[dpdk-dev] [PATCH v2 11/11] lib/librte_vhost: support dynamically registering vhost server
Tetsuya Mukawa
mukawa at igel.co.jp
Mon Feb 16 09:17:09 CET 2015
On 2015/02/12 14:07, Huawei Xie wrote:
> * support calling rte_vhost_driver_register after rte_vhost_driver_session_start
> * add mutext to protect fdset from concurrent access
> * add busy flag in fdentry. this flag is set before cb and cleared after cb is finished.
>
> mutex lock scenario in vhost:
>
> * event_dispatch(in rte_vhost_driver_session_start) runs in a seperate thread, infinitely
> processing vhost messages through cb(callback).
> * event_dispatch acquires the lock, get the cb and its context, mark the busy flag,
> and releases the mutex.
> * vserver_new_vq_conn cb calls fdset_add, which acquires the mutex and add new fd into fdset.
> * vserver_message_handler cb frees data context, marks remove flag to request to delete
> connfd(connection fd) from fdset.
> * after cb returns, event_dispatch
> 1. clears busy flag.
> 2. if there is remove request, call fdset_del, which acquires mutex, checks busy flag, and
> removes connfd from fdset.
> * rte_vhost_driver_unregister(not implemented) runs in another thread, acquires the mutex,
> calls fdset_del to remove fd(listenerfd) from fdset. Then it could free data context.
>
> The above steps ensures fd data context isn't freed when cb is using.
>
> VM(s) should have been shutdown before rte_vhost_driver_unregister.
>
> Signed-off-by: Huawei Xie <huawei.xie at intel.com>
> ---
> lib/librte_vhost/vhost_user/fd_man.c | 63 +++++++++++++++++++++++++---
> lib/librte_vhost/vhost_user/fd_man.h | 5 ++-
> lib/librte_vhost/vhost_user/vhost-net-user.c | 34 +++++++++------
> 3 files changed, 82 insertions(+), 20 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost_user/fd_man.c b/lib/librte_vhost/vhost_user/fd_man.c
> index 929fbc3..63ac4df 100644
> --- a/lib/librte_vhost/vhost_user/fd_man.c
> +++ b/lib/librte_vhost/vhost_user/fd_man.c
> @@ -40,6 +40,7 @@
> #include <sys/types.h>
> #include <unistd.h>
>
> +#include <rte_common.h>
> #include <rte_log.h>
>
> #include "fd_man.h"
> @@ -145,6 +146,8 @@ fdset_add(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat)
> if (pfdset == NULL || fd == -1)
> return -1;
>
> + pthread_mutex_lock(&pfdset->fd_mutex);
> +
> /* Find a free slot in the list. */
> i = fdset_find_free_slot(pfdset);
> if (i == -1)
> @@ -153,6 +156,8 @@ fdset_add(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat)
> fdset_add_fd(pfdset, i, fd, rcb, wcb, dat);
> pfdset->num++;
>
> + pthread_mutex_unlock(&pfdset->fd_mutex);
> +
> return 0;
> }
>
> @@ -164,17 +169,36 @@ fdset_del(struct fdset *pfdset, int fd)
> {
> int i;
>
> + if (pfdset == NULL || fd == -1)
> + return;
> +
> +again:
> + pthread_mutex_lock(&pfdset->fd_mutex);
> +
> i = fdset_find_fd(pfdset, fd);
> if (i != -1 && fd != -1) {
> + /* busy indicates r/wcb is executing! */
> + if (pfdset->fd[i].busy == 1) {
> + pthread_mutex_unlock(&pfdset->fd_mutex);
> + goto again;
> + }
> +
> pfdset->fd[i].fd = -1;
> pfdset->fd[i].rcb = pfdset->fd[i].wcb = NULL;
> pfdset->num--;
> }
> +
> + pthread_mutex_unlock(&pfdset->fd_mutex);
> }
>
> /**
> * This functions runs in infinite blocking loop until there is no fd in
> * pfdset. It calls corresponding r/w handler if there is event on the fd.
