini(sync);
> > +
> > +
> > +Tutorial for user application
> > +-----------------------------
> > +fcntl system call:
> > +
> > + struct flock filelock;
> > +
> > +1. Lock a dma buf:
> > + filelock.l_type = F_WRLCK or F_RDLCK;
> > +
> > + /* lock entire region to the dma buf. */
> > + filelock.lwhence = SEEK_CUR;
> > + filelock.l_start = 0;
> > + filelock.l_len = 0;
> > +
> > + fcntl(dmabuf fd, F_SETLKW or F_SETLK, &filelock);
> > + ...
> > + CPU access to the dma buf
> > +
> > +2. Unlock a dma buf:
> > + filelock.l_type = F_UNLCK;
> > +
> > + fcntl(dmabuf fd, F_SETLKW or F_SETLK, &filelock);
> > +
> > + close(dmabuf fd) call would also unlock the dma buf. And for more
> > + detail, please refer to [3]
> > +
> > +
> > +select system call:
> > +
> > + fd_set wdfs or rdfs;
> > +
> > + FD_ZERO(&wdfs or &rdfs);
> > + FD_SET(fd, &wdfs or &rdfs);
> > +
> > + select(fd + 1, &rdfs, NULL, NULL, NULL);
> > + or
> > + select(fd + 1, NULL, &wdfs, NULL, NULL);
> > +
> > + Every time select system call is called, a caller will wait for
> > + the completion of DMA or CPU access to a shared buffer if there is
> > + someone accessing the shared buffer; locked the shared buffer.
> > + However, if no anyone then select system call will be returned
> > + at once.
> > +
> > +References:
> > +[1] http://lwn.net/Articles/470339/
> > +[2] https://patchwork.kernel.org/patch/2625361/
> > +[3] http://linux.die.net/man/2/fcntl
> > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> > index 5daa259..35e1518 100644
> > --- a/drivers/base/Kconfig
> > +++ b/drivers/base/Kconfig
> > @@ -200,6 +200,13 @@ config DMA_SHARED_BUFFER
> > APIs extension; the file's descriptor can then be passed on to
> other
> > driver.
> >
> > +config DMABUF_SYNC
> > + bool "DMABUF Synchronization Framework"
> > + depends on DMA_SHARED_BUFFER
> > + help
> > + This option enables dmabuf sync framework for buffer
> synchronization between
> > + DMA and DMA, CPU and DMA, and CPU and CPU.
> > +
> > config CMA
> > bool "Contiguous Memory Allocator"
> > depends on HAVE_DMA_CONTIGUOUS && HAVE_MEMBLOCK
> > diff --git a/drivers/base/Makefile b/drivers/base/Makefile
> > index 48029aa..e06a5d7 100644
> > --- a/drivers/base/Makefile
> > +++ b/drivers/base/Makefile
> > @@ -11,6 +11,7 @@ obj-y += power/
> > obj-$(CONFIG_HAS_DMA) += dma-mapping.o
> > obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
> > obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o reservation.o
> > +obj-$(CONFIG_DMABUF_SYNC) += dmabuf-sync.o
> > obj-$(CONFIG_ISA) += isa.o
> > obj-$(CONFIG_FW_LOADER) += firmware_class.o
> > obj-$(CONFIG_NUMA) += node.o
> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> > index 6687ba7..4aca57a 100644
> > --- a/drivers/base/dma-buf.c
> > +++ b/drivers/base/dma-buf.c
> > @@ -29,6 +29,7 @@
> > #include <linux/export.h>
> > #include <linux/debugfs.h>
> > #include <linux/seq_file.h>
> > +#include <linux/dmabuf-sync.h>
> >
> > static inline int is_dma_buf_file(struct file *);
> >
> > @@ -56,6 +57,8 @@ static int dma_buf_release(struct inode *inode, struct
> file *file)
> > list_del(&dmabuf->list_node);
> > mutex_unlock(&db_list.lock);
> >
> > + dmabuf_sync_reservation_fini(dmabuf);
> > +
> > kfree(dmabuf);
> > return 0;
> > }
> > @@ -134,6 +137,7 @@ struct dma_buf *dma_buf_export_named(void *priv,
> const struct dma_buf_ops *ops,
> >
> > file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
> >
> > + dmabuf_sync_reservation_init(dmabuf);
> > dmabuf->file = file;
> >
> > mutex_init(&dmabuf->lock);
> > diff --git a/drivers/base/dmabuf-sync.c b/drivers/base/dmabuf-sync.c
> > new file mode 100644
> > index 0000000..fbe711c
> > --- /dev/null
> > +++ b/drivers/base/dmabuf-sync.c
> > @@ -0,0 +1,678 @@
> > +/*
> > + * Copyright (C) 2013 Samsung Electronics Co.Ltd
> > + * Authors:
> > + * Inki Dae <inki.dae at samsung.com>
> > + *
> > + * This program is free software; you can redistribute it and/or
> modify it
> > + * under the terms of the GNU General Public License as published by
> the
> > + * Free Software Foundation; either version 2 of the License, or (at
> your
> > + * option) any later version.
