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Real deadlock detection.

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This commit is contained in:
Bruce Momjian
1998-01-27 03:00:43 +00:00
parent 0e91367109
commit 862927f443
4 changed files with 130 additions and 49 deletions
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67
src/backend/storage/lmgr/proc.c
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@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.28 1998/01/25 05:14:09 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.29 1998/01/27 03:00:29 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@@ -46,7 +46,7 @@
* This is so that we can support more backends. (system-wide semaphore
* sets run out pretty fast.) -ay 4/95
*
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.28 1998/01/25 05:14:09 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.29 1998/01/27 03:00:29 momjian Exp $
*/
#include <sys/time.h>
#include <unistd.h>
@@ -442,7 +442,7 @@ ProcQueueInit(PROC_QUEUE *queue)
* NOTES: The process queue is now a priority queue for locking.
*/
int
ProcSleep(PROC_QUEUE *queue,
ProcSleep(PROC_QUEUE *waitQueue,
SPINLOCK spinlock,
int token,
int prio,
@@ -453,8 +453,8 @@ ProcSleep(PROC_QUEUE *queue,
struct itimerval timeval,
dummy;
proc = (PROC *) MAKE_PTR(queue->links.prev);
for (i = 0; i < queue->size; i++)
proc = (PROC *) MAKE_PTR(waitQueue->links.prev);
for (i = 0; i < waitQueue->size; i++)
{
if (proc->prio >= prio)
proc = (PROC *) MAKE_PTR(proc->links.prev);
@@ -478,36 +478,38 @@ ProcSleep(PROC_QUEUE *queue,
* -------------------
*/
SHMQueueInsertTL(&(proc->links), &(MyProc->links));
queue->size++;
waitQueue->size++;
SpinRelease(spinlock);
/* --------------
* Postgres does not have any deadlock detection code and for this
* reason we must set a timer to wake up the process in the event of
* a deadlock. For now the timer is set for 1 minute and we assume that
* any process which sleeps for this amount of time is deadlocked and will
* receive a SIGALRM signal. The handler should release the processes
* semaphore and abort the current transaction.
* We set this so we can wake up periodically and check for a deadlock.
* If a deadlock is detected, the handler releases the processes
* semaphore and aborts the current transaction.
*
* Need to zero out struct to set the interval and the micro seconds fields
* to 0.
* --------------
*/
MemSet(&timeval, 0, sizeof(struct itimerval));
timeval.it_value.tv_sec = DEADLOCK_TIMEOUT;
timeval.it_value.tv_sec = DEADLOCK_CHECK_TIMER;
if (setitimer(ITIMER_REAL, &timeval, &dummy))
elog(FATAL, "ProcSleep: Unable to set timer for process wakeup");
do
{
MyProc->errType = NO_ERROR; /* reset flag after deadlock check */
/* --------------
* if someone wakes us between SpinRelease and IpcSemaphoreLock,
* IpcSemaphoreLock will not block. The wakeup is "saved" by
* the semaphore implementation.
* --------------
*/
IpcSemaphoreLock(MyProc->sem.semId, MyProc->sem.semNum, IpcExclusiveLock);
if (setitimer(ITIMER_REAL, &timeval, &dummy))
elog(FATAL, "ProcSleep: Unable to set timer for process wakeup");
/* --------------
* if someone wakes us between SpinRelease and IpcSemaphoreLock,
* IpcSemaphoreLock will not block. The wakeup is "saved" by
* the semaphore implementation.
* --------------
*/
IpcSemaphoreLock(MyProc->sem.semId, MyProc->sem.semNum, IpcExclusiveLock);
} while (MyProc->errType == STATUS_NOT_FOUND); /* sleep after deadlock check */
/* ---------------
* We were awoken before a timeout - now disable the timer
* ---------------
@@ -615,10 +617,9 @@ ProcAddLock(SHM_QUEUE *elem)
}
/* --------------------
* We only get to this routine if we got SIGALRM after DEADLOCK_TIMEOUT
* while waiting for a lock to be released by some other process. After
* the one minute deadline we assume we have a deadlock and must abort
* this transaction. We must also indicate that I'm no longer waiting
* We only get to this routine if we got SIGALRM after DEADLOCK_CHECK_TIMER
* while waiting for a lock to be released by some other process. If we have
* a real deadlock, we must also indicate that I'm no longer waiting
* on a lock so that other processes don't try to wake me up and screw
* up my semaphore.
* --------------------
@@ -665,12 +666,19 @@ HandleDeadLock(int sig)
return;
}
mywaitlock = MyProc->waitLock;
#ifdef DEADLOCK_DEBUG
DumpLocks();
#endif
if (!DeadLockCheck(&(MyProc->lockQueue), MyProc->waitLock, true))
{
UnlockLockTable();
MyProc->errType = STATUS_NOT_FOUND;
return;
}
mywaitlock = MyProc->waitLock;
/* ------------------------
* Get this process off the lock's wait queue
* ------------------------
@@ -701,8 +709,7 @@ HandleDeadLock(int sig)
*/
UnlockLockTable();
elog(NOTICE, "Timeout interval reached -- possible deadlock.");
elog(NOTICE, "See the lock(l) manual page for a possible cause.");
elog(NOTICE, "Deadlock detected -- See the lock(l) manual page for a possible cause.");
return;
}