Don't needlessly poll file descriptors when there are no

file descriptors needing to be polled (Doh!).  Reported
by Dan Nelson <dnelson@emsphone.com>.

Don't install and start the scheduling timer until the
first thread is created.  This prevents the overhead of
having a periodic scheduling signal in a single threaded
program.  Reported by Dan Nelson <dnelson@emsphone.com>.

Allow builtin longjmps out of application installed
signal handlers without the need perform any post-handler
cleanup:

  o Change signal handling to save the threads interrupted
    context on the stack.  The threads current context is
    now always stored in the same place (in the pthread).
    If and when a signal handler returns, the interrupted
    context is copied back to the storage area in the pthread.

  o Before calling invoking a signal handler for a thread,
    back the thread out of any internal waiting queues
    (mutex, CV, join, etc) to which it belongs.

Rework uthread_info.c a bit to make it easier to change
the format of a thread dump.

Use an alternal signal stack for the thread library's
signal handler.  This allows us to fiddle with the main
threads stack without fear of it being in use.

Reviewed by:	jasone

1 files changed, 25 insertions, 29 deletions

diff --git a/lib/libc_r/uthread/uthread_init.c b/lib/libc_r/uthread/uthread_init.c
index 3cbd453..35731c4 100644
--- a/lib/libc_r/uthread/uthread_init.c
+++ b/lib/libc_r/uthread/uthread_init.c
@@ -92,7 +92,7 @@ _thread_init(void)
 	int		mib[2];
 	struct clockinfo clockinfo;
 	struct sigaction act;
-	struct itimerval itimer;
+	struct sigaltstack alt;
 
 	/* Check if this function has already been called: */
 	if (_thread_initial)
@@ -133,7 +133,7 @@ _thread_init(void)
 
 	/*
 	 * Create a pipe that is written to by the signal handler to prevent
-	 * signals being missed in calls to _select: 
+	 * signals being missed in calls to _select:
 	 */
 	if (_thread_sys_pipe(_thread_kern_pipe) != 0) {
 		/* Cannot create pipe, so abort: */
@@ -168,12 +168,12 @@ _thread_init(void)
 	else if ((_thread_initial = (pthread_t) malloc(sizeof(struct pthread))) == NULL) {
 		/*
 		 * Insufficient memory to initialise this application, so
-		 * abort: 
+		 * abort:
 		 */
 		PANIC("Cannot allocate memory for initial thread");
 	}
 	/* Allocate memory for the scheduler stack: */
-	else if ((_thread_kern_sched_stack = malloc(PAGE_SIZE * 10)) == NULL)
+	else if ((_thread_kern_sched_stack = malloc(SCHED_STACK_SIZE)) == NULL)
 		PANIC("Failed to allocate stack for scheduler");
 	else {
 		/* Zero the global kernel thread structure: */
@@ -217,8 +217,8 @@ _thread_init(void)
 
 		/* Setup the context for the scheduler: */
 		_setjmp(_thread_kern_sched_jb);
-		SET_STACK_JB(_thread_kern_sched_jb,
-		    _thread_kern_sched_stack + PAGE_SIZE*10 - sizeof(double));
+		SET_STACK_JB(_thread_kern_sched_jb, _thread_kern_sched_stack +
+		    SCHED_STACK_SIZE - sizeof(double));
 		SET_RETURN_ADDR_JB(_thread_kern_sched_jb, _thread_kern_scheduler);
 
 		/*
@@ -253,12 +253,9 @@ _thread_init(void)
 		/* Initialize last active: */
 		_thread_initial->last_active = (long) _sched_ticks;
 
-		/* Initialize the initial signal frame: */
-		_thread_initial->sigframes[0] = &_thread_initial->sigframe0;
-		_thread_initial->curframe = &_thread_initial->sigframe0;
-		_thread_initial->curframe->ctxtype = CTX_JB_NOSIG;
-		/* Set the base of the stack: */
-		_thread_initial->curframe->stackp = (unsigned long) USRSTACK;
+		/* Initialize the initial context: */
+		_thread_initial->curframe = NULL;
+		_thread_initial->ctxtype = CTX_JB_NOSIG;
 
