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Interrupt handlers called by soft-pending irq replay code can run softirqs, softirq replay enables and disables local irqs, which allows interrupts to come in including soft-masked interrupts, and it can cause pending irqs to be replayed again. That makes the soft irq replay state machine and possible races more complicated and fragile than it needs to be. Use irq_enter/irq_exit around irq replay to prevent softirqs running while interrupts are being replayed. Softirqs will now be run at the irq_exit() call after all the irq replaying is done. This prevents irqs being replayed while irqs are being replayed, and should hopefully make things simpler and easier to think about and debug. A new PACA_IRQ_REPLAYING is added to prevent asynchronous interrupt handlers hard-enabling EE while pending irqs are being replayed, because that causes new pending irqs to arrive which is also a complexity. This means pending irqs won't be profiled quite so well because perf irqs can't be taken. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20230121102618.2824429-1-npiggin@gmail.com
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.