Syslinux - Mar 2013 - Makefile race condition with parallel make

When attempting to build syslinux in parallel (make -j5), I encountered
the following error at the end:

rm -f liblpxelinux.a
ar cq liblpxelinux.a rawcon.o ./fs/pxe/dhcp_option.o ./fs/pxe/pxe.o
./fs/pxe/tftp.o ./fs/pxe/urlparse.o ./lwip/src/netif/ethernetif.o
./lwip/src/netif/etharp.o ./lwip/src/netif/slipif.o ./lwip/src/netif/ppp/md5.o
./lwip/src/netif/ppp/randm.o ./lwip/src/netif/ppp/chpms.o
./lwip/src/netif/ppp/lcp.o ./lwip/src/netif/ppp/vj.o ./lwip/src/netif/ppp/chap.o
./lwip/src/netif/ppp/ipcp.o ./lwip/src/netif/ppp/auth.o
./lwip/src/netif/ppp/fsm.o ./lwip/src/netif/ppp/ppp.o ./lwip/src/netif/ppp/pap.o
./lwip/src/netif/ppp/magic.o ./lwip/src/netif/ppp/ppp_oe.o
./lwip/src/netif/undiif.o ./lwip/src/core/init.o ./lwip/src/core/mem.o
./lwip/src/core/snmp/mib_structs.o ./lwip/src/core/snmp/asn1_dec.o
./lwip/src/core/snmp/asn1_enc.o ./lwip/src/core/snmp/msg_out.o
./lwip/src/core/snmp/mib2.o ./lwip/src/core/snmp/msg_in.o ./lwip/src/core/def.o
./lwip/src/core/dns.o ./lwip/src/core/sys.o ./lwip/src/core/dhcp.o
./lwip/src/core/ipv4/inet_chksum.o ./lwip/src/core/ipv4/icmp.o
./lwip/src/core/ipv4/autoip.o ./lwip/src/core/ipv4/ip_addr.o
./lwip/src/core/ipv4/inet.o ./lwip/src/core/ipv4/igmp.o
./lwip/src/core/ipv4/ip_frag.o ./lwip/src/core/ipv4/ip.o ./lwip/src/core/udp.o
./lwip/src/core/stats.o ./lwip/src/core/raw.o ./lwip/src/core/tcp.o
./lwip/src/core/netif.o ./lwip/src/core/memp.o ./lwip/src/core/timers.o
./lwip/src/core/pbuf.o ./lwip/src/core/tcp_in.o ./lwip/src/core/tcp_out.o
./lwip/src/api/api_lib.o ./lwip/src/api/netdb.o ./lwip/src/api/tcpip.o
./lwip/src/api/err.o ./lwip/src/api/sockets.o ./lwip/src/api/netifapi.o
./lwip/src/api/netbuf.o ./lwip/src/api/api_msg.o ./lwip/src/arch/sys_arch.o
./fs/pxe/core.o ./fs/pxe/dnsresolv.o ./fs/pxe/ftp.o ./fs/pxe/ftp_readdir.o
./fs/pxe/gpxeurl.o ./fs/pxe/http.o ./fs/pxe/http_readdir.o ./fs/pxe/idle.o
./fs/pxe/isr.o ./fs/pxe/tcp.o
ar: ./fs/pxe/dhcp_option.o: No such file or directory
make[1]: *** [liblpxelinux.a] Error 1

Scanning back through the build log showed that earlier in the build it
built fs/pxe/dhcp_option.o, added it to libpxelinux.a, and then deleted
it.