 		/* Initialise the rest of the fields: */
 		_thread_initial->poll_data.nfds = 0;
@@ -276,7 +273,7 @@ _thread_init(void)
 		/* Initialise the global signal action structure: */
 		sigfillset(&act.sa_mask);
 		act.sa_handler = (void (*) ()) _thread_sig_handler;
-		act.sa_flags = SA_SIGINFO;
+		act.sa_flags = SA_SIGINFO | SA_ONSTACK;
 
 		/* Clear pending signals for the process: */
 		sigemptyset(&_process_sigpending);
@@ -284,6 +281,13 @@ _thread_init(void)
 		/* Clear the signal queue: */
 		memset(_thread_sigq, 0, sizeof(_thread_sigq));
 
+		/* Create and install an alternate signal stack: */
+		alt.ss_sp = malloc(SIGSTKSZ);	/* recommended stack size */
+		alt.ss_size = SIGSTKSZ;
+		alt.ss_flags = 0;
+		if (_thread_sys_sigaltstack(&alt, NULL) != 0)
+			PANIC("Unable to install alternate signal stack");
+
 		/* Enter a loop to get the existing signal status: */
 		for (i = 1; i < NSIG; i++) {
 			/* Check for signals which cannot be trapped: */
@@ -295,7 +299,7 @@ _thread_init(void)
 			    &_thread_sigact[i - 1]) != 0) {
 				/*
 				 * Abort this process if signal
-				 * initialisation fails: 
+				 * initialisation fails:
 				 */
 				PANIC("Cannot read signal handler info");
 			}
@@ -313,7 +317,7 @@ _thread_init(void)
 		    _thread_sys_sigaction(SIGINFO,       &act, NULL) != 0 ||
 		    _thread_sys_sigaction(SIGCHLD,       &act, NULL) != 0) {
 			/*
-			 * Abort this process if signal initialisation fails: 
+			 * Abort this process if signal initialisation fails:
 			 */
 			PANIC("Cannot initialise signal handler");
 		}
@@ -335,7 +339,7 @@ _thread_init(void)
 		if ((_thread_dtablesize = getdtablesize()) < 0) {
 			/*
 			 * Cannot get the system defined table size, so abort
-			 * this process. 
+			 * this process.
 			 */
 			PANIC("Cannot get dtablesize");
 		}
@@ -346,7 +350,7 @@ _thread_init(void)
 
 			/*
 			 * Cannot allocate memory for the file descriptor
-			 * table, so abort this process. 
+			 * table, so abort this process.
 			 */
 			PANIC("Cannot allocate memory for file descriptor table");
 		}
@@ -354,13 +358,13 @@ _thread_init(void)
 		if ((_thread_pfd_table = (struct pollfd *) malloc(sizeof(struct pollfd) * _thread_dtablesize)) == NULL) {
 			/*
 			 * Cannot allocate memory for the file descriptor
-			 * table, so abort this process. 
+			 * table, so abort this process.
 			 */
 			PANIC("Cannot allocate memory for pollfd table");
 		} else {
 			/*
 			 * Enter a loop to initialise the file descriptor
-			 * table: 
+			 * table:
 			 */
 			for (i = 0; i < _thread_dtablesize; i++) {
 				/* Initialise the file descriptor table: */
@@ -374,14 +378,6 @@ _thread_init(void)
 					PANIC("Cannot initialize stdio file "
 					    "descriptor table entry");
 			}
-
-			/* Install the scheduling timer: */
-			itimer.it_interval.tv_sec = 0;
-			itimer.it_interval.tv_usec = _clock_res_usec;
-			itimer.it_value = itimer.it_interval;
-			if (setitimer(_ITIMER_SCHED_TIMER, &itimer, NULL) != 0)
-				PANIC("Cannot set interval timer");
-
 		}
 	}
 
@@ -401,10 +397,10 @@ _thread_init(void)
 }
 
 /*
- * Special start up code for NetBSD/Alpha 
+ * Special start up code for NetBSD/Alpha
  */
 #if	defined(__NetBSD__) && defined(__alpha__)
-int 
+int
 main(int argc, char *argv[], char *env);
 
 int