hcq/MaxScale
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Remove spinlocks from readwritesplit

Browse Source 
Spinlocks are no longer necessary as the threading model only allows a
specific thread to access the router session.
This commit is contained in:
Markus Mäkelä
2017-02-27 09:54:57 +02:00
parent d834c1bbdc
commit 677e8aaabf
6 changed files with 18 additions and 197 deletions
Download Patch File Download Diff File Expand all files Collapse all files

132
server/modules/routing/readwritesplit/readwritesplit.c
View File

@ -250,7 +250,6 @@ static MXS_ROUTER *createInstance(SERVICE *service, char **options)
return NULL;
}
router->service = service;
spinlock_init(&router->lock);
/*
* Until we know otherwise assume we have some available slaves.
@ -331,7 +330,6 @@ static MXS_ROUTER_SESSION *newSession(MXS_ROUTER *router_inst, MXS_SESSION *sess
client_rses->client_dcb = session->client_dcb;
client_rses->have_tmp_tables = false;
client_rses->forced_node = NULL;
spinlock_init(&client_rses->rses_lock);
memcpy(&client_rses->rses_config, &router->rwsplit_config, sizeof(client_rses->rses_config));
int router_nservers = router->service->n_dbref;
@ -409,7 +407,7 @@ static void closeSession(MXS_ROUTER *instance, MXS_ROUTER_SESSION *router_sessio
ROUTER_CLIENT_SES *router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
CHK_CLIENT_RSES(router_cli_ses);
if (!router_cli_ses->rses_closed && rses_begin_locked_router_action(router_cli_ses))
if (!router_cli_ses->rses_closed)
{
/**
* Mark router session as closed. @c rses_closed is checked at the start
@ -465,8 +463,6 @@ static void closeSession(MXS_ROUTER *instance, MXS_ROUTER_SESSION *router_sessio
}
}
}
rses_end_locked_router_action(router_cli_ses);
}
}
@ -670,31 +666,22 @@ static void clientReply(MXS_ROUTER *instance,
GWBUF *writebuf,
DCB *backend_dcb)
{
DCB *client_dcb;
ROUTER_INSTANCE *router_inst;
ROUTER_CLIENT_SES *router_cli_ses;
sescmd_cursor_t *scur = NULL;
backend_ref_t *bref;
ROUTER_CLIENT_SES *router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
ROUTER_INSTANCE *router_inst = (ROUTER_INSTANCE *)instance;
DCB *client_dcb = backend_dcb->session->client_dcb;
router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
router_inst = (ROUTER_INSTANCE *)instance;
CHK_CLIENT_RSES(router_cli_ses);
/**
* Lock router client session for secure read of router session members.
* Note that this could be done without lock by using version #
*/
if (!rses_begin_locked_router_action(router_cli_ses))
if (router_cli_ses->rses_closed)
{
gwbuf_free(writebuf);
goto lock_failed;
return;
}
/** Holding lock ensures that router session remains open */
ss_dassert(backend_dcb->session != NULL);
client_dcb = backend_dcb->session->client_dcb;
/** Unlock */
rses_end_locked_router_action(router_cli_ses);
/**
* 1. Check if backend received reply to sescmd.
* 2. Check sescmd's state whether OK_PACKET has been
@ -704,32 +691,10 @@ static void clientReply(MXS_ROUTER *instance,
* 3. If reply for this sescmd is sent, lock property cursor
* and
*/
if (client_dcb == NULL)
{
gwbuf_free(writebuf);
/** Log that client was closed before reply */
goto lock_failed;
}
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
/** Log to debug that router was closed */
goto lock_failed;
}
bref = get_bref_from_dcb(router_cli_ses, backend_dcb);
#if !defined(FOR_BUG548_FIX_ONLY)
/** This makes the issue becoming visible in poll.c */
if (bref == NULL)
{
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
goto lock_failed;
}
#endif
backend_ref_t *bref = get_bref_from_dcb(router_cli_ses, backend_dcb);
CHK_BACKEND_REF(bref);
scur = &bref->bref_sescmd_cur;
sescmd_cursor_t *scur = &bref->bref_sescmd_cur;
/** Statement was successfully executed, free the stored statement */
session_clear_stmt(backend_dcb->session);
@ -790,15 +755,7 @@ static void clientReply(MXS_ROUTER *instance,
/** Write reply to client DCB */
MXS_SESSION_ROUTE_REPLY(backend_dcb->session, writebuf);
}
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
/** Log to debug that router was closed */
goto lock_failed;
}
/** There is one pending session command to be executed. */
if (sescmd_cursor_is_active(scur))
{
@ -849,11 +806,6 @@ static void clientReply(MXS_ROUTER *instance,
gwbuf_free(bref->bref_pending_cmd);
bref->bref_pending_cmd = NULL;
}
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
lock_failed:
return;
}
@ -878,64 +830,6 @@ static uint64_t getCapabilities(MXS_ROUTER* instance)
* functions are not intended for use outside the read write split router.
*/
/**
* @brief Acquires lock to router client session if it is not closed.
*
* Parameters:
* @param rses - in, use
*
*
* @return true if router session was not closed. If return value is true
* it means that router is locked, and must be unlocked later. False, if
* router was closed before lock was acquired.
*
*/
bool rses_begin_locked_router_action(ROUTER_CLIENT_SES *rses)
{
bool succp = false;
if (rses == NULL)
{
return false;
}
CHK_CLIENT_RSES(rses);
if (rses->rses_closed)
{
goto return_succp;
}
spinlock_acquire(&rses->rses_lock);
if (rses->rses_closed)
{
spinlock_release(&rses->rses_lock);
goto return_succp;
}
succp = true;
return_succp:
return succp;
}
/** to be inline'd */
/**
* @brief Releases router client session lock.
*
* Parameters:
* @param rses - <usage>
* <description>
*
* @return void
*
*/
void rses_end_locked_router_action(ROUTER_CLIENT_SES *rses)
{
CHK_CLIENT_RSES(rses);
spinlock_release(&rses->rses_lock);
}
/*
* @brief Clear one or more bits in the backend reference state
*
@ -1158,6 +1052,10 @@ backend_ref_t *get_bref_from_dcb(ROUTER_CLIENT_SES *rses, DCB *dcb)
{
bref = NULL;
}
/** We should always have a valid backend reference */
ss_dassert(bref);
return bref;
}
@ -1366,7 +1264,7 @@ static void handleError(MXS_ROUTER *instance,
CHK_DCB(problem_dcb);
if (!rses_begin_locked_router_action(rses))
if (rses->rses_closed)
{
/** Session is already closed */
problem_dcb->dcb_errhandle_called = true;
@ -1383,7 +1281,6 @@ static void handleError(MXS_ROUTER *instance,
* be safe with the code as it stands on 9 Sept 2015 - MNB
*/
*succp = true;
rses_end_locked_router_action(rses);
return;
}
else
@ -1521,8 +1418,6 @@ static void handleError(MXS_ROUTER *instance,
break;
}
}
rses_end_locked_router_action(rses);
}
/**
@ -1642,7 +1537,6 @@ static bool handle_error_new_connection(ROUTER_INSTANCE *inst,
bool succp;
myrses = *rses;
ss_dassert(SPINLOCK_IS_LOCKED(&myrses->rses_lock));
ses = backend_dcb->session;
CHK_SESSION(ses);