Subject: Re: file descriptor races
To: =?iso-8859-1?Q?Jarom=EDr_Dolecek?= <email@example.com>
From: Jason R Thorpe <firstname.lastname@example.org>
Date: 06/06/2001 16:07:10
On Tue, Jun 05, 2001 at 12:16:57PM +0200, Jaromír Dolecek wrote:
> FreeBSD seem to adopt something called fdrop(), which seems to drop
> all references to given file. I'd much rather introduce something
> like 'atomic falloc'. The proposed interface
fdrop() is not for that, at all. fdrop() is sort of like our FILE_UNUSE(),
except they don't deal with the "no, the file descriptor is being closed"
> fallocm(struct proc *p, struct file *resultfp, int resultfd, int nelem)
> i.e. the function gets passed 'struct file *' array and int array with size
> of 'nelem', and would take care to allocate either nelem descriptors,
> or fail and not allocate either (i.e. free those allocated so far, before
> it would return to caller). The most simple way to provide 'atomicity'
> would be probably to introduce e.g. special FIF_NOTREADY flag,
> which sys_dup(), sys_fcntl(), sys_read(), sys_readv(), sys_write(),
> sys_writev(), sys_close() would check and return EBADF if it's set.
> Or, optionally, we may use FIF_WANTCLOSE | FIF_NOTREADY, and only
> change sys_close() to check for FIF_NOTREADY flag (the others
> already check the FIF_WANTCLOSE flag).
Yah, this might not be a bad idea, though I prefer FIF_LARVAL to NOTREADY :-)
Since I'm already in this code up to my elbows, I'll work on it.
-- Jason R. Thorpe <email@example.com>