> > + *
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/debugfs.h>
> > +#include <linux/uaccess.h>
> > +
> > +#include <linux/dmabuf-sync.h>
> > +
> > +#define MAX_SYNC_TIMEOUT 5 /* Second. */
> > +
> > +int dmabuf_sync_enabled = 1;
> > +
> > +MODULE_PARM_DESC(enabled, "Check if dmabuf sync is supported or not");
> > +module_param_named(enabled, dmabuf_sync_enabled, int, 0444);
> > +
> > +DEFINE_WW_CLASS(dmabuf_sync_ww_class);
> > +EXPORT_SYMBOL(dmabuf_sync_ww_class);
> > +
> > +static void dmabuf_sync_timeout_worker(struct work_struct *work)
> > +{
> > + struct dmabuf_sync *sync = container_of(work, struct dmabuf_sync,
> work);
> > + struct dmabuf_sync_object *sobj;
> > +
> > + mutex_lock(&sync->lock);
> > +
> > + list_for_each_entry(sobj, &sync->syncs, head) {
>
> You are using the 'sobj->robj' quite a lot. Why not just use a temp
> structure:
>
> struct dmabuf_sync_reservation *rsvp = sobj->robj;
>
> and use that in this function. It would make it easier to read I think.
Ok, will use the temp structure.
>
>
> > + BUG_ON(!sobj->robj);
> > +
> > + mutex_lock(&sobj->robj->lock);
> > +
> > + printk(KERN_WARNING "%s: timeout = 0x%x [type = %d:%d, " \
> > + "refcnt = %d, locked = %d]\n",
> > + sync->name, (u32)sobj->dmabuf,
> > + sobj->robj->accessed_type,
> > + sobj->access_type,
> > +
atomic_read(&sobj->robj->shared_cnt),
> > + sobj->robj->locked);
>
> pr_warn_ratelimited?
Will use pr_warn because the timeout worker handler isn't called so
frequently so the printk storm wouldn't be caused
>
> > +
> > + /* unlock only valid sync object. */
> > + if (!sobj->robj->locked) {
> > + mutex_unlock(&sobj->robj->lock);
> > + continue;
> > + }
> > +
> > + if (sobj->robj->polled) {
> > + sobj->robj->poll_event = true;
> > + sobj->robj->polled = false;
> > + wake_up_interruptible(&sobj->robj->poll_wait);
> > + }
> > +
> > + if (atomic_add_unless(&sobj->robj->shared_cnt, -1, 1)) {
> > + mutex_unlock(&sobj->robj->lock);
> > + continue;
> > + }
> > +
> > + mutex_unlock(&sobj->robj->lock);
> > +
> > + ww_mutex_unlock(&sobj->robj->sync_lock);
> > +
> > + mutex_lock(&sobj->robj->lock);
> > + sobj->robj->locked = false;
> > +
> > + if (sobj->access_type & DMA_BUF_ACCESS_R)
> > + printk(KERN_WARNING "%s: r-unlocked = 0x%x\n",
> > + sync->name, (u32)sobj->dmabuf);
> > + else
> > + printk(KERN_WARNING "%s: w-unlocked = 0x%x\n",
> > + sync->name, (u32)sobj->dmabuf);
>
> How about using 'pr_warn'? And in it have:
Ok, will use it.
>
> sobj->access_type & DMA_BUF_ACCESS_R ? "r-" : "w-",
>
> and just have one printk.
>
> Why the (u32) casting? Don't you want %p ?
Right, I should had used %p instead. Will remove the casting and use %p
instead.
>
> > +
> > + mutex_unlock(&sobj->robj->lock);
> > + }
> > +
> > + sync->status = 0;
> > + mutex_unlock(&sync->lock);
> > +
> > + dmabuf_sync_put_all(sync);
> > + dmabuf_sync_fini(sync);
> > +}
> > +
> > +static void dmabuf_sync_lock_timeout(unsigned long arg)
> > +{
> > + struct dmabuf_sync *sync = (struct dmabuf_sync *)arg;
> > +
> > + schedule_work(&sync->work);
> > +}
> > +
> > +static int dmabuf_sync_lock_objs(struct dmabuf_sync *sync,
> > + struct ww_acquire_ctx *ctx)
> > +{
> > + struct dmabuf_sync_object *contended_sobj = NULL;
> > + struct dmabuf_sync_object *res_sobj = NULL;
> > + struct dmabuf_sync_object *sobj = NULL;
> > + int ret;
> > +
> > + if (ctx)
> > + ww_acquire_init(ctx, &dmabuf_sync_ww_class);
> > +
> > +retry:
> > + list_for_each_entry(sobj, &sync->syncs, head) {
> > + if (WARN_ON(!sobj->robj))
> > + continue;
> > +
> > + mutex_lock(&sobj->robj->lock);
> > +
> > + /* Don't lock in case of read and read. */
> > + if (sobj->robj->accessed_type & DMA_BUF_ACCESS_R &&
> > + sobj->access_type & DMA_BUF_ACCESS_R) {
> > + atomic_inc(&sobj->robj->shared_cnt);
> > + mutex_unlock(&sobj->robj->lock);
> > + continue;
> > + }
> > +
> > + if (sobj == res_sobj) {
> > + res_sobj = NULL;
> > + mutex_unlock(&sobj->robj->lock);
> > + continue;
> > + }
> > +
> > + mutex_unlock(&sobj->robj->lock);
> > +
> > + ret = ww_mutex_lock(&sobj->robj->sync_lock, ctx);
> > + if (ret < 0) {
> > + contended_sobj = sobj;
> > +
> > + if (ret == -EDEADLK)
> > + printk(KERN_WARNING"%s: deadlock = 0x%x\n",
> > + sync->name, (u32)sobj->dmabuf);
>
> Again, why (u32) and not %p?
