add pthread_cancel, obtained from OpenBSD.

eischen (Daniel Eischen) added wrappers to protect against cancled
threads orphaning internal resources.

the cancelability code is still a bit fuzzy but works for test
programs of my own, OpenBSD's and some examples from ORA's books.

add readdir_r to both libc and libc_r

add some 'const' attributes to function parameters

Reviewed by: eischen, jasone

1 files changed, 179 insertions, 0 deletions

diff --git a/lib/libpthread/thread/thr_cancel.c b/lib/libpthread/thread/thr_cancel.c
new file mode 100644
index 0000000..bad5533
--- /dev/null
+++ b/lib/libpthread/thread/thr_cancel.c
@@ -0,0 +1,179 @@
+/*
+ * David Leonard <d@openbsd.org>, 1999. Public domain.
+ * $FreeBSD$
+ */
+
+#include <sys/errno.h>
+#include <pthread.h>
+#include "pthread_private.h"
+
+int
+pthread_cancel(pthread_t pthread)
+{
+	int ret;
+
+	if ((ret = _find_thread(pthread)) != 0) {
+		/* NOTHING */
+	} else if (pthread->state == PS_DEAD || pthread->state == PS_DEADLOCK) {
+		ret = 0;
+	} else {
+		/* Protect the scheduling queues: */
+		_thread_kern_sig_defer();
+
+		/* Check if we need to kick it back into the run queue: */
+		if ((pthread->cancelflags & PTHREAD_CANCEL_DISABLE) == 0)
+			switch (pthread->state) {
+			case PS_RUNNING:
+				/* No need to resume: */
+				pthread->cancelflags |= PTHREAD_CANCELLING;
+				break;
+
+			case PS_SPINBLOCK:
+			case PS_FDR_WAIT:
+			case PS_FDW_WAIT:
+			case PS_POLL_WAIT:
+			case PS_SELECT_WAIT:
+			/* Remove these threads from the work queue: */
+				if ((pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
+				    != 0)
+					PTHREAD_WORKQ_REMOVE(pthread);
+				/* Fall through: */
+			case PS_SIGTHREAD:
+			case PS_SLEEP_WAIT:
+			case PS_WAIT_WAIT:
+			case PS_SIGSUSPEND:
+			case PS_SIGWAIT:
+			case PS_SUSPENDED:
+				/* Interrupt and resume: */
+				pthread->interrupted = 1;
+				pthread->cancelflags |= PTHREAD_CANCELLING;
+				PTHREAD_NEW_STATE(pthread,PS_RUNNING);
+				break;
+
+			case PS_MUTEX_WAIT:
+			case PS_COND_WAIT:
+			case PS_FDLR_WAIT:
+			case PS_FDLW_WAIT:
+			case PS_FILE_WAIT:
+			case PS_JOIN:
+				/*
+				 * Threads in these states may be in queues.
+				 * In order to preserve queue integrity, the
+				 * cancelled thread must remove itself from the
+				 * queue.  Mark the thread as interrupted and
+				 * needing cancellation, and set the state to
+				 * running.  When the thread resumes, it will
+				 * exit after removing itself from the queue.
+				 */
+				pthread->interrupted = 1;
+				pthread->cancelflags |= PTHREAD_CANCEL_NEEDED;
+				PTHREAD_NEW_STATE(pthread,PS_RUNNING);
+				break;
+
+			case PS_DEAD:
+			case PS_DEADLOCK:
+			case PS_STATE_MAX:
+				/* Ignore - only here to silence -Wall: */
+				break;
+		}
+		/* Unprotect the scheduling queues: */
+		_thread_kern_sig_undefer();
+
+		ret = 0;
+	}
+	return (ret);
+}
+
+int
+pthread_setcancelstate(int state, int *oldstate)
+{
+	int ostate;
+	int ret;
+
+	ostate = _thread_run->cancelflags & PTHREAD_CANCEL_DISABLE;
+
+	switch (state) {
+	case PTHREAD_CANCEL_ENABLE:
+		if (oldstate != NULL)
+			*oldstate = ostate;
+		_thread_run->cancelflags &= PTHREAD_CANCEL_ENABLE;
+		if ((_thread_run->cancelflags & PTHREAD_CANCEL_ASYNCHRONOUS) != 0)
+			pthread_testcancel();
+		ret = 0;
+		break;
+	case PTHREAD_CANCEL_DISABLE:
+		if (oldstate != NULL)
+			*oldstate = ostate;
+		_thread_run->cancelflags |= PTHREAD_CANCEL_DISABLE;
+		ret = 0;
+		break;
+	default:
+		ret = EINVAL;
+	}
+
+	return (ret);
+}
+
+int
+pthread_setcanceltype(int type, int *oldtype)
+{
+	int otype;
+	int ret;
+
+	otype = _thread_run->cancelflags & PTHREAD_CANCEL_ASYNCHRONOUS;
+	switch (type) {
+	case PTHREAD_CANCEL_ASYNCHRONOUS:
+		if (oldtype != NULL)
+			*oldtype = otype;
+		_thread_run->cancelflags |= PTHREAD_CANCEL_ASYNCHRONOUS;
+		pthread_testcancel();
+		ret = 0;
+		break;
+	case PTHREAD_CANCEL_DEFERRED:
+		if (oldtype != NULL)
+			*oldtype = otype;
+		_thread_run->cancelflags &= ~PTHREAD_CANCEL_ASYNCHRONOUS;
+		ret = 0;
+		break;
+	default:
+		ret = EINVAL;
+	}
+
+	return (ret);
+}
+
+void
+pthread_testcancel(void)
+{
+
+	if (((_thread_run->cancelflags & PTHREAD_CANCEL_DISABLE) == 0) &&
+	    ((_thread_run->cancelflags & PTHREAD_CANCELLING) != 0)) {
+		/*
+		 * It is possible for this thread to be swapped out
+		 * while performing cancellation; do not allow it
+		 * to be cancelled again.
+		 */
+		_thread_run->cancelflags &= ~PTHREAD_CANCELLING;
+		_thread_exit_cleanup();
+		pthread_exit(PTHREAD_CANCELED);
+		PANIC("cancel");
+	}
+}
+
+void
+_thread_enter_cancellation_point(void)
+{
+
+	/* Look for a cancellation before we block: */
+	pthread_testcancel();
+	_thread_run->cancelflags |= PTHREAD_AT_CANCEL_POINT;
+}
+
+void
+_thread_leave_cancellation_point(void)
+{
+
+	_thread_run->cancelflags &= ~PTHREAD_AT_CANCEL_POINT;
+	/* Look for a cancellation after we unblock: */
+	pthread_testcancel();
+}