On 20/12/17(Wed) 15:35, Alexander Bluhm wrote: > On Wed, Dec 20, 2017 at 01:43:13PM +0100, Martin Pieuchot wrote: > > [...] > > Flags are modified by the driver, not by the stack. Some of them are > > event immutable and might be better moved to a different field. > > You have marked if_flags and if_xflags with an [N]. Reading happens > everywhere in the stack. Carp changes them often. I think we have > the kernel lock there. Note that if_flags is short so access is > not atomic. > > Perhaps we should split the flags like I did with the sb_flagsintr > a long time ago. Changing them to int would be an easy first step.
That might be a good thing. That's also why IFF_OACTIVE is no longer a flag. > > The goal is to stop grabbing the lock for per-driver ioctl(2). This > > would fix the problem that sleeping in if_ioctl() might block network > > traffic for a long time. That means the limit between driver and stack > > fields have to be clear. You just pointed out that `if_flags' has some > > issues. > > Thanks for the explanation. The goal sounds reasonable. But that > means we have to check all the drivers and especially the pseudo-drivers' > ioctl functions before unlocking (*ifp->if_ioctl)(). Pseudo-driver would be a second step. We could (ironically) check for IFXF_CLONED and still take the lock for pseudo-drivers.
