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Changes to try to eliminate setting dcb->session to NULL with risk of crashing system.

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This commit is contained in:
counterpoint
2015-08-24 12:12:43 +01:00
parent 5e2e2585ad
commit 37ac158791
7 changed files with 182 additions and 194 deletions
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308
server/core/session.c
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@ -58,6 +58,7 @@ static SESSION *allSessions = NULL;
static int session_setup_filters(SESSION *session);
static void session_simple_free(SESSION *session, DCB *dcb);
/**
* Allocate a new session for a new client of the specified service.
@ -76,8 +77,7 @@ session_alloc(SERVICE *service, DCB *client_dcb)
SESSION *session;
session = (SESSION *)calloc(1, sizeof(SESSION));
ss_info_dassert(session != NULL,
"Allocating memory for session failed.");
ss_info_dassert(session != NULL, "Allocating memory for session failed.");
if (session == NULL)
{
@ -87,43 +87,29 @@ session_alloc(SERVICE *service, DCB *client_dcb)
"session object due error %d, %s.",
errno,
strerror(errno))));
if (client_dcb->data && !DCB_IS_CLONE(client_dcb))
{
void *clientdata = client_dcb->data;
client_dcb->data = NULL;
free(clientdata);
}
goto return_session;
session_simple_free(session, client_dcb);
return NULL;
}
#if defined(SS_DEBUG)
session->ses_chk_top = CHK_NUM_SESSION;
session->ses_chk_tail = CHK_NUM_SESSION;
#endif
if (DCB_IS_CLONE(client_dcb))
{
session->ses_is_child = true;
}
session->ses_is_child = (bool) DCB_IS_CLONE(client_dcb);
spinlock_init(&session->ses_lock);
/*<
* Prevent backend threads from accessing before session is completely
* initialized.
*/
spinlock_acquire(&session->ses_lock);
session->service = service;
session->client = client_dcb;
session->n_filters = 0;
memset(&session->stats, 0, sizeof(SESSION_STATS));
session->stats.connect = time(0);
session->state = SESSION_STATE_ALLOC;
session->client = client_dcb;
session->n_filters = 0;
memset(&session->stats, 0, sizeof(SESSION_STATS));
session->stats.connect = time(0);
session->state = SESSION_STATE_ALLOC;
/*<
* Associate the session to the client DCB and set the reference count on
* the session to indicate that there is a single reference to the
* Associate the session to the client DCB and set the reference count on
* the session to indicate that there is a single reference to the
* session. There is no need to protect this or use atomic add as the
* session has not been made available to the other threads at this
* point.
*/
session->data = client_dcb->data;
client_dcb->session = session;
session->refcount = 1;
/*<
* This indicates that session is ready to be shared with backend
@ -131,139 +117,99 @@ session_alloc(SERVICE *service, DCB *client_dcb)
*/
session->state = SESSION_STATE_READY;
/*< Release session lock */
spinlock_release(&session->ses_lock);
/*
* Only create a router session if we are not the listening
* DCB or an internal DCB. Creating a router session may create a connection to a
* backend server, depending upon the router module implementation
* and should be avoided for the listener session
*
* Router session creation may create other DCBs that link to the
* session, therefore it is important that the session lock is
/*
* Only create a router session if we are not the listening
* DCB or an internal DCB. Creating a router session may create a connection to a
* backend server, depending upon the router module implementation
* and should be avoided for the listener session
*
* Router session creation may create other DCBs that link to the
* session, therefore it is important that the session lock is
* relinquished before the router call.
*/
if (client_dcb->state != DCB_STATE_LISTENING &&
*/
if (client_dcb->state != DCB_STATE_LISTENING &&
client_dcb->dcb_role != DCB_ROLE_INTERNAL)
{
session->router_session =
service->router->newSession(service->router_instance, session);
{
session->router_session = service->router->newSession(service->router_instance, session);
if (session->router_session == NULL)
{
/**
* Inform other threads that session is closing.
*/
session->state = SESSION_STATE_STOPPING;
/*<
* Decrease refcount, set dcb's session pointer NULL
* and set session pointer to NULL.
*/
session->client = NULL;
session_free(session);
client_dcb->session = NULL;
session = NULL;
{
session_simple_free(session, client_dcb);
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Failed to create %s session.",
"%lu [%s] Error : Failed to create %s session because router"
"could not establish a new router session, see earlier error.",
pthread_self(),
__func__,
service->name)));
goto return_session;
return NULL;
}
/*
* Pending filter chain being setup set the head of the chain to
* be the router. As filters are inserted the current head will
* be pushed to the filter and the head updated.
*
* NB This dictates that filters are created starting at the end
* of the chain nearest the router working back to the client
* protocol end of the chain.
*/
session->head.instance = service->router_instance;
session->head.session = session->router_session;
/*
* Pending filter chain being setup set the head of the chain to
* be the router. As filters are inserted the current head will
* be pushed to the filter and the head updated.
*
* NB This dictates that filters are created starting at the end
* of the chain nearest the router working back to the client
* protocol end of the chain.
