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Bug#33899: Deadlock in mysql_real_query with shared memory connections

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The problem is that the read and write methods of the shared
memory transport (protocol) didn't react to asynchornous close
events, which could lead to a lock up as the client would wait
(until time out) for a server response that will never come.

The solution is to also wait for close events while waiting
for I/O from or to the server.

Bug report and patch submitted by: Armin Schöffmann
This commit is contained in:
Davi Arnaut 2009-03-26 20:25:10 -03:00
commit 7c2612135f
3 changed files with 41 additions and 7 deletions
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22
vio/viosocket.c
View file

@ -480,19 +480,22 @@ size_t vio_read_shared_memory(Vio * vio, uchar* buf, size_t size)
size_t length;
size_t remain_local;
char *current_postion;
HANDLE events[2];
DBUG_ENTER("vio_read_shared_memory");
DBUG_PRINT("enter", ("sd: %d buf: 0x%lx size: %d", vio->sd, (long) buf,
size));
remain_local = size;
current_postion=buf;
events[0]= vio->event_server_wrote;
events[1]= vio->event_conn_closed;
do
{
if (vio->shared_memory_remain == 0)
{
HANDLE events[2];
events[0]= vio->event_server_wrote;
events[1]= vio->event_conn_closed;
/*
WaitForMultipleObjects can return next values:
WAIT_OBJECT_0+0 - event from vio->event_server_wrote
@ -500,7 +503,7 @@ size_t vio_read_shared_memory(Vio * vio, uchar* buf, size_t size)
anything
WAIT_ABANDONED_0 and WAIT_TIMEOUT - fail. We can't read anything
*/
if (WaitForMultipleObjects(2, (HANDLE*)&events,FALSE,
if (WaitForMultipleObjects(array_elements(events), events, FALSE,
vio->net->read_timeout*1000) != WAIT_OBJECT_0)
{
DBUG_RETURN(-1);
@ -543,17 +546,22 @@ size_t vio_write_shared_memory(Vio * vio, const uchar* buf, size_t size)
size_t length, remain, sz;
HANDLE pos;
const uchar *current_postion;
HANDLE events[2];
DBUG_ENTER("vio_write_shared_memory");
DBUG_PRINT("enter", ("sd: %d buf: 0x%lx size: %d", vio->sd, (long) buf,
size));
remain = size;
current_postion = buf;
events[0]= vio->event_server_read;
events[1]= vio->event_conn_closed;
while (remain != 0)
{
if (WaitForSingleObject(vio->event_server_read,
vio->net->write_timeout*1000) !=
WAIT_OBJECT_0)
if (WaitForMultipleObjects(array_elements(events), events, FALSE,
vio->net->write_timeout*1000) != WAIT_OBJECT_0)
{
DBUG_RETURN((size_t) -1);
}