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The mailbox sends a request to the controller and the tx_done callback received for that request clears the active_req pointer. The callback sends the next request in the queue, if there is one. When a controller is busy and cannot accept any more requests until the interrupt is cleared, it would return -EAGAIN. The mailbox controller must unlock its spinlock and retry again. An incorrect check for the -EAGAIN allows, the mailbox to send multiple requests without receiving the tx_done callback for the first one sent. As a result, the active_req pointer is overwritten and holds on only to the last request sent. When the second tx_done is received it finds the active_req to be NULL already and bails out before notifying the client. The client may wait forever for this response. Change-Id: Id58c7365be8c6bfc7f90fe9445c88c1246d2d7f8 Signed-off-by: Lina Iyer <ilina@codeaurora.org>
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.