Re: [9fans] create/create race

["G. David Butler" <gdb@dbSystems.com>]

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Wow, this is a sore subject. Check the archives of this list for a long version of this discussion.

David

Sent from my phone. Please excuse misspellings and terseness.


> On Nov 30, 2016, at 5:04 AM, Giacomo Tesio <giacomo@tesio.it> wrote:
> 
> Hi guys, I know this is a noob question, but I'd really like to understand this aspect of the kernel design.
> 
> I'm planning to experiment on the topic, modifying chan.c so that the semantics of create(2) match those of create(5) about existing files. I guess that the number of callers to fix is manageable.
> 
> But since I can't see any good reason for the race being there in the first place (except maybe backward compatibility with unix, but that was not a problem for Plan 9 designers), I'm pretty sure I'm missing something obvious.
> 
> 
> So, please, do you know why the create syscall does not simply return an error if the file already exists?
> You might save me a few headache... 
> 
> 
> Thanks for your help!
> 
> 
> Giacomo
> 
> 
> 
> 2016-05-24 23:25 GMT+02:00 Giacomo Tesio <giacomo@tesio.it>:
>> I'm pretty curious about the create(2)/create(5) race described in a comment in namec (see https://github.com/brho/plan9/blob/master/sys/src/9/port/chan.c#L1564-L1603)
>> 
>> Does anyone know or remember the reasoning behind this design?
>> 
>> What was wrong about using the create(5) semantics for the create(2) syscall?
>> 
>> 
>> Giacomo
> 

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