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

Simplify adding and removing DCBs from polling, improve error handling. Remove dcb_set_state functions as not adding value.

Browse Source
This commit is contained in:
counterpoint
2015-07-06 14:50:01 +01:00
parent a72f462e2d
commit 18a95eeb71
3 changed files with 105 additions and 261 deletions
Download Patch File Download Diff File Expand all files Collapse all files

164
server/core/poll.c
View File

@ -189,7 +189,7 @@ static void poll_loadav(void *);
/**
* Function to analyse error return from epoll_ctl
*/
static int poll_resolve_error(int, bool);
static int poll_resolve_error(DCB *, int, bool);
/**
* Initialise the polling system we are using for the gateway.
@ -252,7 +252,7 @@ int
poll_add_dcb(DCB *dcb)
{
int rc = -1;
dcb_state_t old_state = DCB_STATE_UNDEFINED;
dcb_state_t old_state = dcb->state;
dcb_state_t new_state;
struct epoll_event ev;
@ -268,47 +268,71 @@ poll_add_dcb(DCB *dcb)
/*<
* Choose new state according to the role of dcb.
*/
spinlock_acquire(&dcb->dcb_initlock);
if (dcb->dcb_role == DCB_ROLE_REQUEST_HANDLER) {
new_state = DCB_STATE_POLLING;
} else {
ss_dassert(dcb->dcb_role == DCB_ROLE_SERVICE_LISTENER);
new_state = DCB_STATE_LISTENING;
}
/*
* Check DCB current state seems sensible
*/
if (DCB_STATE_DISCONNECTED == dcb->state
|| DCB_STATE_ZOMBIE == dcb->state
|| DCB_STATE_UNDEFINED == dcb->state)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"%lu [poll_add_dcb] Error : existing state of dcb %p "
"is %s, but this should be impossible, crashing.",
pthread_self(),
dcb,
STRDCBSTATE(dcb->state))));
assert(false);
}
if (DCB_STATE_POLLING == dcb->state
|| DCB_STATE_LISTENING == dcb->state)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"%lu [poll_add_dcb] Error : existing state of dcb %p "
"is %s, but this is probably an error, not crashing.",
pthread_self(),
dcb,
STRDCBSTATE(dcb->state))));
}
/*<
* If dcb is in unexpected state, state change fails indicating that dcb
* is not polling anymore.
*/
if (dcb_set_state(dcb, new_state, &old_state)) {
rc = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, dcb->fd, &ev);
if (rc) rc = poll_resolve_error(errno, true);
if (0 == rc)
{
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_add_dcb] Added dcb %p in state %s to "
"poll set.",
pthread_self(),
dcb,
STRDCBSTATE(dcb->state))));
}
else dcb_revert_state(dcb, new_state, old_state);
} else {
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to set new state for dcb %p "
"in state %s. Adding to poll set failed.",
dcb,
STRDCBSTATE(dcb->state))));
dcb->state = new_state;
spinlock_release(&dcb->dcb_initlock);
/*
* The only possible failure that will not cause a crash is
* running out of system resources.
*/
rc = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, dcb->fd, &ev);
if (rc)
{
rc = poll_resolve_error(dcb, errno, true);
}
if (0 == rc)
{
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_add_dcb] Added dcb %p in state %s to poll set.",
pthread_self(),
dcb,
STRDCBSTATE(dcb->state))));
}
else dcb->state = old_state;
return rc;
}
/**
* Remove a descriptor from the set of descriptors within the
* polling environment.
* The state change command may fail because concurrent threads may call
* dcb_set_state simultaneously and the conflict is prevented in dcb_set_state.
*
* @param dcb The descriptor to remove
* @return -1 on error or 0 on success
@ -316,52 +340,53 @@ poll_add_dcb(DCB *dcb)
int
poll_remove_dcb(DCB *dcb)
{
