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Re: [RFC PATCH 01/10] sched: core: save IRQ state during locking
- To: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Wed, 24 Feb 2021 18:29:30 +0000
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- Cc: George Dunlap <george.dunlap@xxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>
- Delivery-date: Wed, 24 Feb 2021 18:29:46 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 23/02/2021 02:34, Volodymyr Babchuk wrote:
> With XEN preemption enabled, scheduler functions can be called with
> IRQs disabled (for example, at end of IRQ handler), so we should
> save and restore IRQ state in schedulers code.
>
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
These functions need to fixed not to be _irq() variants in the first place.
The only reason they're like that is so the schedule softirq/irq can
edit the runqueues. I seem to recall Dario having a plan to switch the
runqueues to using a lockless update mechanism, which IIRC removes any
need for any of the scheduler locks to be irqs-off.
~Andrew
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