Hi, thanks for your thorough review. On Sun, Jul 03, 2011 at 12:34:22AM +0200, Samuel Thibault wrote: > Jeremie Koenig, le Wed 29 Jun 2011 18:30:16 +0200, a écrit : > > * hurd/hurdsig.c (check_pending_signals): Split into pending_signals, > > post_pending and post_all_pending_signals. > > (_hurd_internal_post_signal): Handle the distinction between poll > > requests and real signals there. > > I believe it is correct. > > There is just one change that would be worth mentioning in the changelog: > > > - /* We "deliver" immediately pending blocked signals whose > > - action might be to ignore, so that if ignored they are > > - dropped right away. */ > > - || ss->actions[signo].sa_handler == SIG_IGN > > - || ss->actions[signo].sa_handler == SIG_DFL)) > > This is not done any more. Actually I believe it is more correct.
I don't think POSIX has a strong requirement either way. For instance, (http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html) | If the action associated with a blocked signal is anything other than to | ignore the signal, and if that signal is generated for the thread, the | signal shall remain pending until it is unblocked, it is accepted when | it is selected and returned by a call to the sigwait() function, or the | action associated with it is set to ignore the signal. (http://pubs.opengroup.org/onlinepubs/009604499/xrat/xsh_chap02.html) | In the 4.3 BSD system, signals that are blocked and set to SIG_IGN are | discarded immediately upon generation. For a signal that is ignored as | its default action, if the action is SIG_DFL and the signal is blocked, | a generated signal remains pending. In the 4.1 BSD system and in System | V Release 3 (two other implementations that support a somewhat similar | signal mechanism), all ignored blocked signals remain pending if | generated. Because it is not normally useful for an application to | simultaneously ignore and block the same signal, it was unnecessary for | POSIX.1 to specify behavior that would invalidate any of the historical | implementations. > For instance, I believe that the following > > signal(SIGINT, SIG_IGN); > sighold(SIGINT); > raise(SIGINT); > signal(SIGINT, SIG_DFL); > sigrelse(SIGINT); > printf("foo\n"); > > is indeed supposed to terminate on sigrelse() (and it does on Linux), > and not ignore the signal just because the handler is currently SIGIGN. > It can indeed be useful to be able to block the signal while twiddling > with the signal handler. Note that this example still does not terminate after the patch, because ignored signals are never actually marked pending: (hurd/hurdsig.c) | /* Handle receipt of a blocked signal, or any signal while stopped. */ | if (act != ignore && /* Signals ignored now are forgotten now. */ | __sigismember (&ss->blocked, signo) || | (signo != SIGKILL && _hurd_stopped)) | { | mark_pending (); | act = ignore; | } The removed code changed anything only if a previously effectful, blocked signal has been marked pending, then reset to SIG_IGN (or a benign SIG_DFL) in the meantime. If a poll request happens, the signal will merely be given a new opportunity to be forgotten. So the patch probably changes behaviour only in corner cases, if at all. -- Jeremie Koenig <j...@jk.fr.eu.org> http://jk.fr.eu.org
