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The rx_dma() callback (omap_8250_rx_dma) accesses UART_IER. This register is modified twice by each console write (serial8250_console_write()) under the port lock. However, not all calls to the rx_dma() callback are under the port lock. Add the missing port locking around rx_dma() callback calls. Add lockdep notation to the omap_8250_rx_dma(). Note that this is not fixing a real problem because: 1. Currently DMA is forced off for 8250_omap consoles. 2. The serial devices are resumed before console printing is enabled. However, adding this locking allows for clean locking semantics for the rx_dma() callback so that lockdep can be used to identify possible problems in the future. It also simplifies synchronization of UART_IER in general by not needing to rely on implementation details such as 1 and 2. Signed-off-by: John Ogness <john.ogness@linutronix.de> Link: https://lore.kernel.org/r/20230525093159.223817-6-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.