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| Filename | Latest commit message | Latest commit date |
|---|---|---|
fc8548c75c
commit 57e9af7831dcf211c5c689c2a6f209f4abdf0bce upstream.
As DMA Rx can be completed from two places, it is possible that DMA Rx
completes before DMA completion callback had a chance to complete it.
Once the previous DMA Rx has been completed, a new one can be started
on the next UART interrupt. The following race is possible
(uart_unlock_and_check_sysrq_irqrestore() replaced with
spin_unlock_irqrestore() for simplicity/clarity):
CPU0 CPU1
dma_rx_complete()
serial8250_handle_irq()
spin_lock_irqsave(&port->lock)
handle_rx_dma()
serial8250_rx_dma_flush()
__dma_rx_complete()
dma->rx_running = 0
// Complete DMA Rx
spin_unlock_irqrestore(&port->lock)
serial8250_handle_irq()
spin_lock_irqsave(&port->lock)
handle_rx_dma()
serial8250_rx_dma()
dma->rx_running = 1
// Setup a new DMA Rx
spin_unlock_irqrestore(&port->lock)
spin_lock_irqsave(&port->lock)
// sees dma->rx_running = 1
__dma_rx_complete()
dma->rx_running = 0
// Incorrectly complete
// running DMA Rx
This race seems somewhat theoretical to occur for real but handle it
correctly regardless. Check what is the DMA status before complething
anything in __dma_rx_complete().
Reported-by: Gilles BULOZ <gilles.buloz@kontron.com>
Tested-by: Gilles BULOZ <gilles.buloz@kontron.com>
Fixes:
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| certs | ||
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
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| kernel | ||
| lib | ||
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| net | ||
| samples | ||
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| virt | ||
| .clang-format | ||
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| README | ||
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.