Looking at core/Makefile shows the race, introduced in commit
16aa878d78086e9bc1c1f1053dc24da295f81e05:

# Legacy network stack
libpxelinux.a: rawcon.o $(PXELINUX_OBJS)
        rm -f $@
        $(AR) cq $@ $^
        $(RANLIB) $@
        rm $(PXELINUX_OBJS)

# LwIP network stack
liblpxelinux.a: rawcon.o
        $(MAKE) CFLAGS="$(CFLAGS) -DIS_LPXELINUX" $(LPXELINUX_OBJS)
        rm -f $@
        $(AR) cq $@ $^ $(LPXELINUX_OBJS)
        $(RANLIB) $@
        rm $(LPXELINUX_OBJS)

PXELINUX_OBJS and LPXELINUX_OBJS contain some common objects, namely
those in CORE_PXE_CSRC:

CORE_PXE_CSRC = \
        $(addprefix ./fs/pxe/, dhcp_option.c pxe.c tftp.c urlparse.c)

So, if those two rules run in parallel, they'll step on each other.
Since they both need to build using different build flags, they need to
produce different object files; each library can then depend on the
corresponding object files (dropping the $(MAKE) from liblpxelinux.a),
and they can stop removing each others' objects.

- Josh Triplett

I think this patch should disentangle the dependencies by avoiding the
need for IS_LPXELINUX.

Please let me know if it works for you.

	-hpa

-------------- next part --------------
diff --git a/core/Makefile b/core/Makefile
index 1890b24..59a61eb 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -138,15 +138,12 @@ libpxelinux.a: rawcon.o $(PXELINUX_OBJS)
 	rm -f $@
 	$(AR) cq $@ $^
 	$(RANLIB) $@
-	rm $(PXELINUX_OBJS)
 
 # LwIP network stack
-liblpxelinux.a: rawcon.o
-	$(MAKE) CFLAGS="$(CFLAGS) -DIS_LPXELINUX" $(LPXELINUX_OBJS)
+liblpxelinux.a: rawcon.o $(LPXELINUX_OBJS)
 	rm -f $@
-	$(AR) cq $@ $^ $(LPXELINUX_OBJS)
+	$(AR) cq $@ $^
 	$(RANLIB) $@
-	rm $(LPXELINUX_OBJS)
 
 libldlinux.a: plaincon.o
 	rm -f $@
diff --git a/core/fs/pxe/core.c b/core/fs/pxe/core.c
index 9246f66..e330ba8 100644
--- a/core/fs/pxe/core.c
+++ b/core/fs/pxe/core.c
@@ -6,6 +6,13 @@
 #include <net.h>
 #include "pxe.h"
 
+const struct url_scheme url_schemes[] = {
+    { "tftp", tftp_open, 0 },
+    { "http", http_open, O_DIRECTORY },
+    { "ftp",  ftp_open,  O_DIRECTORY },
+    { NULL, NULL, 0 },
+};
+
 /**
  * Open a socket
  *
@@ -16,7 +23,7 @@
  */
 int net_core_open(struct pxe_pvt_inode *socket, enum net_core_proto proto)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_lwip *priv = &socket->net.lwip;
     enum netconn_type type;
     int err;
 
@@ -53,7 +60,7 @@ int net_core_open(struct pxe_pvt_inode *socket, enum
net_core_proto proto)
  */
 void net_core_close(struct pxe_pvt_inode *socket)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_lwip *priv = &socket->net.lwip;
 
     if (priv->conn) {
 	netconn_delete(priv->conn);
@@ -71,7 +78,7 @@ void net_core_close(struct pxe_pvt_inode *socket)
 void net_core_connect(struct pxe_pvt_inode *socket, uint32_t ip,
 		      uint16_t port)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_lwip *priv = &socket->net.lwip;
     struct ip_addr addr;
 
     addr.addr = ip;
@@ -85,7 +92,7 @@ void net_core_connect(struct pxe_pvt_inode *socket, uint32_t
ip,
  */
 void net_core_disconnect(struct pxe_pvt_inode *socket)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_lwip *priv = &socket->net.lwip;
     netconn_disconnect(priv->conn);
 }
 
