[sr-dev] git:3.1: tm: recursive hash locks

[Daniel-Constantin Mierla]

Module: sip-router
Branch: 3.1
Commit: 06b74b600e6644f4bf289d256538d463f6734717
URL:    http://git.sip-router.org/cgi-bin/gitweb.cgi/sip-router/?a=commit;h=06b74b600e6644f4bf289d256538d463f6734717

Author: Andrei Pelinescu-Onciul <andrei at iptel.org>
Committer: Daniel-Constantin Mierla <miconda at gmail.com>
Date:   Fri Apr 29 19:40:36 2011 +0200

tm: recursive hash locks

The hash locks are now recursive/re-entrant.
This removes some of the TMCB_REQUEST_IN and TMCB_LOCAL_REQUEST_IN
callback restrictions (like do not create new transactions,
do not  call t_lookup_*()) solving problems like the one
described in
http://lists.sip-router.org/pipermail/sr-users/2011-April/068331.html
(cherry picked from commit 1699b6a4c479031c116fb081a805635a4d088bcb)

---

 modules/tm/h_table.c |   20 ++++++++++++++++++--
 modules/tm/h_table.h |    2 ++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/modules/tm/h_table.c b/modules/tm/h_table.c
index 33e72d7..c82f0b9 100644
--- a/modules/tm/h_table.c
+++ b/modules/tm/h_table.c
@@ -97,13 +97,29 @@ enum kill_reason get_kr() {
 
 void lock_hash(int i) 
 {
-	lock(&_tm_table->entries[i].mutex);
+
+	int mypid;
+
+	mypid = my_pid();
+	if (likely(atomic_get(&_tm_table->entries[i].locker_pid) != mypid)) {
+		lock(&_tm_table->entries[i].mutex);
+		atomic_set(&_tm_table->entries[i].locker_pid, mypid);
+	} else {
+		/* locked within the same process that called us*/
+		_tm_table->entries[i].rec_lock_level++;
+	}
 }
 
 
 void unlock_hash(int i) 
 {
-	unlock(&_tm_table->entries[i].mutex);
+	if (likely(_tm_table->entries[i].rec_lock_level == 0)) {
+		atomic_set(&_tm_table->entries[i].locker_pid, 0);
+		unlock(&_tm_table->entries[i].mutex);
+	} else  {
+		/* recursive locked => decrease rec. lock count */
+		_tm_table->entries[i].rec_lock_level--;
+	}
 }
 
 
diff --git a/modules/tm/h_table.h b/modules/tm/h_table.h
index 784606e..ea2fa14 100644
--- a/modules/tm/h_table.h
+++ b/modules/tm/h_table.h
@@ -429,6 +429,8 @@ typedef struct entry
 	struct cell*    prev_c;
 	/* sync mutex */
 	ser_lock_t      mutex;
+	atomic_t locker_pid; /* pid of the process that holds the lock */
+	int rec_lock_level; /* recursive lock count */
 	/* currently highest sequence number in a synonym list */
 	unsigned int    next_label;
 #ifdef TM_HASH_STATS