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, 33 insertions, 124 deletions

diff --git a/lib/libc_r/uthread/uthread_jmp.c b/lib/libc_r/uthread/uthread_jmp.c
index f2c38c2..db19ebd 100644
--- a/lib/libc_r/uthread/uthread_jmp.c
+++ b/lib/libc_r/uthread/uthread_jmp.c
@@ -40,163 +40,72 @@
 #include <pthread.h>
 #include "pthread_private.h"
 
+/* Prototypes: */
+static inline int	check_stack(pthread_t thread, void *stackp);
+
 void
 siglongjmp(sigjmp_buf env, int savemask)
 {
-	void	*jmp_stackp;
-	void	*stack_begin, *stack_end;
-	int	frame, dst_frame;
-
-	if ((frame = _thread_run->sigframe_count) == 0)
-		__siglongjmp(env, savemask);
-
-	/* Get the stack pointer from the jump buffer. */
-	jmp_stackp = (void *) GET_STACK_SJB(env);
-
-	/* Get the bounds of the current threads stack. */
-	PTHREAD_ASSERT(_thread_run->stack != NULL,
-	    "Thread stack pointer is null");
-	stack_begin = _thread_run->stack;
-	stack_end = stack_begin + _thread_run->attr.stacksize_attr;
-
-	/*
-	 * Make sure we aren't jumping to a different stack.  Make sure
-	 * jmp_stackp is between stack_begin and stack end, to correctly detect
-	 * this condition regardless of whether the stack grows up or down.
-	 */
-	if (((jmp_stackp < stack_begin) && (jmp_stackp < stack_end)) ||
-	    ((jmp_stackp > stack_begin) && (jmp_stackp > stack_end)))
+	if (check_stack(_thread_run, (void *) GET_STACK_SJB(env)))
 		PANIC("siglongjmp()ing between thread contexts is undefined by "
 		    "POSIX 1003.1");
 
-	if ((dst_frame = _thread_sigframe_find(_thread_run, jmp_stackp)) < 0)
-		/*
-		 * The stack pointer was verified above, so this
-		 * shouldn't happen.  Let's be anal anyways.
-		 */
-		PANIC("Error locating signal frame");
-	else if (dst_frame == frame) {
-		/*
-		 * The stack pointer is somewhere within the current
-		 * frame.  Jump to the users context.
-		 */
-		__siglongjmp(env, savemask);
-	}
 	/*
-	 * Copy the users context to the return context of the
-	 * destination frame.
+	 * The stack pointer is somewhere within the threads stack.
+	 * Jump to the users context.
 	 */
-	memcpy(&_thread_run->sigframes[dst_frame]->ctx.sigjb, env, sizeof(*env));
-	_thread_run->sigframes[dst_frame]->ctxtype = CTX_SJB;
-	_thread_run->sigframes[dst_frame]->longjmp_val = savemask;
-	_thread_run->curframe->dst_frame = dst_frame;
-	___longjmp(*_thread_run->curframe->sig_jb, 1);
+	__siglongjmp(env, savemask);
 }
 
 void
 longjmp(jmp_buf env, int val)
 {
-	void	*jmp_stackp;
-	void	*stack_begin, *stack_end;
-	int	frame, dst_frame;
-
-	if ((frame = _thread_run->sigframe_count) == 0)
-		__longjmp(env, val);
-
-	/* Get the stack pointer from the jump buffer. */
-	jmp_stackp = (void *) GET_STACK_JB(env);
-
-	/* Get the bounds of the current threads stack. */
-	PTHREAD_ASSERT(_thread_run->stack != NULL,
-	    "Thread stack pointer is null");
-	stack_begin = _thread_run->stack;
-	stack_end = stack_begin + _thread_run->attr.stacksize_attr;
-
-	/*
-	 * Make sure we aren't jumping to a different stack.  Make sure
-	 * jmp_stackp is between stack_begin and stack end, to correctly detect
-	 * this condition regardless of whether the stack grows up or down.
-	 */
-	if (((jmp_stackp < stack_begin) && (jmp_stackp < stack_end)) ||
-	    ((jmp_stackp > stack_begin) && (jmp_stackp > stack_end)))
+	if (check_stack(_thread_run, (void *) GET_STACK_JB(env)))
 		PANIC("longjmp()ing between thread contexts is undefined by "
 		    "POSIX 1003.1");
 
