diff options
| -rw-r--r-- | Changes | 7 | ||||
| -rw-r--r-- | ev.c | 11 | ||||
| -rw-r--r-- | ev.h | 3 | ||||
| -rw-r--r-- | ev.pod | 30 |
4 files changed, 33 insertions, 18 deletions
@@ -1,6 +1,10 @@ Revision history for libev, a high-performance and full-featured event loop. -TODO: somehow unblock procmask? + - signalfd is no longer used by default and has to be requested + explicitly - this means that easy to catch bugs become hard to + catch race conditions, but the users have spoken. + - point out the unspecified signal mask in the documentation, and + that this is a race condition regardless of EV_SIGNALFD. - backport inotify code to C89. - inotify file descriptors could leak into child processes. - ev_stat watchers could keep an errornous extra ref on the loop, @@ -10,7 +14,6 @@ TODO: somehow unblock procmask? symbols to make it easier for apps to do their own fd management. - support EV_IDLE_ENABLE being disabled in ev++.h (patch by Didier Spezia). - - point out the unspecified signal mask in the documentation. - take advantage of inotify_init1, if available, to set cloexec/nonblock on fd creation, to avoid races. - the signal handling pipe wasn't always initialised under windows @@ -1607,7 +1607,7 @@ loop_init (EV_P_ unsigned int flags) fs_fd = flags & EVFLAG_NOINOTIFY ? -1 : -2; #endif #if EV_USE_SIGNALFD - sigfd = flags & EVFLAG_NOSIGFD ? -1 : -2; + sigfd = flags & EVFLAG_SIGNALFD ? -2 : -1; #endif if (!(flags & 0x0000ffffU)) @@ -2792,11 +2792,14 @@ ev_signal_stop (EV_P_ ev_signal *w) #if EV_USE_SIGNALFD if (sigfd >= 0) { - sigprocmask (SIG_UNBLOCK, &sigfd_set, 0);//D + sigset_t ss; + + sigemptyset (&ss); + sigaddset (&ss, w->signum); sigdelset (&sigfd_set, w->signum); + signalfd (sigfd, &sigfd_set, 0); - sigprocmask (SIG_BLOCK, &sigfd_set, 0);//D - /*TODO: maybe unblock signal? */ + sigprocmask (SIG_UNBLOCK, &ss, 0); } else #endif @@ -406,7 +406,8 @@ union ev_any_watcher #define EVFLAG_FORKCHECK 0x02000000U /* check for a fork in each iteration */ /* debugging/feature disable */ #define EVFLAG_NOINOTIFY 0x00100000U /* do not attempt to use inotify */ -#define EVFLAG_NOSIGFD 0x00200000U /* do not attempt to use signalfd */ +#define EVFLAG_NOSIGFD 0 /* compatibility to pre-3.9 */ +#define EVFLAG_SIGNALFD 0x00200000U /* attempt to use signalfd */ /* method bits to be ored together */ #define EVBACKEND_SELECT 0x00000001U /* about anywhere */ #define EVBACKEND_POLL 0x00000002U /* !win */ @@ -372,13 +372,16 @@ I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and testing, this flag can be useful to conserve inotify file descriptors, as otherwise each loop using C<ev_stat> watchers consumes one inotify handle. -=item C<EVFLAG_NOSIGFD> +=item C<EVFLAG_SIGNALFD> -When this flag is specified, then libev will not attempt to use the -I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is -probably only useful to work around any bugs in libev. Consequently, this -flag might go away once the signalfd functionality is considered stable, -so it's useful mostly in environment variables and not in program code. +When this flag is specified, then libev will attempt to use the +I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API +delivers signals synchronously, which makes is both faster and might make +it possible to get the queued signal data. + +Signalfd will not be used by default as this changes your signal mask, and +there are a lot of shoddy libraries and programs (glib's threadpool for +example) that can't properly initialise their signal masks. =item C<EVBACKEND_SELECT> (value 1, portable select backend) @@ -2134,7 +2137,7 @@ not be unduly interrupted. If you have a problem with system calls getting interrupted by signals you can block all signals in an C<ev_check> watcher and unblock them in an C<ev_prepare> watcher. -=head3 The special problem of inheritance over execve +=head3 The special problem of inheritance over fork/execve/pthread_create Both the signal mask (C<sigprocmask>) and the signal disposition (C<sigaction>) are unspecified after starting a signal watcher (and after @@ -2154,10 +2157,15 @@ The simplest way to ensure that the signal mask is reset in the child is to install a fork handler with C<pthread_atfork> that resets it. That will catch fork calls done by libraries (such as the libc) as well. -In current versions of libev, you can also ensure that the signal mask is -not blocking any signals (except temporarily, so thread users watch out) -by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This -is not guaranteed for future versions, however. +In current versions of libev, the signal will not be blocked indefinitely +unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces +the window of opportunity for problems, it will not go away, as libev +I<has> to modify the signal mask, at least temporarily. + +So I can't stress this enough I<if you do not reset your signal mask +when you expect it to be empty, you have a race condition in your +program>. This is not a libev-specific thing, this is true for most event +libraries. =head3 Watcher-Specific Functions and Data Members |