Commit dd01e935 authored by Jim Harris's avatar Jim Harris
Browse files

nbd: use pthread_create instead of fork 



Using pthread_create is much cleaner, and avoids race
conditions related to the forked process sharing memory
with the primary process.  Specifically this fixes
a double spdk_event_call() of the shutdown event - one
from each process.  The primary process may have already
recycled the shutdown event, and when the forked process
calls it again, hilarity ensues.

Signed-off-by: default avatarJim Harris <james.r.harris@intel.com>
Change-Id: I3e4b77b8b380a8fa0227b770758099bcee0ef35b

Reviewed-on: https://review.gerrithub.io/388520


Reviewed-by: default avatarDaniel Verkamp <daniel.verkamp@intel.com>
Tested-by: default avatarSPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: default avatarBen Walker <benjamin.walker@intel.com>
parent 1517ed37

lib/nbd/nbd.c

+13 −23
Original line number Diff line number Diff line
@@ -350,19 +350,20 @@ spdk_nbd_poll(struct spdk_nbd_disk *nbd) 
	return 0;

}



static void

nbd_start_kernel(struct spdk_nbd_disk *nbd)

static void *

nbd_start_kernel(void *arg)

{

	struct spdk_nbd_disk *nbd = arg;

	int rc;

	char buf[64];



	close(nbd->spdk_sp_fd);

	spdk_unaffinitize_thread();



	rc = ioctl(nbd->dev_fd, NBD_SET_SOCK, nbd->kernel_sp_fd);

	if (rc == -1) {

		spdk_strerror_r(errno, buf, sizeof(buf));

		SPDK_ERRLOG("ioctl(NBD_SET_SOCK) failed: %s\n", buf);

		exit(-1);

		pthread_exit(NULL);

	}



#ifdef NBD_FLAG_SEND_TRIM
@@ -370,23 +371,22 @@ nbd_start_kernel(struct spdk_nbd_disk *nbd) 
	if (rc == -1) {

		spdk_strerror_r(errno, buf, sizeof(buf));

		SPDK_ERRLOG("ioctl(NBD_SET_FLAGS) failed: %s\n", buf);

		exit(-1);

		pthread_exit(NULL);

	}

#endif



	/* This will block in the kernel until the client disconnects. */

	/* This will block in the kernel until we close the spdk_sp_fd. */

	ioctl(nbd->dev_fd, NBD_DO_IT);



	ioctl(nbd->dev_fd, NBD_CLEAR_QUE);

	ioctl(nbd->dev_fd, NBD_CLEAR_SOCK);



	exit(0);

	pthread_exit(NULL);

}



struct spdk_nbd_disk *

spdk_nbd_start(struct spdk_bdev *bdev, const char *nbd_path)

{

	struct spdk_nbd_disk	*nbd;

	pthread_t		tid;

	int			rc;

	int			sp[2];

	char			buf[64];
@@ -448,23 +448,13 @@ spdk_nbd_start(struct spdk_bdev *bdev, const char *nbd_path) 


	printf("Enabling kernel access to bdev %s via %s\n", spdk_bdev_get_name(bdev), nbd_path);



	rc = fork();



	switch (rc) {

	case 0:

		nbd_start_kernel(nbd);

		break;

	case -1:

		spdk_strerror_r(errno, buf, sizeof(buf));

		SPDK_ERRLOG("could not fork: %s\n", buf);

	rc = pthread_create(&tid, NULL, &nbd_start_kernel, nbd);

	if (rc != 0) {

		spdk_strerror_r(rc, buf, sizeof(buf));

		SPDK_ERRLOG("could not create thread: %s\n", buf);

		goto err;

	default:

		close(nbd->dev_fd);

		break;

	}



	close(nbd->kernel_sp_fd);



	fcntl(nbd->spdk_sp_fd, F_SETFL, O_NONBLOCK);



	to_be32(&nbd->io.resp.magic, NBD_REPLY_MAGIC);