[stgt] [PATCH 1/3] Change lock that protects tgt_events_list to rwlock

[Chandra Seetharaman]

Convert the lock tgt_events_lock to a read write lock tgt_events_rwlock.
This will help with performance as there are more walk-thru the list
than the add/delete operations.

Signed-off-by: Chandra Seetharaman <sekharan at us.ibm.com>
---
 usr/tgtd.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

Index: tgt-thread/usr/tgtd.c
===================================================================
--- tgt-thread.orig/usr/tgtd.c
+++ tgt-thread/usr/tgtd.c
@@ -167,14 +167,14 @@ int do_tgt_event_add(int efd, struct lis
 	return err;
 }
 
-static pthread_mutex_t tgt_events_lock;
+static pthread_rwlock_t tgt_events_rwlock;
 int tgt_event_add(int fd, int events, event_handler_t handler, void *data)
 {
 	int ret;
-	pthread_mutex_lock(&tgt_events_lock);
+	pthread_rwlock_wrlock(&tgt_events_rwlock);
 	ret = do_tgt_event_add(ep_fd, &tgt_events_list, fd, events, handler,
 				data);
-	pthread_mutex_unlock(&tgt_events_lock);
+	pthread_rwlock_unlock(&tgt_events_rwlock);
 	return ret;
 }
 
@@ -210,9 +210,9 @@ void do_tgt_event_del(int efd, struct li
 
 void tgt_event_del(int fd)
 {
-	pthread_mutex_lock(&tgt_events_lock);
+	pthread_rwlock_wrlock(&tgt_events_rwlock);
 	do_tgt_event_del(ep_fd, &tgt_events_list, fd);
-	pthread_mutex_unlock(&tgt_events_lock);
+	pthread_rwlock_unlock(&tgt_events_rwlock);
 }
 
 int do_tgt_event_modify(int efd, struct list_head *list, int fd, int events)
@@ -236,9 +236,9 @@ int do_tgt_event_modify(int efd, struct 
 int tgt_event_modify(int fd, int events)
 {
 	int ret;
-	pthread_mutex_lock(&tgt_events_lock);
+	pthread_rwlock_rdlock(&tgt_events_rwlock);
 	ret = do_tgt_event_modify(ep_fd, &tgt_events_list, fd, events);
-	pthread_mutex_unlock(&tgt_events_lock);
+	pthread_rwlock_unlock(&tgt_events_rwlock);
 	return ret;
 }
 
@@ -469,7 +469,7 @@ int main(int argc, char **argv)
 	sigaction(SIGINT, &sa_new, &sa_old);
 	sigaction(SIGPIPE, &sa_new, &sa_old);
 	sigaction(SIGTERM, &sa_new, &sa_old);
-	pthread_mutex_init(&tgt_events_lock, NULL);
+	pthread_rwlock_init(&tgt_events_rwlock, NULL);
 
 	pagesize = sysconf(_SC_PAGESIZE);
 	for (pageshift = 0;; pageshift++)
--
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