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If two concurrent threads call pl330_get_desc() when DMAC descriptor pool is empty it is possible that allocation for one of threads will fail with message: kernel: dma-pl330 20078000.dma-controller: pl330_get_desc:2469 ALERT! Here how that can happen. Thread A calls pl330_get_desc() to get descriptor. If DMAC descriptor pool is empty pl330_get_desc() allocates new descriptor on shared pool using add_desc() and then get newly allocated descriptor using pluck_desc(). At the same time thread B calls pluck_desc() and take newly allocated descriptor. In that case descriptor allocation for thread A will fail. Using on-stack pool for new descriptor allow avoid the issue described. The patch modify pl330_get_desc() to use on-stack pool for allocation new descriptors. Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.