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This commit is contained in:
Yaroslav Tykhiy 2004-06-07 21:48:02 +00:00
parent aa57bb0424
commit cacc8e6c5d
1 changed files with 16 additions and 10 deletions
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26
lib/libc/sys/sigaction.2
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@ -65,7 +65,8 @@ struct sigaction {
The system defines a set of signals that may be delivered to a process.
Signal delivery resembles the occurrence of a hardware interrupt:
the signal is normally blocked from further occurrence, the current process
context is saved, and a new one is built. A process may specify a
context is saved, and a new one is built.
A process may specify a
.Em handler
to which a signal is delivered, or specify that a signal is to be
.Em ignored .
@ -78,7 +79,8 @@ in which case its delivery is postponed until it is
The action to be taken on delivery is determined at the time
of delivery.
Normally, signal handlers execute on the current stack
of the process. This may be changed, on a per-handler basis,
of the process.
This may be changed, on a per-handler basis,
so that signals are taken on a special
.Em "signal stack" .
.Pp
@ -89,9 +91,10 @@ but other signals may yet occur.
A global
.Em "signal mask"
defines the set of signals currently blocked from delivery
to a process. The signal mask for a process is initialized
from that of its parent (normally empty). It
may be changed with a
to a process.
The signal mask for a process is initialized
from that of its parent (normally empty).
It may be changed with a
.Xr sigprocmask 2
call, or when a signal is delivered to the process.
.Pp
@ -114,7 +117,8 @@ system call.
When a caught signal
is delivered, the current state of the process is saved,
a new signal mask is calculated (as described below),
and the signal handler is invoked. The call to the handler
and the signal handler is invoked.
The call to the handler
is arranged so that if the signal handling routine returns
normally the process will resume execution in the context
from before the signal's delivery.
@ -195,8 +199,8 @@ If this bit is set when calling
for the
.Dv SIGCHLD
signal, the system will not create zombie processes when children of
the calling process exit. If the calling process subsequently issues
a
the calling process exit.
If the calling process subsequently issues a
.Xr wait 2
(or equivalent), it blocks until all of the calling process's child
processes terminate, and then returns a value of \-1 with
@ -452,7 +456,8 @@ Extension Interfaces:
.Fn strlcat .
.Pp
All functions not in the above lists are considered to be unsafe
with respect to signals. That is to say, the behaviour of such
with respect to signals.
That is to say, the behaviour of such
functions when called from a signal handler is undefined.
In general though, signal handlers should do little more than set a
flag; most other actions are not safe.
@ -628,7 +633,8 @@ The
and
.Dv SA_RESETHAND
flags are intended for backwards compatibility with other operating
systems. The
systems.
The
.Dv SA_NOCLDSTOP ,
and
.Dv SA_NOCLDWAIT