_signotifywait(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | NOTES

NAME

_signotifywait, _lwp_sigredirect- deliver process signals to specific LWPs

SYNOPSIS

#include <sys/lwp.h>

int _signotifywait(void);
int _lwp_sigredirect(lwpid_t target_lwp, int signo , int *queued);

DESCRIPTION

In a multithreaded process, signals that are generated for a process are delivered to one of the threads that does not have that signal masked. If all of the application threads are masking that signal, its delivery waits until one of them unmasks it.

The disposition of the each thread's signal mask is unknown to the kernel when it generates signals for the process. The _signotifywait() and _lwp_sigredirect() functions provide a mechanism to direct instances of signals generated for the process to application-specified LWPs. Each process has a set of signals pending for the process, and for each LWP there is a set of signals pending for that LWP. If no signals are pending, these sets are empty.

There is also a process-wide signal set, termed the notification set, manipulated by these functions. A signal generated for the process where the signal number is not in the notification set is called an unnotified signal.

In a multithreaded program there is an aslwp , a special LWP endowed with powers to handle signals that are generated for a process. The _signotifywait() function is used to await signals generated for the process, and should be called only from the aslwp . In general, these functions are not to be called from the application-level.

If there is a pending unnotified signal when _signotifywait() is called, that signal is selected and the call returns immediately. If there is not a signal pending, the call suspends the calling LWP until the generation of an unnotified signal; that signal then is selected and the function returns. In both cases, the selected signal number is set in the notification set and returned as the value of _signotifywait() . The signal remains pending for the process, and any associated siginfo(3HEAD) information remains queued at the process.

The _lwp_sigredirect() function requests that a signal pending for the process be delivered to the LWP specified by target_lwp . If target_lwp is 0 , the signal is discarded. It is an error if signo is not currently in the notification set of the process. The signal specified by signo is removed from pending for the process and is made pending for the target_lwp . If there is an associated siginfo information structure queued at the process, that siginfo is queued to the target_lwp .

Whenever a signal is cleared from the set of signals pending for the process, the corresponding signal is cleared from the notification set. After a successful call to _lwp_sigredirect() , the signal signo is cleared from the notification set and from the set of signals pending for the process. If another instance of signo is queued for the process, the signal number is again set in the process pending mask, and if another LWP is blocked in a call to _signotifywait() , its wait for an unnotified signal will be satisfied. The effects described in this paragraph also apply when the signal signo is returned by a call to sigtimedwait() and signo was not pending for the calling LWP.

When queued is non-NULL, and there is another instance of the signal (signo ), a non-zero value will be place in queued to indicate that more than one instance of the signal is pending on the process.

RETURN VALUES

The _signotifywait() function returns the signal number of the pending but hitherto unnotified signal. The _lwp_sigredirect() function returns 0 when successful. A non-zero value indicates an error.

ERRORS

No error conditions are specified for _signotifywait() .

If the following conditions occurs, _lwp_sigredirect() fails and return the corresponding value:

EINVAL

The signal signo was not pending for the process, or signo was not in the notification set.

ESRCH

The target_lwp cannot be found in the current process.

SEE ALSO

_lwp_create(2) , _lwp_kill(2) , sigtimedwait(3RT) , siginfo(3HEAD) , signal(3HEAD)

NOTES

This mechanism for delivering signals to multithreaded processes is subject to change in future versions of Solaris. Any process with explicit knowledge of this mechanism may not be compatible from release to release.

SunOS 5.8  Last Revised 21 Oct 1998

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | NOTES