Add a regression test for the big pipe bug.

Suggested by: silby

tools/regression/README

@@ -22,6 +22,7 @@ geom		Some tests and an out-of-kernel simulator for the GEOM code
 ia64_unaligned	Tests unaligned reads on the IA64
 nfsmmap		Some tests to exercise some tricky cases in NFS and mmap
 p1003_1b	Exercise 1003.1B scheduler
+pipe		Pipe code regression test
 fsx		General filesystem exerciser
 sysvmsg 	SysV IPC Message Queue Regression Utility
 sysvsem 	SysV IPC Semaphore Regression Utility

tools/regression/pipe/Makefile

@@ -0,0 +1,16 @@
+#
+# $FreeBSD$
+#
+# "make" then "make regress".
+#
+PROG=	bigpipetest
+NOMAN=	yes
+
+regress:
+	@if ./bigpipetest; then \
+		echo "PASS"; \
+	else \
+		echo "FAIL"; \
+	fi
+
+.include <bsd.prog.mk>

tools/regression/pipe/bigpipetest.c

@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/select.h>
+#include <sys/pipe.h>
+#include <string.h>
+#include <errno.h>
+
+/*
+ * Test for the non-blocking big pipe bug (write(2) returning
+ * EAGAIN while select(2) returns the descriptor as ready for write).
+ *
+ * $FreeBSD$
+ */
+
+void write_frame(int fd, char *buf, unsigned long buflen)
+{
+    fd_set wfd;
+    int i;
+
+    while (buflen) {
+	FD_ZERO(&wfd);
+	FD_SET(fd, &wfd);
+	i = select(fd+1, NULL, &wfd, NULL, NULL);
+	if (i < 0) {
+	    perror("select");
+	    exit(1);
+	}
+	if (i != 1) {
+	    fprintf(stderr, "select returned unexpected value %d\n", i);
+	    exit(1);
+	}
+        i = write(fd, buf, buflen);
+	if (i < 0) {
+	    if (errno != EAGAIN)
+		perror("write");
+	    exit(1);
+	}
+        buf += i;
+        buflen -= i;
+    }
+}
+
+int main()
+{
+    char buf[BIG_PIPE_SIZE];	/* any value over PIPE_SIZE should do */
+    int i, flags, fd[2];
+
+    if (pipe(fd) < 0) { perror("pipe"); exit(1); }
+
+    flags = fcntl(fd[1], F_GETFL);
+    if (flags == -1 || fcntl(fd[1], F_SETFL, flags|O_NONBLOCK) == -1) {
+	perror("fcntl");
+	exit(1);
+    }
+
+    switch (fork()) {
+	case -1:
+	    perror("fork");
+	    exit(1);
+	case 0:
+	    close(fd[1]);
+	    for (;;) {
+		i = read(fd[0], buf, 256); /* any small size should do */
+		if (i == 0) break;
+		if (i < 0) { perror("read"); exit(1); }
+	    }
+	    exit(0);
+	default:
+	    break;
+    }
+
+    close(fd[0]);
+    memset(buf, 0, sizeof buf);
+    for (i = 0; i < 1000; i++) write_frame(fd[1], buf, sizeof buf);
+    exit(0);
+}