iio: core: Don't free buffer0 blocks when it's still in use via buffer fd API#3318
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iio: core: Don't free buffer0 blocks when it's still in use via buffer fd API#3318nunojsa wants to merge 1 commit into
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…r fd API When a user opens /dev/iio:deviceN to issue IIO_BUFFER_GET_FD_IOCTL for any buffer (including buffer0), the chrdev must be opened and then closed. On close, iio_chrdev_release() unconditionally frees buffer0's mmap blocks via iio_buffer_free_blocks(). This is wrong when buffer0 is actively streaming through its own per-buffer fd — the chrdev close destroys the blocks and kills the stream. Guard the iio_buffer_free_blocks() call by checking buffer0's IIO_BUSY_BIT_POS flag. If buffer0's fd is still open and active, its blocks are managed by the buffer's own fd and will be freed in iio_buffer_chrdev_release() instead. Signed-off-by: Nuno Sá <nuno.sa@analog.com>
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When a user opens /dev/iio:deviceN to issue IIO_BUFFER_GET_FD_IOCTL for any buffer (including buffer0), the chrdev must be opened and then closed. On close, iio_chrdev_release() unconditionally frees buffer0's mmap blocks via iio_buffer_free_blocks().
This is wrong when buffer0 is actively streaming through its own per-buffer fd — the chrdev close destroys the blocks and kills the stream.
Guard the iio_buffer_free_blocks() call by checking buffer0's IIO_BUSY_BIT_POS flag. If buffer0's fd is still open and active, its blocks are managed by the buffer's own fd and will be freed in iio_buffer_chrdev_release() instead.
This becomes a problem with multi buffer support when userspace (rightfully) opens the main chardev to get the buffer handle and then closes it again.
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