>
> > + goto err;
>
> This looks odd. You jump to err, which jumps back to 'retry'. Won't this
> cause an infinite loop? Perhaps you need to add a retry counter to only
> do this up to five times or so and then give up?
It jumps to err only if ww_mutex_lock returns -EDEADLK. This means that the
lock trying to a given sync object caused dead lock. So all robjs already
locked should be unlocked, and retried to take lock again going to err. So I
think the infinite loop isn't caused.
>
> > + }
> > +
> > + mutex_lock(&sobj->robj->lock);
> > + sobj->robj->locked = true;
> > +
> > + mutex_unlock(&sobj->robj->lock);
> > + }
> > +
> > + if (ctx)
> > + ww_acquire_done(ctx);
> > +
> > + init_timer(&sync->timer);
> > +
> > + sync->timer.data = (unsigned long)sync;
> > + sync->timer.function = dmabuf_sync_lock_timeout;
> > + sync->timer.expires = jiffies + (HZ * MAX_SYNC_TIMEOUT);
> > +
> > + add_timer(&sync->timer);
> > +
> > + return 0;
> > +
> > +err:
> > + list_for_each_entry_continue_reverse(sobj, &sync->syncs, head) {
> > + mutex_lock(&sobj->robj->lock);
> > +
> > + /* Don't need to unlock in case of read and read. */
> > + if (atomic_add_unless(&sobj->robj->shared_cnt, -1, 1)) {
> > + mutex_unlock(&sobj->robj->lock);
> > + continue;
> > + }
> > +
> > + ww_mutex_unlock(&sobj->robj->sync_lock);
> > + sobj->robj->locked = false;
> > +
> > + mutex_unlock(&sobj->robj->lock);
> > + }
> > +
> > + if (res_sobj) {
> > + mutex_lock(&res_sobj->robj->lock);
> > +
> > + if (!atomic_add_unless(&res_sobj->robj->shared_cnt, -1, 1))
> {
> > + ww_mutex_unlock(&res_sobj->robj->sync_lock);
> > + res_sobj->robj->locked = false;
> > + }
> > +
> > + mutex_unlock(&res_sobj->robj->lock);
> > + }
> > +
> > + if (ret == -EDEADLK) {
> > + ww_mutex_lock_slow(&contended_sobj->robj->sync_lock, ctx);
> > + res_sobj = contended_sobj;
> > +
> > + goto retry;
> > + }
> > +
> > + if (ctx)
> > + ww_acquire_fini(ctx);
> > +
> > + return ret;
> > +}
> > +
> > +static void dmabuf_sync_unlock_objs(struct dmabuf_sync *sync,
> > + struct ww_acquire_ctx *ctx)
> > +{
> > + struct dmabuf_sync_object *sobj;
> > +
> > + if (list_empty(&sync->syncs))
> > + return;
> > +
> > + mutex_lock(&sync->lock);
> > +
> > + list_for_each_entry(sobj, &sync->syncs, head) {
> > + mutex_lock(&sobj->robj->lock);
> > +
> > + if (sobj->robj->polled) {
> > + sobj->robj->poll_event = true;
> > + sobj->robj->polled = false;
> > + wake_up_interruptible(&sobj->robj->poll_wait);
> > + }
> > +
> > + if (atomic_add_unless(&sobj->robj->shared_cnt, -1, 1)) {
> > + mutex_unlock(&sobj->robj->lock);
> > + continue;
> > + }
> > +
> > + mutex_unlock(&sobj->robj->lock);
> > +
> > + ww_mutex_unlock(&sobj->robj->sync_lock);
> > +
> > + mutex_lock(&sobj->robj->lock);
> > + sobj->robj->locked = false;
> > + mutex_unlock(&sobj->robj->lock);
> > + }
> > +
> > + mutex_unlock(&sync->lock);
> > +
> > + if (ctx)
> > + ww_acquire_fini(ctx);
> > +
> > + del_timer(&sync->timer);
> > +}
> > +
> > +/**
> > + * is_dmabuf_sync_supported - Check if dmabuf sync is supported or not.
> > + */
> > +bool is_dmabuf_sync_supported(void)
> > +{
> > + return dmabuf_sync_enabled == 1;
> > +}
> > +EXPORT_SYMBOL(is_dmabuf_sync_supported);
>
> _GPL ?
