[sheepdog] [PATCH v1] sheep/cluster: use sema_t to replace pthread_cont_t

[Liu Yuan]

On Fri, Mar 28, 2014 at 04:58:57PM +0800, Robin Dong wrote:
> From: Robin Dong <sanbai at taobao.com>
> 
> In previous commit (52af6ff1aabe2f4f32e55e4a88537df41d4db7e9), we use
> pthread_cond_t instead of pthread_mutex_t to avoid panic, but the pthread_cont_t
> has its own problem: it may miss the wakeup-signal so we have to call
> sd_cond_wait_timeout() which will wakeup every n-seconds and waste some cpu.
> 
> Therefore, use sema_t is more neat since it is more suitable for P/V operations.
> 
> Signed-off-by: Robin Dong <sanbai at taobao.com>
> ---
>  sheep/cluster/zookeeper.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/sheep/cluster/zookeeper.c b/sheep/cluster/zookeeper.c
> index 3a72cb3..30a5f35 100644
> --- a/sheep/cluster/zookeeper.c
> +++ b/sheep/cluster/zookeeper.c
> @@ -16,6 +16,7 @@
>  #include <sys/epoll.h>
>  #include <zookeeper/zookeeper.h>
>  #include <pthread.h>
> +#include <semaphore.h>
>  
>  #include "cluster.h"
>  #include "config.h"
> @@ -42,8 +43,7 @@ struct cluster_lock {
>  	/* referenced by different threads in one sheepdog daemon */
>  	uint64_t ref;
>  	/* wait for the release of id by other lock owner */
> -	struct sd_cond wait_wakeup;
> -	struct sd_mutex wait_mutex;
> +	sem_t wait_wakeup;
>  	/* lock for different threads of the same node on the same id */
>  	struct sd_mutex id_lock;
>  	char lock_path[MAX_NODE_STR_LEN];
> @@ -315,7 +315,7 @@ static int lock_table_lookup_wakeup(uint64_t lock_id)
>  	sd_mutex_lock(table_locks + hval);
>  	hlist_for_each_entry(lock, iter, cluster_locks_table + hval, hnode) {
>  		if (lock->id == lock_id) {
> -			sd_cond_signal(&lock->wait_wakeup);
> +			sem_post(&lock->wait_wakeup);
>  			res = 0;
>  			break;
>  		}
> @@ -352,8 +352,7 @@ static struct cluster_lock *lock_table_lookup_acquire(uint64_t lock_id)
>  		if (rc)
>  			panic("Failed to init node %s", path);
>  
> -		sd_cond_init(&ret_lock->wait_wakeup);
> -		sd_init_mutex(&ret_lock->wait_mutex);
> +		sem_init(&ret_lock->wait_wakeup, 0, 1);
>  		sd_init_mutex(&ret_lock->id_lock);
>  
>  		hlist_add_head(&(ret_lock->hnode), cluster_locks_table + hval);
> @@ -398,8 +397,7 @@ static void lock_table_lookup_release(uint64_t lock_id)
>  			hlist_del(iter);
>  			/* free all resource used by this lock */
>  			sd_destroy_mutex(&lock->id_lock);
> -			sd_destroy_mutex(&lock->wait_mutex);
> -			sd_destroy_cond(&lock->wait_wakeup);
> +			sem_destroy(&lock->wait_wakeup);
>  			snprintf(path, MAX_NODE_STR_LEN, LOCK_ZNODE "/%"PRIu64,
>  				 lock->id);
>  			/*
> @@ -1267,7 +1265,7 @@ kick_block_event:
>   * This operation will create a seq-ephemeral znode in lock directory
>   * of zookeeper (use lock-id as dir name). The smallest file path in
>   * this directory wil be the owner of the lock; the other threads will
> - * wait on a struct sd_cond (cluster_lock->wait_wakeup)
> + * wait on a sem_t (cluster_lock->wait_wakeup)
>   */
>  static void zk_lock(uint64_t lock_id)
>  {
> @@ -1334,9 +1332,7 @@ create_seq_node:
>  		if (rc == ZOK) {
>  			sd_debug("call zoo_exists success %s", lowest_seq_path);
>  			/* Use wait_timeout to avoid missing wakeup signal */
> -			sd_cond_wait_timeout(&cluster_lock->wait_wakeup,
> -					     &cluster_lock->wait_mutex,
> -					     WAIT_TIME * 2);
> +			sem_wait(&cluster_lock->wait_wakeup);
>  		} else {
>  			sd_debug("failed to call zoo_exists %s", zerror(rc));
>  			if (rc != ZNONODE)
> -- 
> 1.7.12.4
> 
> -- 
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Applied thanks

Yuan