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Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall |
Date: |
Wed, 6 May 2009 11:53:37 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Martin Mohring wrote:
> >> The point of pipe2() with FD_CLOEXEC is to be atomic: make sure
> >> another thread can never see the file descriptor with FD_CLOEXEC not set.
> >
> How do we want to handle if "O_CLOEXEC" is not defined on the host OS,
> because kernel too old (Debian Etch, CentOS 5)? Should it then return
> ENOSYS?
You can emulate it on any host OS using a mutex or read-write lock:
- Acquire the lock for reading before calling the hosts's
open/pipe/socket/etc.
- Release the lock after calling the host's fcntl to set FD_CLOEXEC.
- Acquire the lock for writing around emulation of fork, exec,
clone and unshare.
There are ways to do it more efficiently without a lock, but I don't
think they are worth bothering with here.
-- Jamie
- [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Riku Voipio, 2009/05/05
- [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall [v2], Riku Voipio, 2009/05/05
- Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Jamie Lokier, 2009/05/05
- Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Riku Voipio, 2009/05/06
- Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Jamie Lokier, 2009/05/06
- Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Riku Voipio, 2009/05/06
- Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Martin Mohring, 2009/05/06
- Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Paul Brook, 2009/05/06
- Re: [Qemu-devel] [PATCH] linux-user: implement pipe2 syscall, Riku Voipio, 2009/05/06