Re: [PATCH] Introduce O_CLOEXEC (take >2)

On Thu, 31 May 2007, Jakub Jelinek wrote:

On Thu, May 31, 2007 at 11:46:31AM -0700, Davide Libenzi wrote:
On Thu, 31 May 2007, Ulrich Drepper wrote:
Davide Libenzi wrote:
Isn't this better be a global process flag? Default should be, for legacy
reasons,

No. Policies are always wrong since it means code that cannot change
the policy (e.g, all runtime libraries) have no access to the
functionality. I cannot set the policy to default to close-on-exit in
glibc all the while the application assumes this is not the case.

I was talking for a broader usage, not only glibc centric. Most ppl
writing MT+exec apps wants all but (eventually) and handfull of files
leaking across the exec boundary.

If open (and all other syscalls that create fds) have O_CLOEXEC (and
something similar for other syscalls), then such a policy can be easily
implemented on the userland, if desired.

That, unless you change all the syscalls creating files to accept new
parameters, would require a syscall+fcntl operation. That is not atomic
(ie, another thread might do exec between the syscall and the fcntl).
Again, mine was a general comment, not directed into magically fixing
existing buggy code. What I meant, was that the vast majority of MT+exec
apps wants all their fds (but an handfull, maybe) to be O_CLOEXEC. So a
global, non-inheritable, per-process flag seemed the most straightforward
solution.



- Davide


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