>
> I would also prefix it with 'dmabuf_is_sync_supported' just to make
> all of the libraries call start with 'dmabuf'
>
Seems better. Will change it to dmabuf_is_sync_supported, and use
EXPORT_SYMBOL_GPL.
> > +
> > +/**
> > + * dmabuf_sync_init - Allocate and initialize a dmabuf sync.
> > + *
> > + * @priv: A device private data.
> > + * @name: A sync object name.
> > + *
> > + * This function should be called when a device context or an event
> > + * context such as a page flip event is created. And the created
> > + * dmabuf_sync object should be set to the context.
> > + * The caller can get a new sync object for buffer synchronization
> > + * through this function.
> > + */
> > +struct dmabuf_sync *dmabuf_sync_init(const char *name,
> > + struct dmabuf_sync_priv_ops *ops,
> > + void *priv)
> > +{
> > + struct dmabuf_sync *sync;
> > +
> > + sync = kzalloc(sizeof(*sync), GFP_KERNEL);
> > + if (!sync)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + strncpy(sync->name, name, ARRAY_SIZE(sync->name) - 1);
> > +
>
> That is odd usage of an ARRAY_SIZE, but I can see how you can use it.
> I would say you should just do a #define for the 64 line and use that
> instead.
>
Ok, will use the macro instead.
> > + sync->ops = ops;
> > + sync->priv = priv;
> > + INIT_LIST_HEAD(&sync->syncs);
> > + mutex_init(&sync->lock);
> > + INIT_WORK(&sync->work, dmabuf_sync_timeout_worker);
> > +
> > + return sync;
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_init);
>
> _GPL ?
Sure.
> > +
> > +/**
> > + * dmabuf_sync_fini - Release a given dmabuf sync.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + *
> > + * This function should be called if some operation is failed after
> > + * dmabuf_sync_init call to release relevant resources, and after
> > + * dmabuf_sync_unlock function is called.
> > + */
> > +void dmabuf_sync_fini(struct dmabuf_sync *sync)
> > +{
> > + if (WARN_ON(!sync))
> > + return;
> > +
> > + if (sync->ops && sync->ops->free)
> > + sync->ops->free(sync->priv);
> > +
>
> No need to cancel the sync->work in case that is still
> running?
Right, the locks to all buffers should be canceled if dmabuf_sync_fini was
called without unlock call.
>
> > + kfree(sync);
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_fini);
>
> _GPL ?
> > +
> > +/*
> > + * dmabuf_sync_get_obj - Add a given object to syncs list.
>
> sync's list I think?
>
Ok, seems better.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + * @dmabuf: An object to dma_buf structure.
> > + * @type: A access type to a dma buf.
> > + * The DMA_BUF_ACCESS_R means that this dmabuf could be accessed by
> > + * others for read access. On the other hand, the DMA_BUF_ACCESS_W
> > + * means that this dmabuf couldn't be accessed by others but would be
> > + * accessed by caller's dma exclusively. And the DMA_BUF_ACCESS_DMA
> can be
> > + * combined.
>
> Should this be an enum?
> > + *
> > + * This function creates and initializes a new dmabuf sync object and
> it adds
> > + * the dmabuf sync object to syncs list to track and manage all
dmabufs.
> > + */
> > +static int dmabuf_sync_get_obj(struct dmabuf_sync *sync, struct dma_buf
> *dmabuf,
> > + unsigned int type)
>
> enum for 'type'?
> > +{
> > + struct dmabuf_sync_object *sobj;
> > +
> > + if (!dmabuf->sync) {
> > + WARN_ON(1);
> > + return -EFAULT;
> > + }
> > +
> > + if (!IS_VALID_DMA_BUF_ACCESS_TYPE(type))
> > + return -EINVAL;
> > +
> > + if ((type & DMA_BUF_ACCESS_RW) == DMA_BUF_ACCESS_RW)
> > + type &= ~DMA_BUF_ACCESS_R;
>
> Ah, that is why you are not using an enum.
>
> > +
> > + sobj = kzalloc(sizeof(*sobj), GFP_KERNEL);
> > + if (!sobj) {
> > + WARN_ON(1);
>
> I think you can skip that WARN_ON. Handling an -ENOMEM should be
> something fairly easy to handle by the calleer.
>
Ok, will remove it.
> > + return -ENOMEM;
> > + }
> > +
> > + get_dma_buf(dmabuf);
> > +
> > + sobj->dmabuf = dmabuf;
> > + sobj->robj = dmabuf->sync;
> > + sobj->access_type = type;
> > +
> > + mutex_lock(&sync->lock);
> > + list_add_tail(&sobj->head, &sync->syncs);
> > + mutex_unlock(&sync->lock);
> > +
> > + return 0;
> > +}
> > +
> > +/*
> > + * dmabuf_sync_put_obj - Release a given sync object.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + *
> > + * This function should be called if some operation is failed after
>
> s/is//
Sure.
> > + * dmabuf_sync_get_obj call to release a given sync object.
