Messages in this thread | | | Date | Wed, 26 Jul 2000 08:55:17 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] removal of unnecessary irq save/restore in tasklet_hi_schedule |
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On Wed, 26 Jul 2000, Stuart MacDonald wrote: > > > > No, hard-irq's _can_ be re-entered. One hard-irq cannot re-enter itself, > > but you can have _different_ irq's enter each other. As such, to avoid > > deadlock in on the local CPU the current code is needed.. > > So the following is allowable? > > hard_irq_a() { > .. > hard_irq_b(); > .. > }
Yes.
> hard_irq_b() { > .. > hard_irq_a(); > .. > }
Yes.
> Then hard_irq_a has re-entered itself.
No.
Both of the above are allowable, BUT
hard_irq_a() hard_irq_b() hard_irq_a()
is not. We use the interrupt blocking hardware to make sure that as long as irq A is running, further instances of irq A are blocked. OTHER interrupts can still happen.
Linus
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