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Some general tidyup plus addition of code to block zombie processing

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if epoll_wait returned multiple descriptors
This commit is contained in:
Mark Riddoch
2014-09-19 10:50:54 +01:00
parent a5975d8cff
commit 2402d55de6
4 changed files with 112 additions and 69 deletions
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153
server/core/dcb.c
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@ -403,13 +403,16 @@ DCB_CALLBACK *cb;
* operation of clearing this bit means that no bits are set in
* the memdata.bitmask then the DCB is no longer able to be
* referenced and it can be finally removed.
* Thread won't clear its bit from bitmask of the DCB it is still using.
*
* The excluded DCB allows a thread to exclude a DCB from zombie processing.
* It is used when a thread calls dcb_process_zombies when there is
* a DCB that the caller knows it will continue processing with.
*
* @param threadid The thread ID of the caller
* @param dcb_in_use The DCB the thread currently uses, NULL or valid DCB.
* @param excluded The DCB the thread currently uses, NULL or valid DCB.
*/
DCB *
dcb_process_zombies(int threadid, DCB *dcb_in_use)
dcb_process_zombies(int threadid, DCB *excluded)
{
DCB *ptr, *lptr;
DCB* dcb_list = NULL;
@ -426,78 +429,100 @@ bool succp = false;
if (!zombies)
return NULL;
/*
* Process the zombie queue and create a list of DCB's that can be
* finally freed. This processing is down under a spinlock that
* will prevent new entries being added to the zombie queue. Therefore
* we do not want to do any expensive operations under this spinlock
* as it will block other threads. The expensive operations will be
* performed on the victim queue within holding the zombie queue
* spinlock.
*/
spinlock_acquire(&zombiespin);
ptr = zombies;
lptr = NULL;
while (ptr)
{
CHK_DCB(ptr);
/** Don't clear the bit from DCB the user currently uses */
if (dcb_in_use == NULL || ptr != dcb_in_use)
{
bitmask_clear(&ptr->memdata.bitmask, threadid);
}
if (ptr == dcb_in_use)
ss_dassert(!bitmask_isallclear(&ptr->memdata.bitmask));
if (bitmask_isallclear(&ptr->memdata.bitmask))
{
/**
* Remove the DCB from the zombie queue
* and call the final free routine for the
* DCB
*
* ptr is the DCB we are processing
* lptr is the previous DCB on the zombie queue
* or NULL if the DCB is at the head of the queue
* tptr is the DCB after the one we are processing
* on the zombie queue
*/
DCB *tptr = ptr->memdata.next;
if (lptr == NULL)
zombies = tptr;
else
lptr->memdata.next = tptr;
LOGIF(LD, (skygw_log_write_flush(
LOGFILE_DEBUG,
"%lu [dcb_process_zombies] Remove dcb %p fd %d "
"in state %s from zombies list.",
pthread_self(),
ptr,
ptr->fd,
STRDCBSTATE(ptr->state))));
ss_info_dassert(ptr->state == DCB_STATE_ZOMBIE,
"dcb not in DCB_STATE_ZOMBIE state.");
/*<
* Move dcb to linked list of victim dcbs.
*/
if (dcb_list == NULL) {
dcb_list = ptr;
dcb = dcb_list;
} else {
dcb->memdata.next = ptr;
dcb = dcb->memdata.next;
}
dcb->memdata.next = NULL;
ptr = tptr;
}
else
/*
* Skip processing of the excluded DCB
*/
if (ptr == excluded)
{
lptr = ptr;
ptr = ptr->memdata.next;
}
else
{
bitmask_clear(&ptr->memdata.bitmask, threadid);
if (bitmask_isallclear(&ptr->memdata.bitmask))
{
/**
* Remove the DCB from the zombie queue
* and call the final free routine for the
* DCB
*
* ptr is the DCB we are processing
* lptr is the previous DCB on the zombie queue
* or NULL if the DCB is at the head of the
* queue tptr is the DCB after the one we are
* processing on the zombie queue
*/
DCB *tptr = ptr->memdata.next;
if (lptr == NULL)
zombies = tptr;
else
lptr->memdata.next = tptr;
LOGIF(LD, (skygw_log_write_flush(
LOGFILE_DEBUG,
"%lu [dcb_process_zombies] Remove dcb "
"%p fd %d " "in state %s from the "
"list of zombies.",
pthread_self(),
ptr,
ptr->fd,
STRDCBSTATE(ptr->state))));
ss_info_dassert(ptr->state == DCB_STATE_ZOMBIE,
"dcb not in DCB_STATE_ZOMBIE state.");
/*<
* Move dcb to linked list of victim dcbs.
