On Tue, Sep 27, 2011 at 5:40 PM, Jeff Haran <jharan@xxxxxxxxxxxxxx> wrote:
From: kernelnewbies-bounces@xxxxxxxxxxxxxxxxx
[mailto:kernelnewbies-bounces@xxxxxxxxxxxxxxxxx] On Behalf Of Venkatram
Tummala
Sent: Tuesday, September 27, 2011 5:31 PM
To: Mulyadi Santosa
Cc: kernelnewbies
Subject: Re: Prevent a process from opening a file more than once
When you say "I need to prevent a process from opening the file more
On Tue, Sep 27, 2011 at 5:22 PM, Mulyadi Santosa
<mulyadi.santosa@xxxxxxxxx> wrote:
Hi :)
On Wed, Sep 28, 2011 at 06:56, Venkatram Tummala
<venkatram867@xxxxxxxxx> wrote:
> Hi All,
> I have a simple device driver which creates a /dev/XYZ file. I need to
> prevent a process from opening the file more than once. However,
multiple
> processes can open the file simultaneously. Is there any any elegant
way to
> do this other than checking all opened files in the process ?
Uhm, keep a reference count and increment it on every file open in
your module? How does that sound?
Well, which refcount should i use? I can't use the refcount in the file
object as the file objects passed to me are different each time the file
is opened in the process.
than once.", do you mean a single process opening the file, closing it
and then opening it again would be disallowed?
No. If the file is already opened in the process, the process shouldn't be allowed to open the file again. It is fine if the process opens, closes & then opens the file again.
Or do you mean that a
single process opening the file, keeping it open and then opening it
again under another fd would be disallowed?
Yes, this is what i am looking for.
How about multiple threads within the same process? Are they treated as
the same process by these rules?
Yes. Threads are treated as the same process. So, if one thread has the file already opened, another thread in the same process shouldn't be able to open it.
Venkat
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