signal.c File Reference

Signal handling functions. More...

#include <signal.h>
#include <sys/types.h>
#include <regex.h>
#include "para.h"
#include "error.h"
#include "fd.h"
#include "list.h"
#include "string.h"
#include "sched.h"

Functions
struct signal_task *	signal_init_or_die (void)
	Initialize the paraslash signal subsystem. More...
int	para_reap_child (pid_t *pid)
	Reap one child. More...
void	para_sigaction (int sig, void(*handler)(int))
	Install the given handler for the given signal. More...
void	para_install_sighandler (int sig)
	Install the generic signal handler for the given signal number. More...
void	para_block_signal (int sig)
	Block a signal for the caller. More...
void	para_unblock_signal (int sig)
	Unblock a signal. More...
int	para_next_signal (void)
	Return the number of the next pending signal. More...
void	signal_shutdown (struct signal_task *st)
	Close the write end of the signal pipe, deallocate resources. More...

Detailed Description

Signal handling functions.

Function Documentation

signal_init_or_die()

struct signal_task* signal_init_or_die

(

void

)

Initialize the paraslash signal subsystem.

This function creates a pipe, the signal pipe, to deliver pending signals to the application (Bernstein's trick). It should be called during the application's startup part, followed by subsequent calls to para_install_sighandler() for each signal that should be caught.

A generic signal handler is used for all signals simultaneously. When a signal arrives, the signal handler writes the number of the signal received to one end of the signal pipe. The application can test for pending signals by checking if the file descriptor of the other end of the signal pipe is ready for reading.

Returns

This function either succeeds or calls exit(3) to terminate the current process. On success, a signal task structure is returned.

References PARA_NOTICE_LOG.

para_reap_child()

int para_reap_child

(

pid_t *

pid

)

Reap one child.

Parameters

pid	In case a child died, its pid is returned here.

Call waitpid() and print a log message containing the pid and the cause of the child's death.

Returns

A (negative) paraslash error code on errors, zero, if no child died, one otherwise. If and only if the function returns one, the content of pid is meaningful.

See also

waitpid(2).

References ERRNO_TO_PARA_ERROR, PARA_DEBUG_LOG, and PARA_WARNING_LOG.

para_sigaction()

void para_sigaction	(	int	sig,
		void(*)(int)	handler
	)

Install the given handler for the given signal.

Parameters

sig	The number of the signal to catch.
handler	to be installed, SIG_IGN, or SIG_DFL.

This either succeeds or calls exit(EXIT_FAILURE).

See also

sigaction(2).

References PARA_DEBUG_LOG, and PARA_EMERG_LOG.

Referenced by para_install_sighandler().

para_install_sighandler()

void para_install_sighandler

(

int

sig

)

Install the generic signal handler for the given signal number.

Parameters

sig	The number of the signal to catch.

See also

signal(2), sigaction(2).

References para_sigaction().

para_block_signal()

void para_block_signal

(

int

sig

)

Block a signal for the caller.

Parameters

sig	The signal to block.

This sets the given signal in the current signal mask of the calling process to prevent this signal from delivery.

See also

para_unblock_signal(), sigprocmask(2), sigaddset(3).

References PARA_DEBUG_LOG.

para_unblock_signal()

void para_unblock_signal

(

int

sig

)

Unblock a signal.

Parameters

sig	The signal to unblock.

This function removes the given signal from the current set of blocked signals.

See also

para_block_signal(), sigprocmask(2), sigaddset(3).

References PARA_DEBUG_LOG.

para_next_signal()

int para_next_signal

(

void

)

Return the number of the next pending signal.

Returns

On success, the number of the received signal is returned. If there is no signal currently pending, the function returns zero. On read errors from the signal pipe, the process is terminated.

References read_nonblock().

signal_shutdown()

void signal_shutdown

(

struct signal_task *

st

)

Close the write end of the signal pipe, deallocate resources.

Parameters

st	The pointer obtained earlier from signal_init_or_die().