> > + */
> > +static void dmabuf_sync_put_obj(struct dmabuf_sync *sync,
> > + struct dma_buf *dmabuf)
> > +{
> > + struct dmabuf_sync_object *sobj;
> > +
> > + mutex_lock(&sync->lock);
> > +
> > + list_for_each_entry(sobj, &sync->syncs, head) {
> > + if (sobj->dmabuf != dmabuf)
> > + continue;
> > +
> > + dma_buf_put(sobj->dmabuf);
> > +
> > + list_del_init(&sobj->head);
> > + kfree(sobj);
> > + break;
> > + }
> > +
> > + if (list_empty(&sync->syncs))
> > + sync->status = 0;
> > +
> > + mutex_unlock(&sync->lock);
> > +}
> > +
> > +/*
> > + * dmabuf_sync_put_objs - Release all sync objects of dmabuf_sync.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + *
> > + * This function should be called if some operation is failed after
>
> s/is//
Sure.
>
> > + * dmabuf_sync_get_obj call to release all sync objects.
> > + */
> > +static void dmabuf_sync_put_objs(struct dmabuf_sync *sync)
> > +{
> > + struct dmabuf_sync_object *sobj, *next;
> > +
> > + mutex_lock(&sync->lock);
> > +
> > + list_for_each_entry_safe(sobj, next, &sync->syncs, head) {
> > + dma_buf_put(sobj->dmabuf);
> > +
> > + list_del_init(&sobj->head);
> > + kfree(sobj);
> > + }
> > +
> > + mutex_unlock(&sync->lock);
> > +
> > + sync->status = 0;
> > +}
> > +
> > +/**
> > + * dmabuf_sync_lock - lock all dmabufs added to syncs list.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + *
> > + * The caller should call this function prior to CPU or DMA access to
> > + * the dmabufs so that others can not access the dmabufs.
> > + * Internally, this function avoids dead lock issue with ww-mutex.
> > + */
> > +int dmabuf_sync_lock(struct dmabuf_sync *sync)
> > +{
> > + int ret;
> > +
> > + if (!sync) {
> > + WARN_ON(1);
> > + return -EFAULT;
> > + }
> > +
> > + if (list_empty(&sync->syncs))
> > + return -EINVAL;
> > +
> > + if (sync->status != DMABUF_SYNC_GOT)
> > + return -EINVAL;
> > +
> > + ret = dmabuf_sync_lock_objs(sync, &sync->ctx);
> > + if (ret < 0) {
> > + WARN_ON(1);
>
> Perhaps also include the ret value in the WARN?
>
> > + return ret;
> > + }
> > +
> > + sync->status = DMABUF_SYNC_LOCKED;
> > +
> > + return ret;
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_lock);
>
> I think you know what I am going to say.
> > +
> > +/**
> > + * dmabuf_sync_unlock - unlock all objects added to syncs list.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + *
> > + * The caller should call this function after CPU or DMA access to
> > + * the dmabufs is completed so that others can access the dmabufs.
> > + */
> > +int dmabuf_sync_unlock(struct dmabuf_sync *sync)
> > +{
> > + if (!sync) {
> > + WARN_ON(1);
> > + return -EFAULT;
> > + }
> > +
> > + /* If current dmabuf sync object wasn't reserved then just return.
> */
> > + if (sync->status != DMABUF_SYNC_LOCKED)
> > + return -EAGAIN;
> > +
> > + dmabuf_sync_unlock_objs(sync, &sync->ctx);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_unlock);
> > +
> > +/**
> > + * dmabuf_sync_single_lock - lock a dma buf.
> > + *
> > + * @dmabuf: A dma buf object that tries to lock.
> > + * @type: A access type to a dma buf.
> > + * The DMA_BUF_ACCESS_R means that this dmabuf could be accessed by
> > + * others for read access. On the other hand, the DMA_BUF_ACCESS_W
> > + * means that this dmabuf couldn't be accessed by others but would be
> > + * accessed by caller's dma exclusively. And the DMA_BUF_ACCESS_DMA
> can
> > + * be combined with other.
> > + * @wait: Indicate whether caller is blocked or not.
> > + * true means that caller will be blocked, and false means that this
> > + * function will return -EAGAIN if this caller can't take the lock
> > + * right now.
> > + *
> > + * The caller should call this function prior to CPU or DMA access to
> the dmabuf
> > + * so that others cannot access the dmabuf.
> > + */
> > +int dmabuf_sync_single_lock(struct dma_buf *dmabuf, unsigned int type,
> > + bool wait)
> > +{
> > + struct dmabuf_sync_reservation *robj;
> > +
> > + if (!dmabuf->sync) {
> > + WARN_ON(1);
> > + return -EFAULT;
> > + }
> > +
> > + if (!IS_VALID_DMA_BUF_ACCESS_TYPE(type)) {
> > + WARN_ON(1);
> > + return -EINVAL;
> > + }
> > +
> > + get_dma_buf(dmabuf);
> > + robj = dmabuf->sync;
> > +
> > + mutex_lock(&robj->lock);
> > +
> > + /* Don't lock in case of read and read. */
> > + if (robj->accessed_type & DMA_BUF_ACCESS_R && type &
> DMA_BUF_ACCESS_R) {
> > + atomic_inc(&robj->shared_cnt);
> > + mutex_unlock(&robj->lock);
> > + return 0;
> > + }
> > +
> > + /*
> > + * In case of F_SETLK, just return -EAGAIN if this dmabuf has
> already
> > + * been locked.
