Messages in this thread |  | | Subject | Re: [RFC] I still see people using cli() | From | (Eric W. Biederman) | Date | 08 Oct 2001 09:11:57 -0600 |
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Victor Yodaiken <yodaiken@fsmlabs.com> writes:
> On Mon, Oct 08, 2001 at 07:59:05PM +0530, BALBIR SINGH wrote: > > BTW, that brings me to another issue, once the kernel becomes preemptibel, > what > > > are the locking issues? how are semaphores and spin-locks affected? Has > anybody > > > defined or come up with the rules/document yet? > > IF the kernel becomes preemptible it will be so slow, so buggy, and so painful > to maintain, that those issues won't matter.
The preemptible kernel work just takes the current SMP code, and allows it to work on a single processor. You are not interruptted if you have a lock held. This makes the number of cases in the kernel simpler, and should improve maintenance as more people will be affected by the SMP issues.
Right now there is a preemptible kernel patch being maintained somewhere. I haven't had a chance to look recently. But the recent threads on low latency mentioned it.
As for rules. They are the usual SMP rules. In earlier version there was a requirement or that you used balanced constructs.
i.e. spin_lock_irqsave ... spin_unlock_irqrestore
and not.
spin_lock_irqsave ... spin_unlock .. restore_flags.
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