@@ -102,7 +109,7 @@ void net_core_disconnect(struct pxe_pvt_inode *socket)
 int net_core_recv(struct pxe_pvt_inode *socket, void *buf, uint16_t *buf_len,
 		  uint32_t *src_ip, uint16_t *src_port)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_lwip *priv = &socket->net.lwip;
     struct netbuf *nbuf;
     u16_t nbuf_len;
     int err;
@@ -138,7 +145,7 @@ int net_core_recv(struct pxe_pvt_inode *socket, void *buf,
uint16_t *buf_len,
  */
 void net_core_send(struct pxe_pvt_inode *socket, const void *data, size_t len)
 {
-    struct netconn *conn = socket->private.conn;
+    struct netconn *conn = socket->net.lwip.conn;
     struct netbuf *nbuf;
     void *pbuf;
     int err;
diff --git a/core/fs/pxe/ftp.c b/core/fs/pxe/ftp.c
index 5d5a6f0..c2d155a 100644
--- a/core/fs/pxe/ftp.c
+++ b/core/fs/pxe/ftp.c
@@ -69,7 +69,7 @@ static int ftp_cmd_response(struct inode *inode, const char
*cmd,
 	*q++ = '\n';
 	cmd_len += 2;
 
-	err = netconn_write(socket->private.conn, cmd_buf, cmd_len, NETCONN_COPY);
+	err = netconn_write(socket->net.lwip.conn, cmd_buf, cmd_len, NETCONN_COPY);
 	if (err)
 	    return -1;
     }
@@ -166,7 +166,7 @@ static void ftp_close_file(struct inode *inode)
     int resp;
 
     ctlsock = socket->ctl ? PVT(socket->ctl) : NULL;
-    if (ctlsock->private.conn) {
+    if (ctlsock->net.lwip.conn) {
 	resp = ftp_cmd_response(socket->ctl, "QUIT", NULL, NULL, NULL);
 	while (resp == 226) {
 	    resp = ftp_cmd_response(socket->ctl, NULL, NULL, NULL, NULL);
@@ -209,11 +209,11 @@ void ftp_open(struct url_info *url, int flags, struct
inode *inode,
 	return;
     ctlsock = PVT(socket->ctl);
     ctlsock->ops = &tcp_conn_ops; /* The control connection is just TCP
*/
-    ctlsock->private.conn = netconn_new(NETCONN_TCP);
-    if (!ctlsock->private.conn)
+    ctlsock->net.lwip.conn = netconn_new(NETCONN_TCP);
+    if (!ctlsock->net.lwip.conn)
 	goto err_free;
     addr.addr = url->ip;
-    err = netconn_connect(ctlsock->private.conn, &addr, url->port);
+    err = netconn_connect(ctlsock->net.lwip.conn, &addr, url->port);
     if (err)
 	goto err_delete;
 
@@ -248,10 +248,10 @@ void ftp_open(struct url_info *url, int flags, struct
inode *inode,
     if (resp != 227 || pasv_bytes != 6)
 	goto err_disconnect;
 
-    socket->private.conn = netconn_new(NETCONN_TCP);
-    if (!socket->private.conn)
+    socket->net.lwip.conn = netconn_new(NETCONN_TCP);
+    if (!socket->net.lwip.conn)
 	goto err_disconnect;
-    err = netconn_connect(socket->private.conn, (struct ip_addr
*)&pasv_data[0],
+    err = netconn_connect(socket->net.lwip.conn, (struct ip_addr
*)&pasv_data[0],
 			  ntohs(*(uint16_t *)&pasv_data[4]));
     if (err)
 	goto err_disconnect;
@@ -266,15 +266,15 @@ void ftp_open(struct url_info *url, int flags, struct
inode *inode,
     return;			/* Sucess! */
 