struct epoll_event ev;
int rc = -1;
dcb_state_t old_state = DCB_STATE_UNDEFINED;
dcb_state_t new_state = DCB_STATE_NOPOLLING;
CHK_DCB(dcb);
spinlock_acquire(&dcb->dcb_initlock);
/*< It is possible that dcb has already been removed from the set */
if (dcb->state != DCB_STATE_POLLING &&
dcb->state != DCB_STATE_LISTENING)
{
if (dcb->state == DCB_STATE_NOPOLLING ||
dcb->state == DCB_STATE_ZOMBIE)
{
rc = 0;
}
goto return_rc;
if (dcb->state == DCB_STATE_NOPOLLING ||
dcb->state == DCB_STATE_ZOMBIE)
{
spinlock_release(&dcb->dcb_initlock);
return 0;
}
if (DCB_STATE_POLLING != dcb->state
&& DCB_STATE_LISTENING != dcb->state)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"%lu [poll_remove_dcb] Error : existing state of dcb %p "
"is %s, but this is probably an error, not crashing.",
pthread_self(),
dcb,
STRDCBSTATE(dcb->state))));
}
/*<
* Set state to NOPOLLING and remove dcb from poll set.
*/
if (dcb_set_state(dcb, new_state, &old_state))
{
/**
* Only positive fds can be removed from epoll set.
*/
if (dcb->fd > 0)
{
rc = epoll_ctl(epoll_fd, EPOLL_CTL_DEL, dcb->fd, &ev);
if (rc) rc = poll_resolve_error(errno, false);
}
}
/*<
* This call was redundant, but the end result is correct.
dcb->state = DCB_STATE_NOPOLLING;
/**
* Only positive fds can be removed from epoll set.
* But this test was removed by Martin as it is hard to
* see that there should ever be a situation where
* fd isn't positive and the DCB is also in the poll list.
*/
/* if (dcb->fd > 0) { */
spinlock_release(&dcb->dcb_initlock);
rc = epoll_ctl(epoll_fd, EPOLL_CTL_DEL, dcb->fd, &ev);
/**
* The poll_resolve_error function will always
* return 0 or crash. So if it returns non-zero result,
* things have gone wrong and we crash.
*/
else if (old_state == new_state)
{
rc = 0;
goto return_rc;
}
if (rc) rc = poll_resolve_error(dcb, errno, false);
if (rc) assert(false);
/*< Set bit for each maxscale thread */
bitmask_copy(&dcb->memdata.bitmask, poll_bitmask());
rc = 0;
return_rc:
bitmask_copy(&dcb->memdata.bitmask, poll_bitmask());
return rc;
/* } */
}
/**
@ -377,7 +402,7 @@ return_rc:
* @return -1 on error or 0 for possibly revised return code
*/
static int
poll_resolve_error(int errornum, bool adding)
poll_resolve_error(DCB *dcb, int errornum, bool adding)
{
if (adding)
{
@ -385,7 +410,10 @@ poll_resolve_error(int errornum, bool adding)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : epoll_ctl could not add, already exists.")));
"%lu [poll_resolve_error] Error : epoll_ctl could not add, "
"already exists for DCB %p.",
pthread_self(),
dcb)));
// Assume another thread added and no serious harm done
return 0;
}
@ -393,9 +421,12 @@ poll_resolve_error(int errornum, bool adding)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"The limit imposed by /proc/sys/fs/epoll/max_user_watches was "
"%lu [poll_resolve_error] The limit imposed by "
"/proc/sys/fs/epoll/max_user_watches was "
"encountered while trying to register (EPOLL_CTL_ADD) a new "
"file descriptor on an epoll instance.")));
"file descriptor on an epoll instance for dcb %p.",
pthread_self(),
dcb)));
/* Failure - assume handled by callers */
return -1;
}
@ -407,7 +438,10 @@ poll_resolve_error(int errornum, bool adding)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : epoll_ctl could not remove, not found.")));
"%lu [poll_resolve_error] Error : epoll_ctl could not remove, "
"not found, for dcb %p.",
pthread_self(),
dcb)));
// Assume another thread removed and no serious harm done
return 0;
}