> > + */
> > + if (!wait && robj->locked) {
> > + mutex_unlock(&robj->lock);
> > + dma_buf_put(dmabuf);
> > + return -EAGAIN;
> > + }
> > +
> > + mutex_unlock(&robj->lock);
> > +
> > + mutex_lock(&robj->sync_lock.base);
> > +
> > + mutex_lock(&robj->lock);
> > + robj->locked = true;
> > + mutex_unlock(&robj->lock);
>
> Are you missing an mutex_unlock on &robj->sync_lock.base?
> Oh wait, that is the purpose of this code. You might want
> to put a nice comment right above that and say: "Unlocked
> by dmabuf_sync_single_unlock"
Will add the comment.
>
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_single_lock);
> > +
> > +/**
> > + * dmabuf_sync_single_unlock - unlock a dma buf.
> > + *
> > + * @dmabuf: A dma buf object that tries to unlock.
> > + *
> > + * The caller should call this function after CPU or DMA access to
> > + * the dmabuf is completed so that others can access the dmabuf.
> > + */
> > +void dmabuf_sync_single_unlock(struct dma_buf *dmabuf)
> > +{
> > + struct dmabuf_sync_reservation *robj;
> > +
> > + if (!dmabuf->sync) {
> > + WARN_ON(1);
> > + return;
> > + }
> > +
> > + robj = dmabuf->sync;
> > +
> > + mutex_lock(&robj->lock);
> > +
> > + if (robj->polled) {
> > + robj->poll_event = true;
> > + robj->polled = false;
> > + wake_up_interruptible(&robj->poll_wait);
> > + }
> > +
> > + if (atomic_add_unless(&robj->shared_cnt, -1 , 1)) {
> > + mutex_unlock(&robj->lock);
> > + dma_buf_put(dmabuf);
> > + return;
> > + }
> > +
> > + mutex_unlock(&robj->lock);
> > +
> > + mutex_unlock(&robj->sync_lock.base);
> > +
> > + mutex_lock(&robj->lock);
> > + robj->locked = false;
> > + mutex_unlock(&robj->lock);
> > +
> > + dma_buf_put(dmabuf);
> > +
> > + return;
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_single_unlock);
> > +
> > +/**
> > + * dmabuf_sync_get - Get dmabuf sync object.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + * @sync_buf: A dmabuf object to be synchronized with others.
> > + * @type: A access type to a dma buf.
> > + * The DMA_BUF_ACCESS_R means that this dmabuf could be accessed by
> > + * others for read access. On the other hand, the DMA_BUF_ACCESS_W
> > + * means that this dmabuf couldn't be accessed by others but would be
> > + * accessed by caller's dma exclusively. And the DMA_BUF_ACCESS_DMA
> can
> > + * be combined with other.
> > + *
> > + * This function should be called after dmabuf_sync_init function is
> called.
> > + * The caller can tie up multiple dmabufs into one sync object by
> calling this
> > + * function several times. Internally, this function allocates
> > + * a dmabuf_sync_object and adds a given dmabuf to it, and also takes
> > + * a reference to a dmabuf.
> > + */
> > +int dmabuf_sync_get(struct dmabuf_sync *sync, void *sync_buf, unsigned
> int type)
> > +{
> > + int ret;
> > +
> > + if (!sync || !sync_buf) {
> > + WARN_ON(1);
> > + return -EFAULT;
> > + }
> > +
> > + ret = dmabuf_sync_get_obj(sync, sync_buf, type);
> > + if (ret < 0) {
> > + WARN_ON(1);
> > + return ret;
> > + }
> > +
> > + sync->status = DMABUF_SYNC_GOT;
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_get);
> > +
> > +/**
> > + * dmabuf_sync_put - Put dmabuf sync object to a given dmabuf.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + * @dmabuf: An dmabuf object.
> > + *
> > + * This function should be called if some operation is failed after
> > + * dmabuf_sync_get function is called to release the dmabuf, or
> > + * dmabuf_sync_unlock function is called. Internally, this function
> > + * removes a given dmabuf from a sync object and remove the sync
object.
> > + * At this time, the dmabuf is putted.
> > + */
> > +void dmabuf_sync_put(struct dmabuf_sync *sync, struct dma_buf *dmabuf)
> > +{
> > + if (!sync || !dmabuf) {
> > + WARN_ON(1);
> > + return;
> > + }
> > +
> > + if (list_empty(&sync->syncs))
> > + return;
> > +
> > + dmabuf_sync_put_obj(sync, dmabuf);
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_put);
> > +
> > +/**
> > + * dmabuf_sync_put_all - Put dmabuf sync object to dmabufs.
> > + *
> > + * @sync: An object to dmabuf_sync structure.
