Am 27.03.2012 um 22:22 schrieb Tilghman Lesher:

On Tue, Mar 27, 2012 at 1:57 PM, Nat! <nat@mulle-kybernetik.com> wrote:

...

instead of many words, here's the output of two program runs once with a sleep( 2) - as in seconds, not as in man - commented in and out. What I believe this demonstrates, is that on Darwin (Kernel Version 10.8.0), blocked signal information is lost, which is incovenient. gdb has a similiar problem.

Or it shows that I am misunderstanding something ;)

The problem is not that the signal is occurring less often, that's expected, but that the struct __siginfo has trouble remembering things.

You really should read the manpage for sigaction, in particular, the section that reads:

"In general though, signal handlers should do little more than set a flag; most other actions are not safe."

Note, also, that printf() is not in the list of "safe" functions to call. Thus your call to p_log is defined as not safe. While sleep() is safe to call, it also violates one of the cardinal rules of signal handlers -- do only what is necessary to flag that a signal occurred, and do not take more time than is necessary. The actual handling of what the signal represents should be done in a main thread.

-Tilghman

Tilghman, do you really think printf will magically erase struct __siginfo.si_pid ahead of printf even being called ? To make you feel better, appended is the same code, without printf, "surprisingly" with the same result. Ciao Nat! #include <errno.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> static void p_log( char *s) { printf( "%d: %s\n", getpid(), s); } static struct __siginfo memo; static void signal_action( int signal, struct __siginfo *info, void *data) { memo = *info; /// COMMENT-UNCOMMENT /// sleep( 2); } static void _test( void) { p_log( "fork"); if( ! fork()) { p_log( "kill"); kill( getppid(), SIGUSR1); p_log( "sleep"); sleep( 1); p_log( "kill"); kill( getppid(), SIGUSR1); p_log( "sleep"); sleep( 1); p_log( "_exit"); _exit( 0); } } int main( int argc, char *argv[]) { struct sigaction act; int status; sigemptyset( &act.sa_mask); act.__sigaction_u.__sa_sigaction = signal_action; act.sa_flags = SA_SIGINFO|SA_RESTART; p_log( "sigaction"); sigaction( SIGUSR1, &act, NULL); _test(); _test(); p_log( "wait"); while( wait( &status) == -1); p_log( "wait"); while( wait( &status) == -1); printf( "%d: memo = { %d, %d, %d, %d }\n", getpid(), memo.si_signo, memo.si_errno, memo.si_code, memo.si_pid); p_log( "_exit"); _exit( 0); } --------------------------------------------------- I learned that a cynic is the name given to people, who know what’s coming by people who don’t, and have regarded it as a compliment ever since. -- J. Watkinson _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app... This email sent to site_archiver@lists.apple.com