Backport of Bug#10374 to mysql-next-mr

------------------------------------------------------------
revno: 2597.37.3
revision-id: sp1r-davi@mysql.com/endora.local-20080328123626-16430
parent: sp1r-anozdrin/alik@quad.opbmk-20080327125300-11290
committer: davi@mysql.com/endora.local
timestamp: Fri 2008-03-28 09:36:26 -0300
message:
  Bug#10374 GET_LOCK does not let connection to close on the server side if it's aborted

  The problem is that the server doesn't detect aborted connections which
  are waiting on a lock or sleeping (user sleep), wasting system resources
  for a connection that is already dead.

  The solution is to peek at the connection every five seconds to verify if
  the connection is not aborted. A aborted connection is detect by polling
  the connection socket for available data to be read or end of file and in
  case of eof, the wait is aborted and the connection killed.

include/violite.h:
  Export vio_peek_read function.
mysql-test/r/dirty_close.result:
  Add test case result for Bug#10374
mysql-test/t/dirty_close.test:
  Add test case for Bug#10374
sql/item_func.cc:
  While waiting for a condition to be signaled, check if the connection
  is not broken every INTERRUPT_INTERVAL seconds.
sql/sql_class.cc:
  Add function which checks if the client connection was aborted.
sql/sql_class.h:
  Add function prototype.
vio/viosocket.c:
  Add poll and peek functions for Windows and Unix.

1 files changed, 48 insertions, 10 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index f4db3ef03e7..8f2739f8e77 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -3437,6 +3437,48 @@ void debug_sync_point(const char* lock_name, uint lock_timeout)
 
 #endif
 
+
+/**
+  Wait for a given condition to be signaled within the specified timeout.
+
+  @param cond the condition variable to wait on
+  @param lock the associated mutex
+  @param abstime the amount of time in seconds to wait
+
+  @retval return value from pthread_cond_timedwait
+*/
+
+#define INTERRUPT_INTERVAL (5 * ULL(1000000000))
+
+static int interruptible_wait(THD *thd, pthread_cond_t *cond,
+                              pthread_mutex_t *lock, double time)
+{
+  int error;
+  struct timespec abstime;
+  ulonglong slice, timeout= (ulonglong) (time * 1000000000.0);
+
+  do
+  {
+    /* Wait for a fixed interval. */
+    if (timeout > INTERRUPT_INTERVAL)
+      slice= INTERRUPT_INTERVAL;
+    else
+      slice= timeout;
+
+    timeout-= slice;
+    set_timespec_nsec(abstime, slice);
+    error= pthread_cond_timedwait(cond, lock, &abstime);
+    if (error == ETIMEDOUT || error == ETIME)
+    {
+      /* Return error if timed out or connection is broken. */
+      if (!timeout || !thd->vio_is_connected())
+        break;
+    }
+  } while (error && timeout);
+
+  return error;
+}
+
 /**
   Get a user level lock.  If the thread has an old lock this is first released.
 
@@ -3452,8 +3494,7 @@ longlong Item_func_get_lock::val_int()
 {
   DBUG_ASSERT(fixed == 1);
   String *res=args[0]->val_str(&value);
-  longlong timeout=args[1]->val_int();
-  struct timespec abstime;
+  double timeout= args[1]->val_real();
   THD *thd=current_thd;
   User_level_lock *ull;
   int error;
@@ -3517,12 +3558,11 @@ longlong Item_func_get_lock::val_int()
   thd->mysys_var->current_mutex= &LOCK_user_locks;
   thd->mysys_var->current_cond=  &ull->cond;
 
-  set_timespec(abstime,timeout);
   error= 0;
   while (ull->locked && !thd->killed)
   {
     DBUG_PRINT("info", ("waiting on lock"));
-    error= pthread_cond_timedwait(&ull->cond,&LOCK_user_locks,&abstime);
+    error= interruptible_wait(thd, &ull->cond, &LOCK_user_locks, timeout);
     if (error == ETIMEDOUT || error == ETIME)
     {
       DBUG_PRINT("info", ("lock wait timeout"));
@@ -3717,13 +3757,13 @@ void Item_func_benchmark::print(String *str, enum_query_type query_type)
 longlong Item_func_sleep::val_int()
 {
   THD *thd= current_thd;
-  struct timespec abstime;
   pthread_cond_t cond;
+  double timeout;
   int error;
 
   DBUG_ASSERT(fixed == 1);
 
-  double time= args[0]->val_real();
+  timeout= args[0]->val_real();
   /*
     On 64-bit OSX pthread_cond_timedwait() waits forever
     if passed abstime time has already been exceeded by 
@@ -3733,10 +3773,8 @@ longlong Item_func_sleep::val_int()
     We assume that the lines between this test and the call 
     to pthread_cond_timedwait() will be executed in less than 0.00001 sec.
   */
-  if (time < 0.00001)
+  if (timeout < 0.00001)
     return 0;
-    
-  set_timespec_nsec(abstime, (ulonglong)(time * ULL(1000000000)));
 
   pthread_cond_init(&cond, NULL);
   pthread_mutex_lock(&LOCK_user_locks);
@@ -3748,7 +3786,7 @@ longlong Item_func_sleep::val_int()
   error= 0;
   while (!thd->killed)
   {
-    error= pthread_cond_timedwait(&cond, &LOCK_user_locks, &abstime);
+    error= interruptible_wait(thd, &cond, &LOCK_user_locks, timeout);
     if (error == ETIMEDOUT || error == ETIME)
       break;
     error= 0;