> > + *
> > + * This function should be called if some operation is failed after
> > + * dmabuf_sync_get function is called to release all sync objects, or
> > + * dmabuf_sync_unlock function is called. Internally, this function
> > + * removes dmabufs from a sync object and remove the sync object.
> > + * At this time, all dmabufs are putted.
> > + */
> > +void dmabuf_sync_put_all(struct dmabuf_sync *sync)
> > +{
> > + if (!sync) {
> > + WARN_ON(1);
> > + return;
> > + }
> > +
> > + if (list_empty(&sync->syncs))
> > + return;
> > +
> > + dmabuf_sync_put_objs(sync);
> > +}
> > +EXPORT_SYMBOL(dmabuf_sync_put_all);
> > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> > index dfac5ed..0109673 100644
> > --- a/include/linux/dma-buf.h
> > +++ b/include/linux/dma-buf.h
> > @@ -115,6 +115,7 @@ struct dma_buf_ops {
> > * @exp_name: name of the exporter; useful for debugging.
> > * @list_node: node for dma_buf accounting and debugging.
> > * @priv: exporter specific private data for this buffer object.
> > + * @sync: sync object linked to this dma-buf
> > */
> > struct dma_buf {
> > size_t size;
> > @@ -128,6 +129,7 @@ struct dma_buf {
> > const char *exp_name;
> > struct list_head list_node;
> > void *priv;
> > + void *sync;
> > };
> >
> > /**
> > @@ -148,6 +150,20 @@ struct dma_buf_attachment {
> > void *priv;
> > };
> >
> > +#define DMA_BUF_ACCESS_R 0x1
> > +#define DMA_BUF_ACCESS_W 0x2
> > +#define DMA_BUF_ACCESS_DMA 0x4
> > +#define DMA_BUF_ACCESS_RW (DMA_BUF_ACCESS_R | DMA_BUF_ACCESS_W)
> > +#define DMA_BUF_ACCESS_DMA_R (DMA_BUF_ACCESS_R |
DMA_BUF_ACCESS_DMA)
> > +#define DMA_BUF_ACCESS_DMA_W (DMA_BUF_ACCESS_W |
DMA_BUF_ACCESS_DMA)
> > +#define DMA_BUF_ACCESS_DMA_RW (DMA_BUF_ACCESS_DMA_R |
> DMA_BUF_ACCESS_DMA_W)
> > +#define IS_VALID_DMA_BUF_ACCESS_TYPE(t) (t == DMA_BUF_ACCESS_R || \
> > + t == DMA_BUF_ACCESS_W || \
> > + t == DMA_BUF_ACCESS_DMA_R || \
> > + t == DMA_BUF_ACCESS_DMA_W || \
> > + t == DMA_BUF_ACCESS_RW || \
> > + t == DMA_BUF_ACCESS_DMA_RW)
> > +
> > /**
> > * get_dma_buf - convenience wrapper for get_file.
> > * @dmabuf: [in] pointer to dma_buf
> > diff --git a/include/linux/dmabuf-sync.h b/include/linux/dmabuf-sync.h
> > new file mode 100644
> > index 0000000..9a3afc4
> > --- /dev/null
> > +++ b/include/linux/dmabuf-sync.h
> > @@ -0,0 +1,190 @@
> > +/*
> > + * Copyright (C) 2013 Samsung Electronics Co.Ltd
> > + * Authors:
> > + * Inki Dae <inki.dae at samsung.com>
> > + *
> > + * This program is free software; you can redistribute it and/or
> modify it
> > + * under the terms of the GNU General Public License as published by
> the
> > + * Free Software Foundation; either version 2 of the License, or (at
> your
> > + * option) any later version.
> > + *
> > + */
> > +
> > +#include <linux/mutex.h>
> > +#include <linux/sched.h>
> > +#include <linux/dma-buf.h>
> > +
> > +enum dmabuf_sync_status {
> > + DMABUF_SYNC_GOT = 1,
> > + DMABUF_SYNC_LOCKED,
> > +};
> > +
>
> No comment about this structure?
Will add comments.
>
> > +struct dmabuf_sync_reservation {
> > + struct ww_mutex sync_lock;
> > + struct mutex lock;
> > + wait_queue_head_t poll_wait;
> > + unsigned int poll_event;
> > + unsigned int polled;
> > + atomic_t shared_cnt;
> > + unsigned int accessed_type;
> > + unsigned int locked;
> > +};
> > +
> > +/*
> > + * A structure for dmabuf_sync_object.
> > + *
> > + * @head: A list head to be added to syncs list.
> > + * @robj: A reservation_object object.
> > + * @dma_buf: A dma_buf object.
> > + * @access_type: Indicate how a current task tries to access
> > + * a given buffer.
>
> Huh? What values are expected then? Is there some #define or enum
> for that?
>
Right, there are definitions for that. Will add more comments.
> > + */
> > +struct dmabuf_sync_object {
> > + struct list_head head;
> > + struct dmabuf_sync_reservation *robj;
> > + struct dma_buf *dmabuf;
> > + unsigned int access_type;
> > +};
> > +
> > +struct dmabuf_sync_priv_ops {
> > + void (*free)(void *priv);
> > +};
> > +
> > +/*
> > + * A structure for dmabuf_sync.
