signal handler problems Post: 302133815

Sponsored Content

Top Forums Programming signal handler problems Post 302133815 by matrixmadhan on Sunday 26th of August 2007 08:14:50 AM

08-26-2007

Registered User

Adding to Perderabo's comment on using newer semantics of signal handling instead of older semantics.

Using signal function, while executing the code block within the signal handler there is no guarantee that another signal of the same type delivered would be handled the same way; instead the second signal of the same type delivered would default to its default action which in most of the cases would be to terminate.

for example:

Code:

signal code block {
/*  code instruction is currently here */  <== this instruction point
}

when its at the " this instruction point " and if a signal is again delivered at this point, proper house keeping operations intended for the signal handler will not be completed.

But this never happens with the newer semantics with sigaction,
when the code instructions are executed within the signal action block kernel guarantees that it will not deliver the same signal type until the signal action block is completed.

so with the newer semantics you are guaranteed that your house keeping operations are done.

matrixmadhan

View Public Profile for matrixmadhan

Find all posts by matrixmadhan

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

shell script signal handler

AIX 4.3.3 I am trying to write a signal handler into a ksh shell script. I would like to capture the SIGTERM, SIGINT, and the SIGTSTP signals, print out a message to the terminal, and continue executing the script. I have found a way to block the signals: #! /bin/ksh SIGTERM=15 SIGINT=2...

2. Programming

signal handler for SIGCHLD

Hi, I have an c++ application which uses the function fork and execvp(). The parent does not wait until the child ends. The parents just creates children and let them do their stuff. You can see the parent program as a batch-manager. I have added a SIGCHLD handler to the program: void...

3. Programming

Runaway SIGALRM signal handler

I have written a program to demonstrate a problem I have encountered when using BSD style asynchronous input using the O_ASYNC flag in conjunction with a real time interval timer sending regular SIGALRM signals to the program. The SIGIO handler obeys all safe practices, using only an atomic update...

4. Programming

Usage of exit() inside a signal handler

Is it ok to use exit() inside a signal handler? I catch SIGUSR1 in a signal handler and I try to close a file and then exit. The result is inconsistent. Sometimes the process exit and sometimes it returns to the original state before the signal handler was invoked. Perhaps exit is not legal in...

5. Programming

Problem with signal handler and interrupted system call

Hi, I have a daq program that runs in an infinite loop until it receives SIGINT. A handler catches the signal and sets a flag to stop the while loop. After the loop some things have to be cleaned up. The problem is that I want my main while loop to wait until the next full second begins, to...

6. Shell Programming and Scripting

Perl - Problems with Signal Handler

I have a problem with signal handlers not working. I have a long 1000 line code and somehow this code for signal handling is not working: $SIG{INT} = \&interrupt; sub interrupt { print STDERR "Caught a control c!\n"; exit; # or just about anything else you'd want to do } Any...

7. Programming

Signal Handler Hangs

Hi, I have a problem with signal handler algorithm in linux. My code is hanging ( It is continuously looping inside the signal handler) . I am pasting my code here... Please provide me some help regarding this. I googled many places and wrote this code.. but doesnt seem to be working without...

8. Shell Programming and Scripting

Perl Signal Handler

I was working on some Perl code that does signal handling and I came across this one liner and wasn't sure what it was doing. local $SIG{__DIE__} = sub {$! = 2; die $_;}; I think the first part of the anonymous subroutine is setting $! to 2, but I am not sure what the second part is doing. ...

9. Programming

problem in doing coding of signal handler

i m unble to execute code of signal handler using a) Wait b) Waitpid

10. Programming

Serial port signal(IRQ) handler (using C)

Hello, I'm writing some serial(UART) handler but have stuck on few issues, maybe anyone can help to show me what I'm doing wrong. Basically I'm intending to write serial RX signal handler. Application receives defined packages of data over serial which contains header and payload. Handler...

LEARN ABOUT SUSE

sysv_signal

SYSV_SIGNAL(3)						     Linux Programmer's Manual						    SYSV_SIGNAL(3)

NAME

       sysv_signal - signal handling with System V semantics

SYNOPSIS

       #define _GNU_SOURCE
       #include <signal.h>

       typedef void (*sighandler_t)(int);

       sighandler_t sysv_signal(int signum, sighandler_t handler);

DESCRIPTION

       The sysv_signal() function takes the same arguments, and performs the same task, as signal(2).

       However	sysv_signal() provides the System V unreliable signal semantics, that is: a) the disposition of the signal is reset to the default
       when the handler is invoked; b) delivery of further instances of the signal is not blocked while the signal handler is executing; and c) if
       the handler interrupts (certain) blocking system calls, then the system call is not automatically restarted.

RETURN VALUE

       The sysv_signal() function returns the previous value of the signal handler, or SIG_ERR on error.

ERRORS

       As for signal(2).

CONFORMING TO

       This function is nonstandard.

NOTES

       Use of sysv_signal() should be avoided; use sigaction(2) instead.

       On  older  Linux systems, sysv_signal() and signal(2) were equivalent.  But on newer systems, signal(2) provides reliable signal semantics;
       see signal(2) for details.

       The use of sighandler_t is a GNU extension; this type is only defined if the _GNU_SOURCE feature test macro is defined.

SEE ALSO

       sigaction(2), signal(2), bsd_signal(3), feature_test_macros(7), signal(7)

COLOPHON

       This page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

								    2007-05-04							    SYSV_SIGNAL(3)

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

shell script signal handler

Discussion started by: jalburger

2. Programming

signal handler for SIGCHLD

Discussion started by: jens

3. Programming

Runaway SIGALRM signal handler

Discussion started by: stewartw

4. Programming

Usage of exit() inside a signal handler

Discussion started by: Tuvia