> + *
> + * Before the callback is called, we set the flag to busy status; If other
> + * thread(now rte_vhost_driver_unregister) calls fdset_del concurrently, it
> + * will wait until the flag is reset to zero(which indicates the callback is
> + * finished), then it could free the context after fdset_del.
> */
> void
> fdset_event_dispatch(struct fdset *pfdset)
> @@ -183,6 +207,10 @@ fdset_event_dispatch(struct fdset *pfdset)
> int i, maxfds;
> struct fdentry *pfdentry;
> int num = MAX_FDS;
> + fd_cb rcb, wcb;
> + void *dat;
> + int fd;
> + int remove1, remove2;
>
> if (pfdset == NULL)
> return;
> @@ -190,18 +218,41 @@ fdset_event_dispatch(struct fdset *pfdset)
> while (1) {
> FD_ZERO(&rfds);
> FD_ZERO(&wfds);
> + pthread_mutex_lock(&pfdset->fd_mutex);
> +
> maxfds = fdset_fill(&rfds, &wfds, pfdset);
> - if (maxfds == -1)
> - return;
> + if (maxfds == -1) {
> + pthread_mutex_unlock(&pfdset->fd_mutex);
> + sleep(1);
> + continue;
> + }
> +
> + pthread_mutex_unlock(&pfdset->fd_mutex);
>
> select(maxfds + 1, &rfds, &wfds, NULL, NULL);
>
> for (i = 0; i < num; i++) {
> + remove1 = remove2 = 0;
> + pthread_mutex_lock(&pfdset->fd_mutex);
> pfdentry = &pfdset->fd[i];
> - if (pfdentry->fd >= 0 && FD_ISSET(pfdentry->fd, &rfds) && pfdentry->rcb)
> - pfdentry->rcb(pfdentry->fd, pfdentry->dat);
> - if (pfdentry->fd >= 0 && FD_ISSET(pfdentry->fd, &wfds) && pfdentry->wcb)
> - pfdentry->wcb(pfdentry->fd, pfdentry->dat);
> + fd = pfdentry->fd;
> + rcb = pfdentry->rcb;
> + wcb = pfdentry->wcb;
> + dat = pfdentry->dat;
> + pfdentry->busy = 1;
> + pthread_mutex_unlock(&pfdset->fd_mutex);
> + if (fd >= 0 && FD_ISSET(fd, &rfds) && rcb)
> + rcb(fd, dat, &remove1);
> + if (fd >= 0 && FD_ISSET(fd, &wfds) && wcb)
> + wcb(fd, dat, &remove2);
Hi Xie,
Should we add pthread_mutex_lock() before accessing pfdentry->busy?
> + pfdentry->busy = 0;
Should we add pthread_mutex_unlock()?
Thanks,
Tetsuya
> + /*
> + * fdset_del needs to check busy flag.
> + * We don't allow fdset_del to be called in callback
> + * directly.
> + */
> + if (remove1 || remove2)
> + fdset_del(pfdset, fd);
> }
> }
> }
> diff --git a/lib/librte_vhost/vhost_user/fd_man.h b/lib/librte_vhost/vhost_user/fd_man.h
> index 26b4619..74ecde2 100644
> --- a/lib/librte_vhost/vhost_user/fd_man.h
> +++ b/lib/librte_vhost/vhost_user/fd_man.h
> @@ -34,20 +34,23 @@
> #ifndef _FD_MAN_H_
> #define _FD_MAN_H_
> #include <stdint.h>
> +#include <pthread.h>
>
> #define MAX_FDS 1024
>
> -typedef void (*fd_cb)(int fd, void *dat);
> +typedef void (*fd_cb)(int fd, void *dat, int *remove);
>
> struct fdentry {
> int fd; /* -1 indicates this entry is empty */
> fd_cb rcb; /* callback when this fd is readable. */
> fd_cb wcb; /* callback when this fd is writeable.*/
> void *dat; /* fd context */
> + int busy; /* whether this entry is being used in cb. */
> };
>
> struct fdset {
> struct fdentry fd[MAX_FDS];
> + pthread_mutex_t fd_mutex;
> int num; /* current fd number of this fdset */
> };
>
> diff --git a/lib/librte_vhost/vhost_user/vhost-net-user.c b/lib/librte_vhost/vhost_user/vhost-net-user.c
