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, 27 insertions, 122 deletions

diff --git a/lib/libpthread/thread/thr_create.c b/lib/libpthread/thread/thr_create.c
index c9c6c9f..7603dd3 100644
--- a/lib/libpthread/thread/thr_create.c
+++ b/lib/libpthread/thread/thr_create.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
@@ -43,8 +43,8 @@
 #include "libc_private.h"
 
 int
-_thread_create(pthread_t * thread, const pthread_attr_t * attr,
-	       void *(*start_routine) (void *), void *arg, pthread_t parent)
+pthread_create(pthread_t * thread, const pthread_attr_t * attr,
+	       void *(*start_routine) (void *), void *arg)
 {
 	int             i;
 	int             ret = 0;
@@ -53,8 +53,11 @@ _thread_create(pthread_t * thread, const pthread_attr_t * attr,
 	pthread_attr_t	pattr;
 	void           *stack;
 
-	/* Block signals: */
-	_thread_kern_sig_block(&status);
+	/*
+	 * Locking functions in libc are required when there are
+	 * threads other than the initial thread.
+	 */
+	__isthreaded = 1;
 
 	/* Allocate memory for the thread structure: */
 	if ((new_thread = (pthread_t) malloc(sizeof(struct pthread))) == NULL) {
@@ -103,71 +106,33 @@ _thread_create(pthread_t * thread, const pthread_attr_t * attr,
 			/* Initialise the thread for signals: */
 			new_thread->sigmask = _thread_run->sigmask;
 
-			/*
-			 * Enter a loop to initialise the signal handler
-			 * array: 
-			 */
-			for (i = 1; i < NSIG; i++) {
-				/* Default the signal handler: */
-				sigfillset(&new_thread->act[i - 1].sa_mask);
-				new_thread->act[i - 1].sa_handler = _thread_run->act[i - 1].sa_handler;
-				new_thread->act[i - 1].sa_flags = _thread_run->act[i - 1].sa_flags;
-			}
-
 			/* Initialise the jump buffer: */
-			_thread_sys_setjmp(new_thread->saved_jmp_buf);
+			setjmp(new_thread->saved_jmp_buf);
 
 			/*
 			 * Set up new stack frame so that it looks like it
 			 * returned from a longjmp() to the beginning of
-			 * _thread_start(). Check if this is a user thread: 
+			 * _thread_start().
 			 */
-			if (parent == NULL) {
-				/* Use the user start function: */
 #if	defined(__FreeBSD__)
 #if	defined(__alpha__)
-				new_thread->saved_jmp_buf[0]._jb[2] = (long) _thread_start;
-				new_thread->saved_jmp_buf[0]._jb[4 + R_RA] = 0;
-				new_thread->saved_jmp_buf[0]._jb[4 + R_T12] = (long) _thread_start;
+			new_thread->saved_jmp_buf[0]._jb[2] = (long) _thread_start;
+			new_thread->saved_jmp_buf[0]._jb[4 + R_RA] = 0;
+			new_thread->saved_jmp_buf[0]._jb[4 + R_T12] = (long) _thread_start;
 #else
-				new_thread->saved_jmp_buf[0]._jb[0] = (long) _thread_start;
+			new_thread->saved_jmp_buf[0]._jb[0] = (long) _thread_start;
 #endif
 #elif	defined(__NetBSD__)
 #if	defined(__alpha__)
-				new_thread->saved_jmp_buf[2] = (long) _thread_start;
-				new_thread->saved_jmp_buf[4 + R_RA] = 0;
-				new_thread->saved_jmp_buf[4 + R_T12] = (long) _thread_start;
+			new_thread->saved_jmp_buf[2] = (long) _thread_start;
+			new_thread->saved_jmp_buf[4 + R_RA] = 0;
+			new_thread->saved_jmp_buf[4 + R_T12] = (long) _thread_start;
 #else
-				new_thread->saved_jmp_buf[0] = (long) _thread_start;
+			new_thread->saved_jmp_buf[0] = (long) _thread_start;
 #endif
 #else
 #error	"Don't recognize this operating system!"
 #endif
-			} else {
-				/*
-				 * Use the (funny) signal handler start
-				 * function: 
-				 */
-#if	defined(__FreeBSD__)
-#if	defined(__alpha__)
-				new_thread->saved_jmp_buf[0]._jb[2] = (long) _thread_start_sig_handler;
-				new_thread->saved_jmp_buf[0]._jb[4 + R_RA] = 0;
-				new_thread->saved_jmp_buf[0]._jb[4 + R_T12] = (long) _thread_start_sig_handler;
-#else
-				new_thread->saved_jmp_buf[0]._jb[0] = (int) _thread_start_sig_handler;
-#endif
-#elif	defined(__NetBSD__)
-#if	defined(__alpha__)
-				new_thread->saved_jmp_buf[2] = (long) _thread_start_sig_handler;
-				new_thread->saved_jmp_buf[4 + R_RA] = 0;
-				new_thread->saved_jmp_buf[4 + R_T12] = (long) _thread_start_sig_handler;
-#else
-				new_thread->saved_jmp_buf[0] = (long) _thread_start_sig_handler;
-#endif
-#else
-#error	"Don't recognize this operating system!"
-#endif
-			}
 