> > + *
> > + * @syncs: A list head to sync object and this is global to system.
> > + * @list: A list entry used as committed list node
> > + * @lock: A mutex lock to current sync object.
>
> You should say for which specific operations this mutex is needed.
> For everything? Or just for list operations.
Ok, will add more comments.
>
> > + * @ctx: A current context for ww mutex.
> > + * @work: A work struct to release resources at timeout.
> > + * @priv: A private data.
> > + * @name: A string to dmabuf sync owner.
> > + * @timer: A timer list to avoid lockup and release resources.
> > + * @status: Indicate current status (DMABUF_SYNC_GOT or
> DMABUF_SYNC_LOCKED).
> > + */
> > +struct dmabuf_sync {
> > + struct list_head syncs;
> > + struct list_head list;
> > + struct mutex lock;
> > + struct ww_acquire_ctx ctx;
> > + struct work_struct work;
> > + void *priv;
> > + struct dmabuf_sync_priv_ops *ops;
> > + char name[64];
>
> Perhaps a #define for the size?
Ok, will use macro instead.
>
> > + struct timer_list timer;
> > + unsigned int status;
> > +};
> > +
> > +#ifdef CONFIG_DMABUF_SYNC
> > +
> > +extern struct ww_class dmabuf_sync_ww_class;
> > +
> > +static inline void dmabuf_sync_reservation_init(struct dma_buf *dmabuf)
> > +{
> > + struct dmabuf_sync_reservation *obj;
> > +
> > + obj = kzalloc(sizeof(*obj), GFP_KERNEL);
> > + if (!obj)
> > + return;
> > +
> > + dmabuf->sync = obj;
> > +
> > + ww_mutex_init(&obj->sync_lock, &dmabuf_sync_ww_class);
> > +
> > + mutex_init(&obj->lock);
> > + atomic_set(&obj->shared_cnt, 1);
> > +
> > + init_waitqueue_head(&obj->poll_wait);
> > +}
> > +
> > +static inline void dmabuf_sync_reservation_fini(struct dma_buf *dmabuf)
> > +{
> > + struct dmabuf_sync_reservation *obj;
> > +
> > + if (!dmabuf->sync)
> > + return;
> > +
> > + obj = dmabuf->sync;
> > +
> > + ww_mutex_destroy(&obj->sync_lock);
> > +
> > + kfree(obj);
> > +}
> > +
> > +extern bool is_dmabuf_sync_supported(void);
> > +
> > +extern struct dmabuf_sync *dmabuf_sync_init(const char *name,
> > + struct dmabuf_sync_priv_ops *ops,
> > + void *priv);
> > +
> > +extern void dmabuf_sync_fini(struct dmabuf_sync *sync);
> > +
> > +extern int dmabuf_sync_lock(struct dmabuf_sync *sync);
> > +
> > +extern int dmabuf_sync_unlock(struct dmabuf_sync *sync);
> > +
> > +int dmabuf_sync_single_lock(struct dma_buf *dmabuf, unsigned int type,
> > + bool wait);
> > +
> > +void dmabuf_sync_single_unlock(struct dma_buf *dmabuf);
> > +
> > +extern int dmabuf_sync_get(struct dmabuf_sync *sync, void *sync_buf,
> > + unsigned int type);
> > +
> > +extern void dmabuf_sync_put(struct dmabuf_sync *sync, struct dma_buf
> *dmabuf);
> > +
> > +extern void dmabuf_sync_put_all(struct dmabuf_sync *sync);
> > +
> > +#else
> > +
> > +static inline void dmabuf_sync_reservation_init(struct dma_buf *dmabuf)
> { }
> > +
> > +static inline void dmabuf_sync_reservation_fini(struct dma_buf *dmabuf)
> { }
> > +
> > +static inline bool is_dmabuf_sync_supported(void) { return false; }
> > +
> > +static inline struct dmabuf_sync *dmabuf_sync_init(const char *name,
> > + struct dmabuf_sync_priv_ops *ops,
> > + void *priv)
> > +{
> > + return ERR_PTR(0);
> > +}
> > +
> > +static inline void dmabuf_sync_fini(struct dmabuf_sync *sync) { }
> > +
> > +static inline int dmabuf_sync_lock(struct dmabuf_sync *sync)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline int dmabuf_sync_unlock(struct dmabuf_sync *sync)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline int dmabuf_sync_single_lock(struct dma_buf *dmabuf,
> > + unsigned int type,
> > + bool wait)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void dmabuf_sync_single_unlock(struct dma_buf *dmabuf)
> > +{
> > + return;
> > +}
> > +
> > +static inline int dmabuf_sync_get(struct dmabuf_sync *sync,
> > + void *sync_buf,
> > + unsigned int type)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void dmabuf_sync_put(struct dmabuf_sync *sync,
> > + struct dma_buf *dmabuf) { }
> > +
> > +static inline void dmabuf_sync_put_all(struct dmabuf_sync *sync) { }
> > +
> > +#endif
> > --
> > 1.7.5.4
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
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