> index 634a498..3aa9436 100644
> --- a/lib/librte_vhost/vhost_user/vhost-net-user.c
> +++ b/lib/librte_vhost/vhost_user/vhost-net-user.c
> @@ -41,6 +41,7 @@
> #include <sys/socket.h>
> #include <sys/un.h>
> #include <errno.h>
> +#include <pthread.h>
>
> #include <rte_log.h>
> #include <rte_virtio_net.h>
> @@ -51,8 +52,9 @@
> #include "virtio-net-user.h"
>
> #define MAX_VIRTIO_BACKLOG 128
> -static void vserver_new_vq_conn(int fd, void *data);
> -static void vserver_message_handler(int fd, void *dat);
> +
> +static void vserver_new_vq_conn(int fd, void *data, int *remove);
> +static void vserver_message_handler(int fd, void *dat, int *remove);
> struct vhost_net_device_ops const *ops;
>
> struct connfd_ctx {
> @@ -61,10 +63,18 @@ struct connfd_ctx {
> };
>
> #define MAX_VHOST_SERVER 1024
> -static struct {
> +struct _vhost_server {
> struct vhost_server *server[MAX_VHOST_SERVER];
> - struct fdset fdset; /**< The fd list this vhost server manages. */
> -} g_vhost_server;
> + struct fdset fdset;
> +};
> +
> +static struct _vhost_server g_vhost_server = {
> + .fdset = {
> + .fd = { [0 ... MAX_FDS - 1] = {-1, NULL, NULL, NULL, 0} },
> + .fd_mutex = PTHREAD_MUTEX_INITIALIZER,
> + .num = 0
> + },
> +};
>
> static int vserver_idx;
>
> @@ -261,7 +271,7 @@ send_vhost_message(int sockfd, struct VhostUserMsg *msg)
>
> /* call back when there is new virtio connection. */
> static void
> -vserver_new_vq_conn(int fd, void *dat)
> +vserver_new_vq_conn(int fd, void *dat, __rte_unused int *remove)
> {
> struct vhost_server *vserver = (struct vhost_server *)dat;
> int conn_fd;
> @@ -304,7 +314,7 @@ vserver_new_vq_conn(int fd, void *dat)
>
> /* callback when there is message on the connfd */
> static void
> -vserver_message_handler(int connfd, void *dat)
> +vserver_message_handler(int connfd, void *dat, int *remove)
> {
> struct vhost_device_ctx ctx;
> struct connfd_ctx *cfd_ctx = (struct connfd_ctx *)dat;
> @@ -319,7 +329,7 @@ vserver_message_handler(int connfd, void *dat)
> "vhost read message failed\n");
>
> close(connfd);
> - fdset_del(&g_vhost_server.fdset, connfd);
> + *remove = 1;
> free(cfd_ctx);
> user_destroy_device(ctx);
> ops->destroy_device(ctx);
> @@ -330,7 +340,7 @@ vserver_message_handler(int connfd, void *dat)
> "vhost peer closed\n");
>
> close(connfd);
> - fdset_del(&g_vhost_server.fdset, connfd);
> + *remove = 1;
> free(cfd_ctx);
> user_destroy_device(ctx);
> ops->destroy_device(ctx);
> @@ -342,7 +352,7 @@ vserver_message_handler(int connfd, void *dat)
> "vhost read incorrect message\n");
>
> close(connfd);
> - fdset_del(&g_vhost_server.fdset, connfd);
> + *remove = 1;
> free(cfd_ctx);
> user_destroy_device(ctx);
> ops->destroy_device(ctx);
> @@ -426,10 +436,8 @@ rte_vhost_driver_register(const char *path)
> {
> struct vhost_server *vserver;
>
> - if (vserver_idx == 0) {
> - fdset_init(&g_vhost_server.fdset);
> + if (vserver_idx == 0)
> ops = get_virtio_net_callbacks();
> - }
> if (vserver_idx == MAX_VHOST_SERVER)
> return -1;
>
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