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Below is a summary of a discussion about the Workqueue API and cpu isolation considerations. Details and more information are available here: "workqueue: Always use wq_select_unbound_cpu() for WORK_CPU_UNBOUND." https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/ === Current situation: problems === Let's consider a nohz_full system with isolated CPUs: wq_unbound_cpumask is set to the housekeeping CPUs, for !WQ_UNBOUND the local CPU is selected. This leads to different scenarios if a work item is scheduled on an isolated CPU where "delay" value is 0 or greater then 0: schedule_delayed_work(, 0); This will be handled by __queue_work() that will queue the work item on the current local (isolated) CPU, while: schedule_delayed_work(, 1); Will move the timer on an housekeeping CPU, and schedule the work there. Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. === Plan and future plans === This patchset is the first stone on a refactoring needed in order to address the points aforementioned; it will have a positive impact also on the cpu isolation, in the long term, moving away percpu workqueue in favor to an unbound model. These are the main steps: 1) API refactoring (that this patch is introducing) - Make more clear and uniform the system wq names, both per-cpu and unbound. This to avoid any possible confusion on what should be used. - Introduction of WQ_PERCPU: this flag is the complement of WQ_UNBOUND, introduced in this patchset and used on all the callers that are not currently using WQ_UNBOUND. WQ_UNBOUND will be removed in a future release cycle. Most users don't need to be per-cpu, because they don't have locality requirements, because of that, a next future step will be make "unbound" the default behavior. 2) Check who really needs to be per-cpu - Remove the WQ_PERCPU flag when is not strictly required. 3) Add a new API (prefer local cpu) - There are users that don't require a local execution, like mentioned above; despite that, local execution yeld to performance gain. This new API will prefer the local execution, without requiring it. === Introduced Changes by this series === 1) [P 1] Replace use of system_wq system_wq is a per-CPU worqueue, replaced by system_percpu_wq. Despite that, system_wq in this change has been replaced by system_dfl_wq, because there aren't per-cpu variables. Thanks! --- Changes in v2: - Removed 1/2 from the series because already applied - Instead of rename system_wq with system_percpu_wq, [P 1] change the workqueue using system_dfl_wq (the new unbound workqueue). Marco Crivellari (1): ASoC: replace use of system_wq with system_dfl_wq sound/soc/codecs/aw88081.c | 2 +- sound/soc/codecs/aw88166.c | 2 +- sound/soc/codecs/aw88261.c | 2 +- sound/soc/codecs/aw88395/aw88395.c | 2 +- sound/soc/codecs/aw88399.c | 2 +- sound/soc/codecs/cs42l43-jack.c | 2 +- sound/soc/codecs/cs42l43.c | 4 ++-- sound/soc/codecs/es8326.c | 12 ++++++------ sound/soc/codecs/rt5663.c | 6 +++--- sound/soc/intel/boards/sof_es8336.c | 2 +- sound/soc/sof/intel/cnl.c | 2 +- sound/soc/sof/intel/hda-ipc.c | 2 +- 12 files changed, 20 insertions(+), 20 deletions(-) -- 2.51.0