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nbd: use pthread_create instead of fork

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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: Jim Harris <james.r.harris@intel.com>
Change-Id: I3e4b77b8b380a8fa0227b770758099bcee0ef35b

Reviewed-on: https://review.gerrithub.io/388520
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
This commit is contained in:
Jim Harris 2017-11-21 12:52:37 -07:00
parent 1517ed376d
commit dd01e9353d
1 changed files with 13 additions and 23 deletions
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36
lib/nbd/nbd.c
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@ -350,19 +350,20 @@ spdk_nbd_poll(struct spdk_nbd_disk *nbd)
return 0; return 0;
} }
static void static void *
nbd_start_kernel(struct spdk_nbd_disk *nbd) nbd_start_kernel(void *arg)
{ {
struct spdk_nbd_disk *nbd = arg;
int rc; int rc;
char buf[64]; char buf[64];
close(nbd->spdk_sp_fd); spdk_unaffinitize_thread();
rc = ioctl(nbd->dev_fd, NBD_SET_SOCK, nbd->kernel_sp_fd); rc = ioctl(nbd->dev_fd, NBD_SET_SOCK, nbd->kernel_sp_fd);
if (rc == -1) { if (rc == -1) {
spdk_strerror_r(errno, buf, sizeof(buf)); spdk_strerror_r(errno, buf, sizeof(buf));
SPDK_ERRLOG("ioctl(NBD_SET_SOCK) failed: %s\n", buf); SPDK_ERRLOG("ioctl(NBD_SET_SOCK) failed: %s\n", buf);
exit(-1); pthread_exit(NULL);
} }
#ifdef NBD_FLAG_SEND_TRIM #ifdef NBD_FLAG_SEND_TRIM
@ -370,23 +371,22 @@ nbd_start_kernel(struct spdk_nbd_disk *nbd)
if (rc == -1) { if (rc == -1) {
spdk_strerror_r(errno, buf, sizeof(buf)); spdk_strerror_r(errno, buf, sizeof(buf));
SPDK_ERRLOG("ioctl(NBD_SET_FLAGS) failed: %s\n", buf); SPDK_ERRLOG("ioctl(NBD_SET_FLAGS) failed: %s\n", buf);
exit(-1); pthread_exit(NULL);
} }
#endif #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_DO_IT);
ioctl(nbd->dev_fd, NBD_CLEAR_QUE); ioctl(nbd->dev_fd, NBD_CLEAR_QUE);
ioctl(nbd->dev_fd, NBD_CLEAR_SOCK); ioctl(nbd->dev_fd, NBD_CLEAR_SOCK);
pthread_exit(NULL);
exit(0);
} }
struct spdk_nbd_disk * struct spdk_nbd_disk *
spdk_nbd_start(struct spdk_bdev *bdev, const char *nbd_path) spdk_nbd_start(struct spdk_bdev *bdev, const char *nbd_path)
{ {
struct spdk_nbd_disk *nbd; struct spdk_nbd_disk *nbd;
pthread_t tid;
int rc; int rc;
int sp[2]; int sp[2];
char buf[64]; 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); printf("Enabling kernel access to bdev %s via %s\n", spdk_bdev_get_name(bdev), nbd_path);
rc = fork(); rc = pthread_create(&tid, NULL, &nbd_start_kernel, nbd);
if (rc != 0) {
switch (rc) { spdk_strerror_r(rc, buf, sizeof(buf));
case 0: SPDK_ERRLOG("could not create thread: %s\n", buf);
nbd_start_kernel(nbd);
break;
case -1:
spdk_strerror_r(errno, buf, sizeof(buf));
SPDK_ERRLOG("could not fork: %s\n", buf);
goto err; goto err;
default:
close(nbd->dev_fd);
break;
} }
close(nbd->kernel_sp_fd);
fcntl(nbd->spdk_sp_fd, F_SETFL, O_NONBLOCK); fcntl(nbd->spdk_sp_fd, F_SETFL, O_NONBLOCK);
to_be32(&nbd->io.resp.magic, NBD_REPLY_MAGIC); to_be32(&nbd->io.resp.magic, NBD_REPLY_MAGIC);