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![]() The workqueue code has it's internal spinlock (pool::lock) and also implicit spinlock usage in the wq_manager waitqueue. These spinlocks are converted to 'sleeping' spinlocks on a RT-kernel. Workqueue functions can be invoked from contexts which are truly atomic even on a PREEMPT_RT enabled kernel. Taking sleeping locks from such contexts is forbidden. pool::lock can be converted to a raw spinlock as the lock held times are short. But the workqueue manager waitqueue is handled inside of pool::lock held regions which again violates the lock nesting rules of raw and regular spinlocks. The manager waitqueue has no special requirements like custom wakeup callbacks or mass wakeups. While it does not use exclusive wait mode explicitly there is no strict requirement to queue the waiters in a particular order as there is only one waiter at a time. This allows to replace the waitqueue with rcuwait which solves the locking problem because rcuwait relies on existing locking. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Tejun Heo <tj@kernel.org> |
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crypto | ||
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drivers | ||
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include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
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security | ||
sound | ||
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virt | ||
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COPYING | ||
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MAINTAINERS | ||
Makefile | ||
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.