-	if ((dst_frame = _thread_sigframe_find(_thread_run, jmp_stackp)) < 0)
-		/*
-		 * The stack pointer was verified above, so this
-		 * shouldn't happen.  Let's be anal anyways.
-		 */
-		PANIC("Error locating signal frame");
-	else if (dst_frame == frame) {
-		/*
-		 * The stack pointer is somewhere within the current
-		 * frame.  Jump to the users context.
-		 */
-		__longjmp(env, val);
-	}
-
 	/*
-	 * Copy the users context to the return context of the
-	 * destination frame.
+	 * The stack pointer is somewhere within the threads stack.
+	 * Jump to the users context.
 	 */
-	memcpy(&_thread_run->sigframes[dst_frame]->ctx.jb, env, sizeof(*env));
-	_thread_run->sigframes[dst_frame]->ctxtype = CTX_JB;
-	_thread_run->sigframes[dst_frame]->longjmp_val = val;
-	_thread_run->curframe->dst_frame = dst_frame;
-	___longjmp(*_thread_run->curframe->sig_jb, 1);
+	__longjmp(env, val);
 }
 
 void
 _longjmp(jmp_buf env, int val)
 {
-	void	*jmp_stackp;
-	void	*stack_begin, *stack_end;
-	int	frame, dst_frame;
+	if (check_stack(_thread_run, (void *) GET_STACK_JB(env)))
+		PANIC("_longjmp()ing between thread contexts is undefined by "
+		    "POSIX 1003.1");
 
-	if ((frame = _thread_run->sigframe_count) == 0)
-		___longjmp(env, val);
+	/*
+	 * The stack pointer is somewhere within the threads stack.
+	 * Jump to the users context.
+	 */
+	___longjmp(env, val);
+}
 
-	/* Get the stack pointer from the jump buffer. */
-	jmp_stackp = (void *) GET_STACK_JB(env);
+/* Returns 0 if stack check is OK, non-zero otherwise. */
+static inline int
+check_stack(pthread_t thread, void *stackp)
+{
+	void	*stack_begin, *stack_end;
 
 	/* Get the bounds of the current threads stack. */
-	PTHREAD_ASSERT(_thread_run->stack != NULL,
+	PTHREAD_ASSERT(thread->stack != NULL,
 	    "Thread stack pointer is null");
-	stack_begin = _thread_run->stack;
-	stack_end = stack_begin + _thread_run->attr.stacksize_attr;
+	stack_begin = thread->stack;
+	stack_end = stack_begin + thread->attr.stacksize_attr;
 
 	/*
 	 * Make sure we aren't jumping to a different stack.  Make sure
 	 * jmp_stackp is between stack_begin and stack end, to correctly detect
 	 * this condition regardless of whether the stack grows up or down.
 	 */
-	if (((jmp_stackp < stack_begin) && (jmp_stackp < stack_end)) ||
-	    ((jmp_stackp > stack_begin) && (jmp_stackp > stack_end)))
-		PANIC("_longjmp()ing between thread contexts is undefined by "
-		    "POSIX 1003.1");
-
-	if ((dst_frame = _thread_sigframe_find(_thread_run, jmp_stackp)) < 0)
-		/*
-		 * The stack pointer was verified above, so this
-		 * shouldn't happen.  Let's be anal anyways.
-		 */
-		PANIC("Error locating signal frame");
-	else if (dst_frame == frame) {
-		/*
-		 * The stack pointer is somewhere within the current
-		 * frame.  Jump to the users context.
-		 */
-		___longjmp(env, val);
-	}
-	/*
-	 * Copy the users context to the return context of the
-	 * destination frame.
-	 */
-	memcpy(&_thread_run->sigframes[dst_frame]->ctx.jb, env, sizeof(*env));
-	_thread_run->sigframes[dst_frame]->ctxtype = CTX_JB_NOSIG;
-	_thread_run->sigframes[dst_frame]->longjmp_val = val;
-	_thread_run->curframe->dst_frame = dst_frame;
-	___longjmp(*_thread_run->curframe->sig_jb, 1);
+	if (((stackp < stack_begin) && (stackp < stack_end)) ||
+	    ((stackp > stack_begin) && (stackp > stack_end)))
+		return (1);
+	else
+		return (0);
 }
 #endif