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Bug#58136: Crash in vio_close at concurrent disconnect and KILL

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The problem is a race between a session closing its vio
(i.e. after a COM_QUIT) at the same time it is being killed by
another thread. This could trigger a assertion in vio_close()
as the two threads could end up closing the same vio, at the
same time. This could happen due to the implementation of
SIGNAL_WITH_VIO_CLOSE, which closes the vio of the thread
being killed.

The solution is to serialize the close of the Vio under
LOCK_thd_data, which protects THD data.

No regression test is added as this is essentially a debug
issue and the test case would be quite convoluted as we would
need to synchronize a session that is being killed -- which
is a bit difficult since debug sync points code does not
synchronize killed sessions.
This commit is contained in:
Davi Arnaut 2010-12-15 20:59:21 -02:00
parent eb5a21dd90
commit 487f9bb219
6 changed files with 59 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
sql/mysqld.cc
View File

@ -1134,7 +1134,7 @@ static void close_connections(void)
tmp->thread_id,
(tmp->main_security_ctx.user ?
tmp->main_security_ctx.user : ""));
close_connection(tmp,0,0);
close_connection(tmp);
}
#endif
DBUG_PRINT("quit",("Unlocking LOCK_thread_count"));
@ -1960,39 +1960,28 @@ static void network_init(void)
/**
Close a connection.
@param thd Thread handle
@param errcode Error code to print to console
@param lock 1 if we have have to lock LOCK_thread_count
@param thd Thread handle.
@param sql_errno The error code to send before disconnect.
@note
For the connection that is doing shutdown, this is called twice
*/
void close_connection(THD *thd, uint errcode, bool lock)
void close_connection(THD *thd, uint sql_errno)
{
st_vio *vio;
DBUG_ENTER("close_connection");
DBUG_PRINT("enter",("fd: %s error: '%s'",
thd->net.vio ? vio_description(thd->net.vio) :
"(not connected)",
errcode ? ER_DEFAULT(errcode) : ""));
if (lock)
mysql_mutex_lock(&LOCK_thread_count);
thd->killed= THD::KILL_CONNECTION;
if ((vio= thd->net.vio) != 0)
{
if (errcode)
net_send_error(thd, errcode,
ER_DEFAULT(errcode), NULL); /* purecov: inspected */
vio_close(vio); /* vio is freed in delete thd */
}
if (lock)
mysql_mutex_unlock(&LOCK_thread_count);
MYSQL_CONNECTION_DONE((int) errcode, thd->thread_id);
if (sql_errno)
net_send_error(thd, sql_errno, ER_DEFAULT(sql_errno), NULL);
thd->disconnect();
MYSQL_CONNECTION_DONE((int) sql_errno, thd->thread_id);
if (MYSQL_CONNECTION_DONE_ENABLED())
{
sleep(0); /* Workaround to avoid tailcall optimisation */
}
MYSQL_AUDIT_NOTIFY_CONNECTION_DISCONNECT(thd, errcode);
MYSQL_AUDIT_NOTIFY_CONNECTION_DISCONNECT(thd, sql_errno);
DBUG_VOID_RETURN;
}
#endif /* EMBEDDED_LIBRARY */
@ -4951,8 +4940,8 @@ void create_thread_to_handle_connection(THD *thd)
my_snprintf(error_message_buff, sizeof(error_message_buff),
ER_THD(thd, ER_CANT_CREATE_THREAD), error);
net_send_error(thd, ER_CANT_CREATE_THREAD, error_message_buff, NULL);
close_connection(thd);
mysql_mutex_lock(&LOCK_thread_count);
close_connection(thd,0,0);
delete thd;
mysql_mutex_unlock(&LOCK_thread_count);
return;
@ -4993,7 +4982,7 @@ static void create_new_thread(THD *thd)
mysql_mutex_unlock(&LOCK_connection_count);
DBUG_PRINT("error",("Too many connections"));
close_connection(thd, ER_CON_COUNT_ERROR, 1);
close_connection(thd, ER_CON_COUNT_ERROR);
delete thd;
DBUG_VOID_RETURN;
}
@ -5374,7 +5363,7 @@ pthread_handler_t handle_connections_namedpipes(void *arg)
if (!(thd->net.vio= vio_new_win32pipe(hConnectedPipe)) ||
my_net_init(&thd->net, thd->net.vio))
{
close_connection(thd, ER_OUT_OF_RESOURCES, 1);
close_connection(thd, ER_OUT_OF_RESOURCES);
delete thd;
continue;
}
@ -5569,7 +5558,7 @@ pthread_handler_t handle_connections_shared_memory(void *arg)
event_conn_closed)) ||
my_net_init(&thd->net, thd->net.vio))
{
close_connection(thd, ER_OUT_OF_RESOURCES, 1);
close_connection(thd, ER_OUT_OF_RESOURCES);
errmsg= 0;
goto errorconn;
}

