diff options
Diffstat (limited to 'Master/tlpkg/tlperl/lib/pods/perlfork.pod')
-rw-r--r-- | Master/tlpkg/tlperl/lib/pods/perlfork.pod | 50 |
1 files changed, 38 insertions, 12 deletions
diff --git a/Master/tlpkg/tlperl/lib/pods/perlfork.pod b/Master/tlpkg/tlperl/lib/pods/perlfork.pod index 48d65ed4c58..709d053d28e 100644 --- a/Master/tlpkg/tlperl/lib/pods/perlfork.pod +++ b/Master/tlpkg/tlperl/lib/pods/perlfork.pod @@ -37,7 +37,7 @@ thread that implements this child "process" as the pseudo-process. To the Perl program that called fork(), all this is designed to be transparent. The parent returns from the fork() with a pseudo-process -ID that can be subsequently used in any process manipulation functions; +ID that can be subsequently used in any process-manipulation functions; the child returns from the fork() with a value of C<0> to signify that it is the child pseudo-process. @@ -77,12 +77,24 @@ and return its status. =item kill() -kill() can be used to terminate a pseudo-process by passing it the ID returned -by fork(). This should not be used except under dire circumstances, because -the operating system may not guarantee integrity of the process resources -when a running thread is terminated. Note that using kill() on a -pseudo-process() may typically cause memory leaks, because the thread that -implements the pseudo-process does not get a chance to clean up its resources. +C<kill('KILL', ...)> can be used to terminate a pseudo-process by +passing it the ID returned by fork(). This should not be used except +under dire circumstances, because the operating system may not +guarantee integrity of the process resources when a running thread is +terminated. Note that using C<kill('KILL', ...)> on a +pseudo-process() may typically cause memory leaks, because the thread +that implements the pseudo-process does not get a chance to clean up +its resources. + +C<kill('TERM', ...)> can also be used on pseudo-processes, but the +signal will not be delivered while the pseudo-process is blocked by a +system call, e.g. waiting for a socket to connect, or trying to read +from a socket with no data available. Starting in Perl 5.14 the +parent process will not wait for children to exit once they have been +signalled with C<kill('TERM', ...)> to avoid deadlock during process +exit. You will have to explicitly call waitpid() to make sure the +child has time to clean-up itself, but you are then also responsible +that the child is not blocking on I/O either. =item exec() @@ -137,11 +149,12 @@ to complete before they exit. This means that the parent and every pseudo-child created by it that is also a pseudo-parent will only exit after their pseudo-children have exited. -A way to mark a pseudo-processes as running detached from their parent (so -that the parent would not have to wait() for them if it doesn't want to) -will be provided in future. +Starting with Perl 5.14 a parent will not wait() automatically +for any child that has been signalled with C<sig('TERM', ...)> +to avoid a deadlock in case the child is blocking on I/O and +never receives the signal. -=head2 CAVEATS AND LIMITATIONS +=head1 CAVEATS AND LIMITATIONS =over 8 @@ -184,9 +197,22 @@ On some operating systems, notably Solaris and Unixware, calling C<exit()> from a child process will flush and close open filehandles in the parent, thereby corrupting the filehandles. On these systems, calling C<_exit()> is suggested instead. C<_exit()> is available in Perl through the -C<POSIX> module. Please consult your systems manpages for more information +C<POSIX> module. Please consult your system's manpages for more information on this. +=item Open directory handles + +Perl will completely read from all open directory handles until they +reach the end of the stream. It will then seekdir() back to the +original location and all future readdir() requests will be fulfilled +from the cache buffer. That means that neither the directory handle held +by the parent process nor the one held by the child process will see +any changes made to the directory after the fork() call. + +Note that rewinddir() has a similar limitation on Windows and will not +force readdir() to read the directory again either. Only a newly +opened directory handle will reflect changes to the directory. + =item Forking pipe open() not yet implemented The C<open(FOO, "|-")> and C<open(BAR, "-|")> constructs are not yet |