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801afdfbfc
When a cpuset isolated partition is created / updated or destroyed, the interrupt threads are affined blindly to all the non-isolated CPUs. This happens without taking into account the interrupt threads initial affinity that becomes ignored. For example in a system with 8 CPUs, if an interrupt and its kthread are initially affine to CPU 5, creating an isolated partition with only CPU 2 inside will eventually end up affining the interrupt kthread to all CPUs but CPU 2 (that is CPUs 0,1,3-7), losing the kthread preference for CPU 5. Besides the blind re-affining, this doesn't take care of the actual low level interrupt which isn't migrated. As of today the only way to isolate non managed interrupts, along with their kthreads, is to overwrite their affinity separately, for example through /proc/irq/ To avoid doing that manually, future development should focus on updating the interrupt's affinity whenever cpuset isolated partitions are updated. In the meantime, cpuset shouldn't fiddle with interrupt threads directly. To prevent from that, set the PF_NO_SETAFFINITY flag to them. This is done through kthread_bind_mask() by affining them initially to all possible CPUs as at that point the interrupt is not started up which means the affinity of the hard interrupt is not known. The thread will adjust that once it reaches the handler, which is guaranteed to happen after the initial affinity of the hard interrupt is established. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://patch.msgid.link/20251121143500.42111-3-frederic@kernel.org |
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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 reStructuredText 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.