*/
session->head.instance = service->router_instance;
session->head.session = session->router_session;
session->head.routeQuery = (void *)(service->router->routeQuery);
session->head.routeQuery = (void *)(service->router->routeQuery);
session->tail.instance = session;
session->tail.session = session;
session->tail.clientReply = session_reply;
session->tail.instance = session;
session->tail.session = session;
session->tail.clientReply = session_reply;
if (service->n_filters > 0)
{
if (!session_setup_filters(session))
{
/**
* Inform other threads that session is closing.
*/
session->state = SESSION_STATE_STOPPING;
/*<
* Decrease refcount, set dcb's session pointer NULL
* and set session pointer to NULL.
*/
session->client = NULL;
session_free(session);
client_dcb->session = NULL;
session = NULL;
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Error : Setting up filters failed. "
"Terminating session %s.",
service->name)));
goto return_session;
}
}
}
spinlock_acquire(&session->ses_lock);
if (session->state != SESSION_STATE_READY)
if (service->n_filters > 0)
{
spinlock_release(&session->ses_lock);
session->client = NULL;
session_free(session);
client_dcb->session = NULL;
session = NULL;
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Failed to create %s session.",
service->name)));
spinlock_release(&session_spin);
if (!session_setup_filters(session))
{
session_simple_free(session, client_dcb);
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Error : Setting up filters failed. "
"Terminating session %s.",
service->name)));
return NULL;
}
}
else
{
session->state = SESSION_STATE_ROUTER_READY;
spinlock_release(&session->ses_lock);
spinlock_acquire(&session_spin);
/** Assign a session id and increase */
session->ses_id = ++session_id;
session->next = allSessions;
allSessions = session;
spinlock_release(&session_spin);
}
session->state = SESSION_STATE_ROUTER_READY;
spinlock_acquire(&session_spin);
/** Assign a session id and increase, insert session into list */
session->ses_id = ++session_id;
session->next = allSessions;
allSessions = session;
spinlock_release(&session_spin);
if (session->client->user == NULL)
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started session [%lu] for %s service ",
session->ses_id,
service->name)));
}
else
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started %s client session [%lu] for '%s' from %s",
service->name,
session->ses_id,
session->client->user,
session->client->remote)));
}
atomic_add(&service->stats.n_sessions, 1);
atomic_add(&service->stats.n_current, 1);
CHK_SESSION(session);
}
return_session:
return session;
if (session->client->user == NULL)
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started session [%lu] for %s service ",
session->ses_id,
service->name)));
}
else
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started %s client session [%lu] for '%s' from %s",
service->name,
session->ses_id,
session->client->user,
session->client->remote)));
}
atomic_add(&service->stats.n_sessions, 1);
atomic_add(&service->stats.n_current, 1);
CHK_SESSION(session);
client_dcb->session = session;
return session;
}
/**
@ -360,30 +306,57 @@ int session_unlink_dcb(
return nlink;
}
/**
* Deallocate the specified session, minimal actions during session_alloc
*
* @param session The session to deallocate
*/
static void
session_simple_free(SESSION *session, DCB *dcb)
{
/* Does this possibly need a lock? */
if (dcb->data && !DCB_IS_CLONE(dcb))
{
void * clientdata = dcb->data;
dcb->data = NULL;
free(clientdata);
}
if (session)
{
if (session && session->router_session)
{
session->service->router->freeSession(
session->service->router_instance,
session->router_session);
}
session->state = SESSION_STATE_STOPPING;
}
free(session);
}
/**
* Deallocate the specified session
*
* @param session The session to deallocate
*/
bool session_free(
SESSION *session)
bool
session_free(SESSION *session)
{
bool succp = false;
SESSION *ptr;
int nlink;
int i;
CHK_SESSION(session);
/*<
/*
* Remove one reference. If there are no references left,
* free session.
*/
nlink = session_unlink_dcb(session, NULL);
if (nlink != 0) {
ss_dassert(nlink > 0);
goto return_succp;
if (atomic_add(&session->refcount, -1) - 1)
{
/* Must be one or more references left */
ss_dassert(nlink > 0);
return false;
}
session->state = SESSION_STATE_TO_BE_FREED;
/* First of all remove from the linked list */
spinlock_acquire(&session_spin);
@ -393,13 +366,16 @@ bool session_free(
}
else
{
ptr = allSessions;
while (ptr && ptr->next != session)
SESSION *chksession;
chksession = allSessions;
while (chksession && chksession->next != session)
{
ptr = ptr->next;
chksession = chksession->next;
}
if (ptr)
ptr->next = session->next;
if (chksession)
{
chksession->next = session->next;
}
}
spinlock_release(&session_spin);
atomic_add(&session->service->stats.n_current, -1);
@ -416,6 +392,7 @@ bool session_free(
}
if (session->n_filters)
{
int i;
for (i = 0; i < session->n_filters; i++)
{
if (session->filters[i].filter)
@ -453,10 +430,7 @@ bool session_free(
}
free(session);
}
succp = true;
return_succp :
return succp;
return true;
}
/**