Messages in this thread | | | From | Eric Dumazet <> | Subject | Re: [PATCH 2/7] revoke: add f_light flag for struct file | Date | Fri, 9 Mar 2007 12:13:35 +0100 |
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On Friday 09 March 2007 11:43, Pekka Enberg wrote: > On 3/9/07, Eric Dumazet <dada1@cosmosbay.com> wrote: > > Cannot we use a flag in 'struct files_struct', set to one when the task > > is mono-thread (at task creation in fact), and set to 0 when it creates a > > new thread (or when someone remotely access to this "struct > > files_struct" in /proc/pid/fd/... ) > > How does that work? fget_light() has a built-in assumption that as > long as you don't share files_struct, it's okay not to take an extra > reference as current is only one doing close(2) and revoke(2) changes > that. So it's not really about being single-threaded or not.
I just dropped one (silly ?) idea and expected you made the hard work :)
Then just drop the fget_light() 'optimisation' and always take a reference (atomic on f_count) regardless of single-thread or not. Instead of dirtying f_light, just do the straightforward thing and be with it.
(that is : fget_light() = fget() = no more keeping fput_needed everywhere, and convoluted things in some dark sides of the kernel.
It will save some conditional branches and complexity, and you dont need this f_light thing.
> > On 3/9/07, Eric Dumazet <dada1@cosmosbay.com> wrote: > > Also, the thing is racy. > > Aah, fget_light() indeed has a race window between fcheck_files() and > set_f_light().
Yes, you see how hard it is to get this right. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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