 err_disconnect:
-    if (ctlsock->private.conn)
-	netconn_write(ctlsock->private.conn, "QUIT\r\n", 6,
NETCONN_NOCOPY);
-    if (socket->private.conn)
-	netconn_delete(socket->private.conn);
-    if (ctlsock->private.buf)
-	netbuf_delete(ctlsock->private.buf);
+    if (ctlsock->net.lwip.conn)
+	netconn_write(ctlsock->net.lwip.conn, "QUIT\r\n", 6,
NETCONN_NOCOPY);
+    if (socket->net.lwip.conn)
+	netconn_delete(socket->net.lwip.conn);
+    if (ctlsock->net.lwip.buf)
+	netbuf_delete(ctlsock->net.lwip.buf);
 err_delete:
-    if (ctlsock->private.conn)
-	netconn_delete(ctlsock->private.conn);
+    if (ctlsock->net.lwip.conn)
+	netconn_delete(ctlsock->net.lwip.conn);
 err_free:
     free_socket(socket->ctl);
 }
diff --git a/core/fs/pxe/http.c b/core/fs/pxe/http.c
index 9bf0c92..94f1059 100644
--- a/core/fs/pxe/http.c
+++ b/core/fs/pxe/http.c
@@ -191,8 +191,8 @@ void http_open(struct url_info *url, int flags, struct inode
*inode,
     inode->size = content_length = -1;
 
     /* Start the http connection */
-    socket->private.conn = netconn_new(NETCONN_TCP);
-    if (!socket->private.conn) {
+    socket->net.lwip.conn = netconn_new(NETCONN_TCP);
+    if (!socket->net.lwip.conn) {
 	printf("netconn_new failed\n");
         return;
     }
@@ -201,7 +201,7 @@ void http_open(struct url_info *url, int flags, struct inode
*inode,
     if (!url->port)
 	url->port = HTTP_PORT;
 
-    err = netconn_connect(socket->private.conn, &addr, url->port);
+    err = netconn_connect(socket->net.lwip.conn, &addr, url->port);
     if (err) {
 	printf("netconn_connect error %d\n", err);
 	goto fail;
@@ -225,7 +225,7 @@ void http_open(struct url_info *url, int flags, struct inode
*inode,
     if (header_bytes >= header_len)
 	goto fail;		/* Buffer overflow */
 
-    err = netconn_write(socket->private.conn, header_buf,
+    err = netconn_write(socket->net.lwip.conn, header_buf,
 			header_bytes, NETCONN_NOCOPY);
     if (err) {
 	printf("netconn_write error %d\n", err);
diff --git a/core/fs/pxe/pxe.c b/core/fs/pxe/pxe.c
index 4d694a1..3f68e96 100644
--- a/core/fs/pxe/pxe.c
+++ b/core/fs/pxe/pxe.c
@@ -29,20 +29,6 @@ static bool has_gpxe;
 static uint32_t gpxe_funcs;
 bool have_uuid = false;
 
-static struct url_scheme {
-    const char *name;
-    void (*open)(struct url_info *, int, struct inode *, const char **);
-    int ok_flags;
-} url_schemes[] = {
-    { "tftp", tftp_open, 0 },
-#ifdef IS_LPXELINUX
-    { "http", http_open, O_DIRECTORY },
-    { "ftp",  ftp_open,  O_DIRECTORY },
-#endif
-    { NULL, NULL, 0 },
-};
-#define OK_FLAGS_MASK	(O_DIRECTORY|O_WRONLY)
-
 /*
  * Allocate a local UDP port structure and assign it a local port number.
  * Return the inode pointer if success, or null if failure
diff --git a/core/fs/pxe/pxe.h b/core/fs/pxe/pxe.h
index 2d4be3b..68d4e3e 100644
--- a/core/fs/pxe/pxe.h
+++ b/core/fs/pxe/pxe.h
@@ -21,6 +21,7 @@
 #define PXE_H
 
 #include <syslinux/pxe_api.h>
+#include <fcntl.h>		/* For OK_FLAGS_MASK */
 #include "fs.h"			/* Mostly for FILENAME_MAX */
 
 /*
@@ -114,19 +115,19 @@ struct pxe_conn_ops {
     int (*readdir)(struct inode *inode, struct dirent *dirent);
 };    
 
