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authorPeter Zijlstra <peterz@infradead.org>2021-01-12 11:24:04 +0100
committerPeter Zijlstra <peterz@infradead.org>2021-01-22 15:09:42 +0100
commitac687e6e8c26181a33270efd1a2e2241377924b0 (patch)
tree2409cb957d209a81666ccd573f8d64def03a8ff4 /kernel/smpboot.c
parent22f667c97aadbf481e2cae2d6feabdf431e27b31 (diff)
kthread: Extract KTHREAD_IS_PER_CPU
There is a need to distinguish geniune per-cpu kthreads from kthreads that happen to have a single CPU affinity. Geniune per-cpu kthreads are kthreads that are CPU affine for correctness, these will obviously have PF_KTHREAD set, but must also have PF_NO_SETAFFINITY set, lest userspace modify their affinity and ruins things. However, these two things are not sufficient, PF_NO_SETAFFINITY is also set on other tasks that have their affinities controlled through other means, like for instance workqueues. Therefore another bit is needed; it turns out kthread_create_per_cpu() already has such a bit: KTHREAD_IS_PER_CPU, which is used to make kthread_park()/kthread_unpark() work correctly. Expose this flag and remove the implicit setting of it from kthread_create_on_cpu(); the io_uring usage of it seems dubious at best. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210121103506.557620262@infradead.org
Diffstat (limited to 'kernel/smpboot.c')
-rw-r--r--kernel/smpboot.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index 2efe1e206167..f25208e8df83 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -188,6 +188,7 @@ __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
kfree(td);
return PTR_ERR(tsk);
}
+ kthread_set_per_cpu(tsk, cpu);
/*
* Park the thread so that it could start right on the CPU
* when it is available.