Messages in this thread | | | Date | Mon, 10 Dec 2012 10:40:05 +0000 | From | James Hogan <> | Subject | Re: [braindump][RFC] signals and syscall restarts (Re: [PATCH v2 19/44] metag: Signal handling) |
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On 06/12/12 22:09, Al Viro wrote: > On Thu, Dec 06, 2012 at 11:17:34AM +0000, James Hogan wrote: > >> Agreed, it looks wrong. Looking at the sh version, is there a particular >> reason to only check for -EFAULT and not the other errors that >> do_sigaltstack can return (-EPERM, -EINVAL, and -ENOMEM)? > > See commit fae2ae2a900a5c7bb385fe4075f343e7e2d5daa2
Thanks :)
> >>> BTW, what's to stop the syscall restart triggering if you catch a signal >>> while in rt_sigreturn(2)? >> >> I'm not sure I understand how that could cause a problem. Could you >> elaborate the sequence of events? >> >> The signal restart is triggered by the return value register, so >> rt_sigreturn would have to return -ERESTART*. This could happen if the >> signal handler overwrote the return value in the sigcontext (which as >> far as I can tell could also happen on ARM), or if the syscall that was >> originally interrupted by the signal has -ERESTARTNOINTR || >> (-ERESTARTSYS && SA_RESTART), but in that case rt_sigreturn has already >> switched back to the context of the original syscall so that's the right >> thing to do isn't it? I've probably missed something important :-) > > [we probably need something along the lines of braindump below in > somewhere in Documentation/*; comments and improvements are very > welcome - this is just a starting point. We *do* need some coherent > explanation of signal semantics, judging by how often people step on > the same landmines...]
Thanks, this helps a lot.
Cheers James
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