-struct net_private {
-#ifdef IS_LPXELINUX
-    struct netconn *conn;      /* lwip network connection */
-    struct netbuf *buf;	       /* lwip cached buffer */
-#else
-    uint16_t tftp_localport;   /* Local port number  (0=not in use) */
-    uint32_t tftp_remoteip;    /* Remote IP address (0 = disconnected) */
-#endif
-
+union net_private {
+    struct net_private_lwip {
+	struct netconn *conn;      /* lwip network connection */
+	struct netbuf *buf;	   /* lwip cached buffer */
+    } lwip;
+    struct net_private_tftp {
+	uint32_t remoteip;  	  /* Remote IP address (0 = disconnected) */
+	uint16_t localport;   	  /* Local port number  (0=not in use) */
+    } tftp;
 };
 
 struct pxe_pvt_inode {
-    struct net_private private;   /* Network stack private data */
+    union net_private net;	  /* Network stack private data */
     uint16_t tftp_remoteport;     /* Remote port number */
     uint32_t tftp_filepos;        /* bytes downloaded (including buffer) */
     uint32_t tftp_blksize;        /* Block size for this connection(*) */
@@ -185,6 +186,17 @@ extern bool have_uuid;
 extern uint8_t uuid_type;
 extern uint8_t uuid[];
 
+struct url_info;
+struct url_scheme {
+    const char *name;
+    void (*open)(struct url_info *, int, struct inode *, const char **);
+    int ok_flags;
+};
+/* Flags which can be specified in url_scheme.ok_flags */
+#define OK_FLAGS_MASK	(O_DIRECTORY|O_WRONLY)
+
+extern const struct url_scheme url_schemes[];
+
 /*
  * Compute the suitable gateway for a specific route -- too many
  * vendor PXE stacks don't do this correctly...
diff --git a/core/fs/pxe/tcp.c b/core/fs/pxe/tcp.c
index 528fbce..9076197 100644
--- a/core/fs/pxe/tcp.c
+++ b/core/fs/pxe/tcp.c
@@ -25,13 +25,13 @@ void tcp_close_file(struct inode *inode)
 {
     struct pxe_pvt_inode *socket = PVT(inode);
 
-    if (socket->private.conn) {
-	netconn_delete(socket->private.conn);
-	socket->private.conn = NULL;
+    if (socket->net.lwip.conn) {
+	netconn_delete(socket->net.lwip.conn);
+	socket->net.lwip.conn = NULL;
     }
-    if (socket->private.buf) {
-	netbuf_delete(socket->private.buf);
-        socket->private.buf = NULL;
+    if (socket->net.lwip.buf) {
+	netbuf_delete(socket->net.lwip.buf);
+        socket->net.lwip.buf = NULL;
     }
 }
 
@@ -43,16 +43,16 @@ void tcp_fill_buffer(struct inode *inode)
     err_t err;
 
     /* Clean up or advance an inuse netbuf */
-    if (socket->private.buf) {
-	if (netbuf_next(socket->private.buf) < 0) {
-	    netbuf_delete(socket->private.buf);
-	    socket->private.buf = NULL;
+    if (socket->net.lwip.buf) {
+	if (netbuf_next(socket->net.lwip.buf) < 0) {
+	    netbuf_delete(socket->net.lwip.buf);
+	    socket->net.lwip.buf = NULL;
 	}
     }
     /* If needed get a new netbuf */
-    if (!socket->private.buf) {
-	err = netconn_recv(socket->private.conn, &(socket->private.buf));
-	if (!socket->private.buf || err) {
+    if (!socket->net.lwip.buf) {
+	err = netconn_recv(socket->net.lwip.conn, &(socket->net.lwip.buf));
+	if (!socket->net.lwip.buf || err) {
 	    socket->tftp_goteof = 1;
 	    if (inode->size == -1)
 		inode->size = socket->tftp_filepos;
@@ -61,7 +61,7 @@ void tcp_fill_buffer(struct inode *inode)
 	}
     }
     /* Report the current fragment of the netbuf */
-    err = netbuf_data(socket->private.buf, &data, &len);
+    err = netbuf_data(socket->net.lwip.buf, &data, &len);
     if (err) {
 	printf("netbuf_data err: %d\n", err);
 	kaboom();
diff --git a/core/legacynet/core.c b/core/legacynet/core.c
index 2163c69..848410c 100644
--- a/core/legacynet/core.c
+++ b/core/legacynet/core.c
@@ -11,6 +11,11 @@ static __lowmem char packet_buf[PKTBUF_SIZE] __aligned(16);
 extern uint16_t get_port(void);
 extern void free_port(uint16_t);
 
