sched: membarrier: cover kthread_use_mm (v4)

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Add comments and memory barrier to kthread_use_mm and kthread_unuse_mm
to allow the effect of membarrier(2) to apply to kthreads accessing
user-space memory as well.

Given that no prior kthread use this guarantee and that it only affects
kthreads, adding this guarantee does not affect user-space ABI.

Refine the check in membarrier_global_expedited to exclude runqueues
running the idle thread rather than all kthreads from the IPI cpumask.

Now that membarrier_global_expedited can IPI kthreads, the scheduler
also needs to update the runqueue's membarrier_state when entering lazy
TLB state.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201020134715.13909-3-mathieu.desnoyers@efficios.com

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This commit is contained in:

Mathieu Desnoyers 2020-10-20 09:47:14 -04:00 • committed by Peter Zijlstra

parent 5bc7850232

commit 618758ed3a

3 changed files with 25 additions and 4 deletions

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21

kernel/kthread.c

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1

kernel/sched/idle.c

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7

kernel/sched/membarrier.c

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