[ale] SIGHUP ignored after exec

[Joe Steele]

Two issues are at play:

1) When a signal handler is invoked, the signal which it catches is 
blocked until the handler returns or until the signal is explicitly 
unblocked.  

2)  When you exec() a new program, the new program inherits the 
signal mask of the previous program.

In your case, when the SIGHUP arrives, the signal mask is changed to 
block the signal and the signal handler is called.  The signal 
handler never returns, but instead calls exec(), so the new program 
inherits the signal mask which has SIGHUP blocked.

You need to change your main program so that after it calls signal(), 
it unblocks SIGHUP, roughly like this:

sigset_t myset;
...
sigemptyset (&myset);
sigaddset (&myset, SIGHUP);
signal (SIGHUP, sigCatcher);
sigprocmask (SIG_UNBLOCK, &myset, NULL);

--Joe


-----Original Message-----
From:	Chris Fowler [SMTP:cfowler at outpostsentinel.com]
Sent:	Monday, March 25, 2002 2:38 PM
To:	ale at ale.org
Subject:	[ale] SIGHUP ignored after exec

Hello,

I have an issue where I use SIGHUP to reintialize a program.  The way I do this is just have the program exec itself.  The exec works but it appears that
all attempts to send SIGHUP to the new program fail.  It is ignoring those signals.  Below is strace output and I also have attached test  
code.  I may be using my syscalls incorreclty.  Having a program reexec itself is easier than re-reading configuration.


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