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[ Upstream commit796a2665ca] On arm imx6, when opening the chip's netdev, the whole Linux kernel intermittently hangs/freezes. This is caused by a bug in the driver code which tests if pcie interrupts are working correctly, using the software interrupt: 1. open: enable the software interrupt 2. open: tell the chip to assert the software interrupt 3. open: wait for flag 4. ISR: acknowledge s/w interrupt, set flag 5. open: notice flag, disable the s/w interrupt, continue Unfortunately the ISR only acknowledges the s/w interrupt, but does not disable it. This will re-trigger the ISR in a tight loop. On some (lucky) platforms, open proceeds to disable the s/w interrupt even while the ISR is 'spinning'. On arm imx6, the spinning ISR does not allow open to proceed, resulting in a hung Linux kernel. Fix minimally by disabling the s/w interrupt in the ISR, which will prevent it from spinning. This won't break anything because the s/w interrupt is used as a one-shot interrupt. Note that this is a minimal fix, overlooking many possible cleanups, e.g.: - lan743x_intr_software_isr() is completely redundant and reads INT_STS twice for no apparent reason - disabling the s/w interrupt in lan743x_intr_test_isr() is now redundant, but harmless - waiting on software_isr_flag can be converted from a sleeping poll loop to wait_event_timeout() Fixes:23f0703c12("lan743x: Add main source files for new lan743x driver") Tested-by: Sven Van Asbroeck <thesven73@gmail.com> # arm imx6 lan7430 Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com> Link: https://lore.kernel.org/r/20201112204741.12375-1-TheSven73@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 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.
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.