Re: sysctl vs /proc/sys

[YOSHIFUJI Hideaki / 吉藤英明]

In article <20031212181517.GM15401@xxxxxxxxxxxxx> (at Fri, 12 Dec 2003 10:15:17 -0800), Mike Fedyk <mfedyk@xxxxxxxxxxxxx> says:

> On Fri, Dec 12, 2003 at 09:28:32AM -0500, James Morris wrote:
> > On Fri, 12 Dec 2003, YOSHIFUJI Hideaki / [iso-2022-jp] 吉藤英明 wrote:
> > 
> > > Can we get the exact previous value from /proc/sys atomicly?
> > 
> > I'm not sure what you mean by this.
> 
> Read value and modify in one op?

Yes, I meant to read old value and to set new one in one system call.
The sysctl system-call does lock_kernel, so sysctl(2) sytem-call 
are serialized.

How about procfs? Are there locks between multiple read-and-write?
Since It seems user-space cannot (or even should not) let kernel 
hold lock(s) during read-and-write operation, procfs cannot be 
the alternative.

Do I mis-understand something?

--yoshfuji
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