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, 4 insertions, 8 deletions

diff --git a/lib/libpthread/thread/thr_sigprocmask.c b/lib/libpthread/thread/thr_sigprocmask.c
index b4a8d84940eb..81b602f581c8 100644
--- a/lib/libpthread/thread/thr_sigprocmask.c
+++ b/lib/libpthread/thread/thr_sigprocmask.c
@@ -39,8 +39,7 @@
 int
 sigprocmask(int how, const sigset_t * set, sigset_t * oset)
 {
-	int             ret = 0;
-	int             status;
+	int ret = 0;
 
 	/* Check if the existing signal process mask is to be returned: */
 	if (oset != NULL) {
@@ -49,9 +48,6 @@ sigprocmask(int how, const sigset_t * set, sigset_t * oset)
 	}
 	/* Check if a new signal set was provided by the caller: */
 	if (set != NULL) {
-		/* Block signals while the signal mask is changed: */
-		_thread_kern_sig_block(&status);
-
 		/* Process according to what to do: */
 		switch (how) {
 		/* Block signals: */
@@ -81,10 +77,10 @@ sigprocmask(int how, const sigset_t * set, sigset_t * oset)
 		}
 
 		/*
-		 * Schedule the next thread in case there are signals that
-		 * now need to be acted on: 
+		 * Dispatch signals to the running thread that are pending
+		 * and now unblocked:
 		 */
-		_thread_kern_sched(NULL);
+		_dispatch_signals();
 	}
 	/* Return the completion status: */
 	return (ret);