On Friday 10 October 2008 08:51, dcg wrote: > El Wed, 08 Oct 2008 08:51:51 +0200, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> escribió: > > either dup() the fd or open() the file twice. There is absolutely no > > valid reason to have two threads read from the same fd without > > synchronising their access to it - never. > > In case this is the final consensus, I think that a topic that is brought > to the list every few months and even generates (aparently not neccesary) > patches is a hint that there should be somewhere a commentary (*) like > this: > > (*) I don't know if what I wrote is 100% correct. > > > Signed-off-by: Diego Calleja García <diegocg@xxxxxxxxx> > > Index: 2.6/include/linux/fs.h > =================================================================== > --- 2.6.orig/include/linux/fs.h 2008-10-09 00:06:50.000000000 +0200 > +++ 2.6/include/linux/fs.h 2008-10-09 00:29:03.000000000 +0200 > @@ -821,6 +821,18 @@ > atomic_long_t f_count; > unsigned int f_flags; > mode_t f_mode; > + /* > + * Linux does NOT guarantee atomic reading/writing to file->f_pos in > + * multithread apps running in 32 bit machines. There're several > + * reasons for this behaviour: Note that I don't think we'd want to explicitly guarantee that it is atomic on 64-bit machines either. It does happen to be, but I don't think we want anybody to rely on that... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