2
sql/mysqld.h
View File

@ -64,7 +64,7 @@ typedef Bitmap<((MAX_INDEXES+7)/8*8)> key_map; /* Used for finding keys */
some places */
/* Function prototypes */
void kill_mysql(void);
void close_connection(THD *thd, uint errcode, bool lock);
void close_connection(THD *thd, uint sql_errno= 0);
void handle_connection_in_main_thread(THD *thd);
void create_thread_to_handle_connection(THD *thd);
void unlink_thd(THD *thd);

34
sql/sql_class.cc
View File

@ -1283,6 +1283,40 @@ void THD::awake(THD::killed_state state_to_set)
DBUG_VOID_RETURN;
}
/**
Close the Vio associated this session.
@remark LOCK_thd_data is taken due to the fact that
the Vio might be disassociated concurrently.
*/
void THD::disconnect()
{
Vio *vio= NULL;
mysql_mutex_lock(&LOCK_thd_data);
killed= THD::KILL_CONNECTION;
#ifdef SIGNAL_WITH_VIO_CLOSE
/*
Since a active vio might might have not been set yet, in
any case save a reference to avoid closing a inexistent
one or closing the vio twice if there is a active one.
*/
vio= active_vio;
close_active_vio();
#endif
/* Disconnect even if a active vio is not associated. */
if (net.vio != vio)
vio_close(net.vio);
mysql_mutex_unlock(&LOCK_thd_data);
}
/*
Remember the location of thread info, the structure needed for
sql_alloc() and the structure for the net buffer

3
sql/sql_class.h
View File

@ -2209,6 +2209,9 @@ public:
#endif
void awake(THD::killed_state state_to_set);
/** Disconnect the associated communication endpoint. */
void disconnect();
#ifndef MYSQL_CLIENT
enum enum_binlog_query_type {
/* The query can be logged in row format or in statement format. */

6
sql/sql_connect.cc
View File

@ -518,7 +518,7 @@ bool setup_connection_thread_globals(THD *thd)
{
if (thd->store_globals())
{
close_connection(thd, ER_OUT_OF_RESOURCES, 1);
close_connection(thd, ER_OUT_OF_RESOURCES);
statistic_increment(aborted_connects,&LOCK_status);
MYSQL_CALLBACK(thread_scheduler, end_thread, (thd, 0));
return 1; // Error
@ -693,7 +693,7 @@ void do_handle_one_connection(THD *thd_arg)
if (MYSQL_CALLBACK_ELSE(thread_scheduler, init_new_connection_thread, (), 0))
{
close_connection(thd, ER_OUT_OF_RESOURCES, 1);
close_connection(thd, ER_OUT_OF_RESOURCES);
statistic_increment(aborted_connects,&LOCK_status);
MYSQL_CALLBACK(thread_scheduler, end_thread, (thd, 0));
return;
@ -751,7 +751,7 @@ void do_handle_one_connection(THD *thd_arg)
end_connection(thd);
end_thread:
close_connection(thd, 0, 1);
close_connection(thd);
if (MYSQL_CALLBACK_ELSE(thread_scheduler, end_thread, (thd, 1), 0))
return; // Probably no-threads

2
sql/sql_parse.cc
View File

@ -600,7 +600,7 @@ void do_handle_bootstrap(THD *thd)
if (my_thread_init() || thd->store_globals())
{
#ifndef EMBEDDED_LIBRARY
close_connection(thd, ER_OUT_OF_RESOURCES, 1);
close_connection(thd, ER_OUT_OF_RESOURCES);
#endif
thd->fatal_error();
goto end;