On Mon, 30 Jul 2007, Andrew Morton wrote: > On Mon, 30 Jul 2007 19:09:38 +0200 > Michael Buesch <mb@xxxxxxxxx> wrote: > > > On Monday 30 July 2007, Satyam Sharma wrote: > > > > > > On Mon, 30 Jul 2007, Michael Buesch wrote: > > > > > > > On Sunday 29 July 2007 23:34, Matthias Kaehlcke wrote: > > > > > > > > > > @@ -902,7 +902,7 @@ static int hfa384x_set_rid(struct net_device *dev, u16 rid, void *buf, int len) > > > > > /* RID len in words and +1 for rec.rid */ > > > > > rec.len = cpu_to_le16(len / 2 + len % 2 + 1); > > > > > > > > > > - res = down_interruptible(&local->rid_bap_sem); > > > > > + res = mutex_lock_interruptible(&local->rid_bap_mtx); > > > > > if (res) > > > > > return res; > > > > > > > > > > > > > Is res returned to userspace? If yes, that's not right. > > > > > > Yup, that's not right. > > > > > > > On a interrupted mutex allocation you should return > > > > -ERESTARTSYS to userspace. > > > > > > Nope, userspace must not see ERESTARTSYS (I /think/ this is the third > > > time I'm participating in this exact same discussion :-) > > > > > > If the return would be caught by a previous in-kernel caller in the > > > call chain, ERESTARTSYS is okay and it could try to restart the > > > operation. However, if the return goes unfiltered directly to > > > userspace, EINTR is the correct choice. > > > > Last time I submitted a patch which returned EINTR to userspace, > > people came and said it was wrong. It was said that we must > > return ERESTARTSYS to the libc and the libc will convert that > > into either EINTR or automatically restart it immediately. > > (You can set that in the sigaction stuff). > > > > So either the one who told me that last time was wrong, or you. :) > > > > Andrew? I think you were involved in this discussion I mentioned. > > (It was about the HW-RNG chardev, but that doesn't matter here). > > who, me? signals? Danger. > > yes, I think ERESTARTSYS is correct. That gets converted to -EINTR by the > arch's signal handling code (not by glibc) just before we return to > userspace. Hmm? But the question is whether which of EINTR or ERESTARTSYS is correct to be returned to userspace (so, EINTR). But now that you pointed to the automagic ERESTARTSYS-to-EINTR conversion in the arch/ code, I think there's no problem returning ERESTARTSYS from syscalls in generic kernel code when interrupted by a signal either (if all arch's do that conversion). Probably makes sense to change down_interruptible() and mutex_lock_interruptible() to return ERESTARTSYS (and not EINTR) in that case. wait_event_interruptible() is already ERESTARTSYS, I see ... Satyam - To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