 			/* The stack starts high and builds down: */
 #if	defined(__FreeBSD__)
@@ -215,57 +180,26 @@ _thread_create(pthread_t * thread, const pthread_attr_t * attr,
 			new_thread->cleanup = NULL;
 			new_thread->queue = NULL;
 			new_thread->qnxt = NULL;
-			new_thread->parent_thread = parent;
 			new_thread->flags = 0;
 
+			/* Lock the thread list: */
+			_lock_thread_list();
+
 			/* Add the thread to the linked list of all threads: */
 			new_thread->nxt = _thread_link_list;
 			_thread_link_list = new_thread;
 
+			/* Unlock the thread list: */
+			_unlock_thread_list();
+
 			/* Return a pointer to the thread structure: */
-			if(thread)
-				(*thread) = new_thread;
+			(*thread) = new_thread;
 
-			/* Check if a parent thread was specified: */
-			if (parent != NULL) {
-				/*
-				 * A parent thread was specified, so this is
-				 * a signal handler thread which must now
-				 * wait for the signal handler to complete: 
-				 */
-				PTHREAD_NEW_STATE(parent,PS_SIGTHREAD);
-			} else {
-				/* Schedule the new user thread: */
-				_thread_kern_sched(NULL);
-			}
+			/* Schedule the new user thread: */
+			_thread_kern_sched(NULL);
 		}
 	}
 
-	/* Unblock signals: */
-	_thread_kern_sig_unblock(status);
-
-	/* Return the status: */
-	return (ret);
-}
-
-int
-pthread_create(pthread_t * thread, const pthread_attr_t * attr,
-	       void *(*start_routine) (void *), void *arg)
-{
-	int             ret = 0;
-
-	/*
-	 * Locking functions in libc are required when there are
-	 * threads other than the initial thread.
-	 */
-	__isthreaded = 1;
-
-	/*
-	 * Call the low level thread creation function which allows a parent
-	 * thread to be specified: 
-	 */
-	ret = _thread_create(thread, attr, start_routine, arg, NULL);
-
 	/* Return the status: */
 	return (ret);
 }
@@ -279,33 +213,4 @@ _thread_start(void)
 	/* This point should never be reached. */
 	PANIC("Thread has resumed after exit");
 }
-
-void
-_thread_start_sig_handler(void)
-{
-	int             sig;
-	long            arg;
-	void            (*sig_routine) (int);
-
-	/*
-	 * Cast the argument from 'void *' to a variable that is NO SMALLER
-	 * than a pointer (otherwise gcc under NetBSD/Alpha will complain): 
-	 */
-	arg = (long) _thread_run->arg;
-
-	/* Cast the argument as a signal number: */
-	sig = (int) arg;
-
-	/* Cast a pointer to the signal handler function: */
-	sig_routine = (void (*) (int)) _thread_run->start_routine;
-
-	/* Call the signal handler function: */
-	(*sig_routine) (sig);
-
-	/* Exit the signal handler thread: */
-	pthread_exit(&arg);
-
-	/* This point should never be reached. */
-	PANIC("Signal handler thread has resumed after exit");
-}
 #endif