… | |
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2108 | |
2108 | |
2109 | When the first watcher gets started will libev actually register something |
2109 | When the first watcher gets started will libev actually register something |
2110 | with the kernel (thus it coexists with your own signal handlers as long as |
2110 | with the kernel (thus it coexists with your own signal handlers as long as |
2111 | you don't register any with libev for the same signal). |
2111 | you don't register any with libev for the same signal). |
2112 | |
2112 | |
2113 | Both the signal mask state (C<sigprocmask>) and the signal handler state |
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2114 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
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2115 | sotpping it again), that is, libev might or might not block the signal, |
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2116 | and might or might not set or restore the installed signal handler. |
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2117 | |
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2118 | If possible and supported, libev will install its handlers with |
2113 | If possible and supported, libev will install its handlers with |
2119 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2114 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2120 | not be unduly interrupted. If you have a problem with system calls getting |
2115 | not be unduly interrupted. If you have a problem with system calls getting |
2121 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2116 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2122 | and unblock them in an C<ev_prepare> watcher. |
2117 | and unblock them in an C<ev_prepare> watcher. |
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2118 | |
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2119 | =head3 The special problem of inheritance over execve |
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2120 | |
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2121 | Both the signal mask (C<sigprocmask>) and the signal disposition |
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2122 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
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2123 | stopping it again), that is, libev might or might not block the signal, |
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2124 | and might or might not set or restore the installed signal handler. |
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2125 | |
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2126 | While this does not matter for the signal disposition (libev never |
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2127 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
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2128 | C<execve>), this matters for the signal mask: many programs do not expect |
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2129 | certain signals to be blocked. |
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2130 | |
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2131 | This means that before calling C<exec> (from the child) you should reset |
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2132 | the signal mask to whatever "default" you expect (all clear is a good |
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2133 | choice usually). |
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2134 | |
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2135 | The simplest way to ensure that the signal mask is reset in the child is |
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2136 | to install a fork handler with C<pthread_atfork> that resets it. That will |
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2137 | catch fork calls done by libraries (such as the libc) as well. |
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2138 | |
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2139 | In current versions of libev, you can also ensure that the signal mask is |
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2140 | not blocking any signals (except temporarily, so thread users watch out) |
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2141 | by specifying the C<EVFLAG_NOSIGNALFD> when creating the event loop. This |
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2142 | is not guaranteed for future versions, however. |
2123 | |
2143 | |
2124 | =head3 Watcher-Specific Functions and Data Members |
2144 | =head3 Watcher-Specific Functions and Data Members |
2125 | |
2145 | |
2126 | =over 4 |
2146 | =over 4 |
2127 | |
2147 | |