Change signal model to match POSIX (i.e. one set of signal handlers

for the process, not a separate set for each thread). By default, the
process now only has signal handlers installed for SIGVTALRM, SIGINFO
and SIGCHLD. The thread kernel signal handler is installed for other
signals on demand. This means that SIG_IGN and SIG_DFL processing is now
left to the kernel, not the thread kernel.

Change the signal dispatch to no longer use a signal thread, and
call the signal handler using the stack of the thread that has the
signal pending.

Change the atomic lock method to use test-and-set asm code with
a yield if blocked. This introduces separate locks for each type
of object instead of blocking signals to prevent a context
switch. It was this blocking of signals that caused the performance
degradation the people have noted.

This is a *big* change!

1 files changed, 37 insertions, 15 deletions

diff --git a/lib/libkse/thread/thr_sigaction.c b/lib/libkse/thread/thr_sigaction.c
index dd08405..3538f27 100644
--- a/lib/libkse/thread/thr_sigaction.c
+++ b/lib/libkse/thread/thr_sigaction.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
+ * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -39,8 +39,8 @@
 int
 sigaction(int sig, const struct sigaction * act, struct sigaction * oact)
 {
-	int             ret = 0;
-	int             status;
+	int ret = 0;
+	struct sigaction gact;
 
 	/* Check if the signal number is out of range: */
 	if (sig < 1 || sig > NSIG) {
@@ -54,25 +54,47 @@ sigaction(int sig, const struct sigaction * act, struct sigaction * oact)
 		 */
 		if (oact != NULL) {
 			/* Return the existing signal action contents: */
-			oact->sa_handler = _thread_run->act[sig - 1].sa_handler;
-			oact->sa_mask = _thread_run->act[sig - 1].sa_mask;
-			oact->sa_flags = _thread_run->act[sig - 1].sa_flags;
+			oact->sa_handler = _thread_sigact[sig - 1].sa_handler;
+			oact->sa_mask = _thread_sigact[sig - 1].sa_mask;
+			oact->sa_flags = _thread_sigact[sig - 1].sa_flags;
 		}
+
 		/* Check if a signal action was supplied: */
 		if (act != NULL) {
-			/* Block signals while the signal handler is changed: */
-			_thread_kern_sig_block(&status);
-
 			/* Set the new signal handler: */
-			_thread_run->act[sig - 1].sa_handler = act->sa_handler;
-			_thread_run->act[sig - 1].sa_mask = act->sa_mask;
-			_thread_run->act[sig - 1].sa_flags = act->sa_flags;
+			_thread_sigact[sig - 1].sa_mask = act->sa_mask;
+			_thread_sigact[sig - 1].sa_flags = act->sa_flags;
+			_thread_sigact[sig - 1].sa_handler = act->sa_handler;
+		}
+
+		/*
+		 * Check if the kernel needs to be advised of a change
+		 * in signal action:
+		 */
+		if (act != NULL && sig != SIGVTALRM && sig != SIGCHLD &&
+		    sig != SIGINFO) {
+			/* Initialise the global signal action structure: */
+			gact.sa_mask = act->sa_mask;
+			gact.sa_flags = act->sa_flags | SA_RESTART;
 
 			/*
-			 * Unblock signals to allow the new signal handler to
-			 * take effect: 
+			 * Check if the signal handler is being set to
+			 * the default or ignore handlers:
 			 */
-			_thread_kern_sig_unblock(status);
+			if (act->sa_handler == SIG_DFL ||
+			    act->sa_handler == SIG_IGN)
+				/* Specify the built in handler: */
+				gact.sa_handler = act->sa_handler;
+			else
+				/*
+				 * Specify the thread kernel signal
+				 * handler:
+				 */
+				gact.sa_handler = (void (*) ()) _thread_sig_handler;
+
+			/* Change the signal action in the kernel: */
+		    	if (_thread_sys_sigaction(sig,&gact,NULL) != 0)
+				ret = -1;
 		}
 	}