Messages in this thread | | | Date | Thu, 25 Jun 2009 19:04:04 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [PATCH] net: fix race in the receive/select |
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On Fri, 26 Jun 2009, Eric Dumazet wrote:
> Davide Libenzi a écrit : > > On Thu, 25 Jun 2009, Oleg Nesterov wrote: > > > >> Can't really comment this patch, except this all looks reasonable to me. > >> Add more CCs. > > > > While this can work, IMO it'd be cleaner to have the smp_mb() moved from > > fs/select.c to the ->poll() function. > > Having a barrier that matches another one in another susbsystem, because > > of the special locking logic of such subsystem, is not too shiny IMHO. > > > > Yes but barrier is necessary only if add_wait_queue() was actually called, and __pollwait() > does this call. > > Adding a plain smp_mb() in tcp_poll() for example would slowdown select()/poll() with NULL > timeout.
Do you think of it as good design adding an MB on a subsystem, because of the special locking logic of another one? The (eventual) slowdown, IMO can be argued sideways, by saying that non-socket users will pay the price for their polls.
- Davide
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