On Sat, Feb 04, 2017 at 07:19:37AM -0800, Eric Dumazet wrote: > > > The comment says that it's pairing with an mb in tcp_poll, but > > tcp_poll doesn't touch QUEUE_SHRUNK at all. So what exactly is > > this barrier for? > > Do not focus on QUEUE_SHRUNK flag, which is locally used by this thread > only. > > The confusion comes because 3c7151275c0c9a80c3375f9874b1c7129a105eea > thought it could avoid the cost of smp_mb() by abusing the fact that > sock_reset_flag(sk, SOCK_QUEUE_SHRUNK) was doing an atomic, > but it was not.
Thanks for the explanation. I see what it's protecting now. And this could indeed be responsible for the race that Oleg reported. -- Email: Herbert Xu <herb...@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
