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, 8 insertions, 32 deletions

diff --git a/lib/libc_r/uthread/uthread_setprio.c b/lib/libc_r/uthread/uthread_setprio.c
index 4b49ed0..dd89f15 100644
--- a/lib/libc_r/uthread/uthread_setprio.c
+++ b/lib/libc_r/uthread/uthread_setprio.c
@@ -38,43 +38,19 @@
 int
 pthread_setprio(pthread_t pthread, int prio)
 {
-	int             rval = 0;
-	int             status;
-	pthread_t       pthread_p;
+	int ret;
 
 	/* Check if the priority is invalid: */
-	if (prio < PTHREAD_MIN_PRIORITY || prio > PTHREAD_MAX_PRIORITY) {
+	if (prio < PTHREAD_MIN_PRIORITY || prio > PTHREAD_MAX_PRIORITY)
 		/* Return an invalid argument error: */
-		errno = EINVAL;
-		rval = -1;
-	} else {
-		/* Block signals: */
-		_thread_kern_sig_block(&status);
+		ret = EINVAL;
 
-		/* Point to the first thread in the list: */
-		pthread_p = _thread_link_list;
-
-		/* Enter a loop to search for the thread: */
-		while (pthread_p != NULL && pthread_p != pthread) {
-			/* Point to the next thread: */
-			pthread_p = pthread_p->nxt;
-		}
-
-		/* Check if the thread pointer is NULL: */
-		if (pthread == NULL || pthread_p == NULL) {
-			/* Return a 'search' error: */
-			errno  = ESRCH;
-			rval = -1;
-		} else {
-			/* Set the thread priority: */
-			pthread->pthread_priority = prio;
-		}
-
-		/* Unblock signals: */
-		_thread_kern_sig_unblock(status);
-	}
+	/* Find the thread in the list of active threads: */
+	else if ((ret = _find_thread(pthread)) == 0)
+		/* Set the thread priority: */
+		pthread->pthread_priority = prio;
 
 	/* Return the error status: */
-	return (rval);
+	return (ret);
 }
 #endif