create_worker() will already set the right affinity using kthread_bind_mask(), this means only the rescuer will need to change it's affinity. Howveer, while in cpu-hot-unplug a regular task is not allowed to run on online&&!active as it would be pushed away quite agressively. We need KTHREAD_IS_PER_CPU to survive in that environment. Therefore set the affinity after getting that magic flag.
Showing the changes to kernel/workqueue.c (1 of 1 file). Show all
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| @@ -1848,12 +1848,6 @@ static void worker_attach_to_pool(struct worker *worker, · 1847 unmodified lines | ||
| 1848 | 1848 | { |
| 1849 | 1849 | mutex_lock(&wq_pool_attach_mutex); |
| 1850 | 1850 | |
| 1851 | − /* | |
| 1852 | − * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any | |
| 1853 | − * online CPUs. It'll be re-applied when any of the CPUs come up. | |
| 1854 | − */ | |
| 1855 | − set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); | |
| 1856 | − | |
| 1857 | 1851 | /* |
| 1858 | 1852 | * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains |
| 1859 | 1853 | * stable across this function. See the comments above the flag |
| @@ -1864,6 +1858,9 @@ static void worker_attach_to_pool(struct worker *worker, · 4 unmodified lines | ||
| 1864 | 1858 | else |
| 1865 | 1859 | kthread_set_per_cpu(worker->task, pool->cpu); |
| 1866 | 1860 | |
| 1861 | + if (worker->rescue_wq) | |
| 1862 | + set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); | |
| 1863 | + | |
| 1867 | 1864 | list_add_tail(&worker->node, &pool->workers); |
| 1868 | 1865 | worker->pool = pool; |
| 1869 | 1866 | |