On 12/25, Andrey Wagin wrote: > > 2012/12/24 Oleg Nesterov <oleg@xxxxxxxxxx>: > > On 12/24, Andrey Vagin wrote: > >> > >> signalfd should be called with the flag SFD_RAW for that. > >> > >> signalfd_siginfo is not full for siginfo with a negative si_code. > >> copy_siginfo_to_user() is copied a full siginfo to user-space, if > >> si_code is negative. signalfd_copyinfo() doesn't do that and can't be > >> expanded, because it has not compatiable format with siginfo_t. > > > > Yes, but otoh perhaps we should change (fix) signalfd_siginfo/copyinfo, > > its "default" case makes no sense if si_code < 0. > > Its "default" case makes sense if a signal is sent by sigqueue(pid,sig,ptr). But it doesn't really work, that is what I was trying to say. And that is why you want copy_siginfo_to_user ;) > I'm afraid, we can change (fix) signalfd_copyinfo, because for > negative si_code a whole siginfo should be copied to userspace. Exactly, this is what I meant. We simply do not know what this info contains if it was sent by sigqueueinfo(). > Currently if si_code is unknown, signalfd_copyinfo sets only ssi_ptr > and that can't be changed due to backward compatibility. ssi_ptr is in > the midle of signalfd_siginfo and a sizeof(signalfd_siginfo) is equal > to sizeof(siginfo_t). We don't have space to copied siginfo into > signalfd_siginfo. Yes, I understand. > If we want to have another format with SFD_RAW, I prefer to have > siginfo_t instead of signalfd_siginfo. Because if si_code is negative, > it should be siginfo_t in any case. A minor thing is that it can be > sent back without modifications. "without modifications" is not actually true, your patch changes the meaning of ->si_code. Yes, I understand why do you do this, and I am not going to argue. But it looks a bit sad that, say, sigtimedwait() and read(SFD_RAW) will return the "same" siginfo_t except the subtle difference in ->si_code. What I am trying to say, is that SFD_RAW should be named SFD_signalfd_siginfo_SUCKS_BUT_WE_CANT_CHANGE_IT_FOR_COMPATIBILITY ;) So you need another format. And if we add another format we should think twice. For example, if it is _RAW, why we can't simply do memcpy() instead of copy_siginfo_to_user() ? Not that I really suggest this. And if we change the meaning of ->si_code then, perhaps, we should think what else we should change to avoid SFD_RAW_RAW in future. Just for example, we can set MSB in ->si_signo if the signal was private. Oleg. -- 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
