On Fri, Jun 01 2007, H. Peter Anvin wrote: > > So there's a few things to take away from this: > > > > - regular file access MUST NOT return EAGAIN just because a page isn't > > in the cache. Doing so is simply a bug. No ifs, buts or maybe's about > > it! > > > > Busy-looping is NOT ACCEPTABLE! > > > > - you *could* make some alternative conventions: > > > > (a) you could make O_NONBLOCK mean that you'll at least > > guarantee that you *start* the IO, and while you never return > > EAGAIN, you migth validly return a _partial_ result! > > > > (b) variation on (a): it's ok to return EAGAIN if _you_ were the > > one who started the IO during this particular time aroudn the > > loop. But if you find a page that isn't up-to-date yet, and > > you didn't start the IO, you *must* wait for it, so that you > > end up returning EAGAIN atmost once! Exactly because > > busy-looping is simply not acceptable behaviour! > > (b) seems really ugly. (a) is at least well-defined. Either seems > wrong, though.
I totally agree, b) would get nasty. And while a) isn't perfect by any means, I do follow Linus' logic and agree it's probably the best (only?) way to handle it. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