+const struct url_scheme url_schemes[] = {
+    { "tftp", tftp_open, 0 },
+    { NULL, NULL, 0 }
+};
+
 /**
  * Open a socket
  *
@@ -22,14 +27,14 @@ extern void free_port(uint16_t);
 int net_core_open(struct pxe_pvt_inode *socket __unused,
 		  enum net_core_proto proto)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_tftp *priv = &socket->net.tftp;
 
     /* The legacy stack only supports UDP */
     if (proto != NET_CORE_UDP)
 	return -1;
 
     /* Allocate local UDP port number */
-    priv->tftp_localport = get_port();
+    priv->localport = get_port();
 
     return 0;
 }
@@ -41,10 +46,10 @@ int net_core_open(struct pxe_pvt_inode *socket __unused,
  */
 void net_core_close(struct pxe_pvt_inode *socket)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_tftp *priv = &socket->net.tftp;
 
-    if (priv->tftp_localport)
-	free_port(priv->tftp_localport);
+    if (priv->localport)
+	free_port(priv->localport);
 }
 
 /**
@@ -57,10 +62,10 @@ void net_core_close(struct pxe_pvt_inode *socket)
 void net_core_connect(struct pxe_pvt_inode *socket, uint32_t ip,
 		      uint16_t port)
 {
-    struct net_private *priv = &socket->private;
+    struct net_private_tftp *priv = &socket->net.tftp;
 
     socket->tftp_remoteport = htons(port);
-    priv->tftp_remoteip = ip;
+    priv->remoteip = ip;
 
 }
 
@@ -87,7 +92,7 @@ int net_core_recv(struct pxe_pvt_inode *socket, void *buf,
uint16_t *buf_len,
 		  uint32_t *src_ip, uint16_t *src_port)
 {
     static __lowmem struct s_PXENV_UDP_READ  udp_read;
-    struct net_private *priv = &socket->private;
+    struct net_private_tftp *priv = &socket->net.tftp;
     uint16_t bytes;
     int err;
 
@@ -95,7 +100,7 @@ int net_core_recv(struct pxe_pvt_inode *socket, void *buf,
uint16_t *buf_len,
     udp_read.buffer      = FAR_PTR(packet_buf);
     udp_read.buffer_size = PKTBUF_SIZE;
     udp_read.dest_ip     = IPInfo.myip;
-    udp_read.d_port      = priv->tftp_localport;
+    udp_read.d_port      = priv->localport;
 
     err = pxe_call(PXENV_UDP_READ, &udp_read);
     if (err)
@@ -124,7 +129,7 @@ int net_core_recv(struct pxe_pvt_inode *socket, void *buf,
uint16_t *buf_len,
 void net_core_send(struct pxe_pvt_inode *socket, const void *data, size_t len)
 {
     static __lowmem struct s_PXENV_UDP_WRITE udp_write;
-    struct net_private *priv = &socket->private;
+    struct net_private_tftp *priv = &socket->net.tftp;
     void *lbuf;
     uint16_t tid;
 
@@ -134,9 +139,9 @@ void net_core_send(struct pxe_pvt_inode *socket, const void
*data, size_t len)
 
     memcpy(lbuf, data, len);
 
-    tid = priv->tftp_localport;   /* TID(local port No) */
+    tid = priv->localport;   /* TID(local port No) */
     udp_write.buffer    = FAR_PTR(lbuf);
-    udp_write.ip        = priv->tftp_remoteip;
+    udp_write.ip        = priv->remoteip;
     udp_write.gw        = gateway(udp_write.ip);
     udp_write.src_port  = tid;
     udp_write.dst_port  = socket->tftp_remoteport;