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Old 19th May 2008
n4uti1us n4uti1us is offline
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Default Spin locks and interrupts disabling

Hi All,

I was looking at the linux kernel, and in the implementation of spinlocks, one can use different functions. One of them is spin_lock_bh(). What it does is it creates a spin lock and disables the software irqs.

In FreeBSD on the other hand, the implementation of spinlocks is done by mtx_lock_spin (which is actually a macro that calls mtx_lock_spin_flags()) but the problem is that is disables all the irq vector (at the bottom of the stack it executes an "cli"). Is there any way one can implement spinlocks that only disable the bottom half (sof irq)?

Alternatively, what would be the best way to manualy disable the soft irqs?

Thank you for reading.
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Old 19th May 2008
J65nko J65nko is offline
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For this rather technical issue you probably will get more response on a FreeBSD mailing list
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Old 20th May 2008
richardpl richardpl is offline
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It was already there - silence was only response.

Use the source, Luke.

I doubt that comparing two kernels is usefull in any way.

Development approach is so different ....


[flame]Just look at Debian[/flame]
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Old 20th May 2008
n4uti1us n4uti1us is offline
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Quote:
Originally Posted by richardpl View Post
It was already there - silence was only response.

Use the source, Luke.

I doubt that comparing two kernels is usefull in any way.

Development approach is so different ....


[flame]Just look at Debian[/flame]
Hi richardpl.

I know the two kernels are fundamentaly different. And it seems like there is no concept of disabling the bottom half in FreeBSD, but I am not 100% sure about it. Have you ever come accros the concept of soft irqs in FreeBSD? If so do you know any way of disabling them?

Again, thank you for your time.
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Old 20th May 2008
richardpl richardpl is offline
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The concept of mutex(9) and linux spinlocks is incompatible with each other. Well I never looked in linux kernel code (only in some drivers ...)

NOTE: I am not kernel developer of any OS, just boring user.
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Old 20th May 2008
n4uti1us n4uti1us is offline
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Bok richardpl!

The fact is that there is some correlation between the functionality (not implementation between the two kernels). But I wanted to go a bit further than that.

Thanks anyway for your help.

If anybody else can give a hand that would be greately appreciated.
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