*/
if (dcb_list == NULL) {
dcb_list = ptr;
dcb = dcb_list;
} else {
dcb->memdata.next = ptr;
dcb = dcb->memdata.next;
}
dcb->memdata.next = NULL;
ptr = tptr;
}
else
{
lptr = ptr;
ptr = ptr->memdata.next;
}
}
}
spinlock_release(&zombiespin);
/*
* Process the victim queue. These are DCBs that are not in
* use by any thread.
* The corresponding file descriptor is closed, the DCB marked
* as disconnected and the DCB itself is fianlly freed.
*/
dcb = dcb_list;
/** Close, and set DISCONNECTED victims */
while (dcb != NULL) {
DCB* dcb_next = NULL;
int rc = 0;
/*<
* Close file descriptor and move to clean-up phase.
*/
ss_dassert(dcb_in_use != dcb);
ss_dassert(excluded != dcb);
rc = close(dcb->fd);
if (rc < 0) {
@ -1119,8 +1144,8 @@ int above_water;
/**
* Removes dcb from poll set, and adds it to zombies list. As a consequense,
* dcb first moves to DCB_STATE_NOPOLLING, and then to DCB_STATE_ZOMBIE state.
* At the end of the function state may not be DCB_STATE_ZOMBIE because once dcb_initlock
* is released parallel threads may change the state.
* At the end of the function state may not be DCB_STATE_ZOMBIE because once
* dcb_initlock is released parallel threads may change the state.
*
* Parameters:
* @param dcb The DCB to close
@ -1943,9 +1968,11 @@ int rval = 0;
* to return immediately and and process other events.
*
* @param dcb The DCB that has data available
* @param thread_id The ID of the calling thread
* @param nozombies If non-zero then do not do zombie processing
*/
void
dcb_pollin(DCB *dcb, int thread_id)
dcb_pollin(DCB *dcb, int thread_id, int nozombies)
{
spinlock_acquire(&dcb->pollinlock);
@ -1956,7 +1983,8 @@ dcb_pollin(DCB *dcb, int thread_id)
if (dcb->readcheck)
{
dcb->stats.n_readrechecks++;
dcb_process_zombies(thread_id, dcb);
if (!nozombies)
dcb_process_zombies(thread_id, dcb);
}
dcb->readcheck = 0;
spinlock_release(&dcb->pollinlock);
@ -1987,9 +2015,11 @@ dcb_pollin(DCB *dcb, int thread_id)
* to return immediately and and process other events.
*
* @param dcb The DCB thats available for writes
* @param thread_id The ID of the calling thread
* @param nozombies If non-zero then do not do zombie processing
*/
void
dcb_pollout(DCB *dcb, int thread_id)
dcb_pollout(DCB *dcb, int thread_id, int nozombies)
{
spinlock_acquire(&dcb->polloutlock);
@ -1999,7 +2029,8 @@ dcb_pollout(DCB *dcb, int thread_id)
do {
if (dcb->writecheck)
{
dcb_process_zombies(thread_id, dcb);
if (!nozombies)
dcb_process_zombies(thread_id, dcb);
dcb->stats.n_writerechecks++;
}
dcb->writecheck = 0;