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It has been reported that isolated CPUs can suffer from interference due to per-CPU kworkers waking up just to die. A surge of workqueue activity during initial setup of a latency-sensitive application (refresh_vm_stats() being one of the culprits) can cause extra per-CPU kworkers to be spawned. Then, said latency-sensitive task can be running merrily on an isolated CPU only to be interrupted sometime later by a kworker marked for death (cf. IDLE_WORKER_TIMEOUT, 5 minutes after last kworker activity). Prevent this by affining kworkers to the wq_unbound_cpumask (which doesn't contain isolated CPUs, cf. HK_TYPE_WQ) before waking them up after marking them with WORKER_DIE. Changing the affinity does require a sleepable context, leverage the newly introduced pool->idle_cull_work to get that. Remove dying workers from pool->workers and keep track of them in a separate list. This intentionally prevents for_each_loop_worker() from iterating over workers that are marked for death. Rename destroy_worker() to set_working_dying() to better reflect its effects and relationship with wake_dying_workers(). Signed-off-by: Valentin Schneider <vschneid@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.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.
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.