pipefs: prepare pipefs_open for named pipe support

kernel-src/fs/pipefs.c

@@ -17,23 +17,6 @@ static uintmax_t currentinode;
 
 static vops_t vnops;
 
-int pipefs_open(vnode_t **node, int flags, cred_t *cred) {
-	VOP_LOCK(*node);
-
-	pipenode_t *pipenode = (pipenode_t *)(*node);
-
-	if (flags & V_FFLAGS_READ) {
-		++pipenode->readers;
-	}
-
-	if (flags & V_FFLAGS_WRITE) {
-		++pipenode->writers;
-	}
-
-	VOP_UNLOCK(*node);
-	return 0;
-}
-
 int pipefs_close(vnode_t *node, int flags, cred_t *cred) {
 	VOP_LOCK(node);
 	pipenode_t *pipenode = (pipenode_t *)node;
@@ -56,6 +39,64 @@ int pipefs_close(vnode_t *node, int flags, cred_t *cred) {
 	return 0;
 }
 
+int pipefs_open(vnode_t **node, int flags, cred_t *cred) {
+	if ((flags & (V_FFLAGS_WRITE | V_FFLAGS_READ)) == 0)
+		return EINVAL;
+
+	VOP_LOCK(*node);
+	pipenode_t *pipenode = (pipenode_t *)(*node);
+
+	if (flags & V_FFLAGS_READ) {
+		++pipenode->readers;
+	}
+
+	if (flags & V_FFLAGS_WRITE) {
+		++pipenode->writers;
+	}
+
+	int error = 0;
+
+	if (pipenode->writers > 0 && pipenode->readers > 0)
+		goto leave;
+
+	if (flags & V_FFLAGS_NONBLOCKING) {
+		if (flags & V_FFLAGS_READ) {
+			goto leave;
+		} else if (flags & V_FFLAGS_WRITE) {
+			error = ENXIO;
+			goto leave;
+		}
+	}
+
+	// from this point on, flags has only one of V_FFLAGS_READ or V_FFLAGS_WRITE
+	// and there are either no writers or no readers.
+	eventlistener_t listener;
+	EVENT_INITLISTENER(&listener);
+	EVENT_ATTACH(&listener, &pipenode->openevent);
+
+	while (1) {
+		VOP_UNLOCK(*node);
+		error = EVENT_WAIT(&listener, 0);
+		VOP_LOCK(*node);
+
+		if (error || (pipenode->writers > 0 && pipenode->readers > 0))
+			break;
+	}
+
+	EVENT_DETACHALL(&listener);
+
+	leave:
+	if (error) {
+		VOP_UNLOCK(*node);
+		pipefs_close(*node, flags, cred);
+	} else {
+		EVENT_SIGNAL(&pipenode->openevent);
+		VOP_UNLOCK(*node);
+	}
+
+	return error;
+}
+
 // TODO for pipefs_read and pipefs_write, the return actually depends on how much data is in the pipe
 static int internalpoll(vnode_t *node, polldata_t *data, int events) {
 	pipenode_t *pipenode = (pipenode_t *)node;
@@ -333,6 +374,7 @@ static void ctor(scache_t *cache, void *obj) {
 	VOP_INIT(&node->vnode, &vnops, 0, V_TYPE_FIFO, NULL);
 	node->attr.inode = ++currentinode;
 	POLL_INITHEADER(&node->pollheader);
+	EVENT_INITHEADER(&node->openevent);
 }
 
 void pipefs_init() {

kernel-src/include/kernel/pipefs.h

@@ -5,6 +5,7 @@
 #include <ringbuffer.h>
 #include <semaphore.h>
 #include <kernel/poll.h>
+#include <kernel/event.h>
 
 typedef struct pipenode_t {
 	vnode_t vnode;
@@ -12,6 +13,7 @@ typedef struct pipenode_t {
 	ringbuffer_t data;
 	size_t readers, writers;
 	pollheader_t pollheader;
+	eventheader_t openevent;
 } pipenode_t;
 
 void pipefs_init();

kernel-src/sys/syscalls/pipe2.c

@@ -11,7 +11,7 @@ static void open(file_t *file, vnode_t *node, int flags) {
 	file->flags = flags;
 	file->offset = 0;
 	file->mode = 0777;
-	VOP_OPEN(&node, fileflagstovnodeflags(flags), &_cpu()->thread->proc->cred);
+	VOP_OPEN(&node, fileflagstovnodeflags(flags) | V_FFLAGS_NONBLOCKING, &_cpu()->thread->proc->cred);
 }
 
 syscallret_t syscall_pipe2(context_t *, int flags) {