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Prevent priority inversion in locking by checking for existing locks

before going into queue behind person with higher piority.
This commit is contained in:
Bruce Momjian
1999-04-30 02:04:51 +00:00
parent 7d62e9c719
commit 52f1b2f3b6
5 changed files with 34 additions and 34 deletions

View File

@ -6,7 +6,7 @@
# Copyright (c) 1998, Regents of the University of California
#
# IDENTIFICATION
# $Header: /cvsroot/pgsql/src/Makefile.shlib,v 1.7 1999/03/14 16:02:57 momjian Exp $
# $Header: /cvsroot/pgsql/src/Makefile.shlib,v 1.8 1999/04/30 02:04:49 momjian Exp $
#
#-------------------------------------------------------------------------
@ -86,14 +86,14 @@ ifeq ($(PORTNAME), bsdi)
ifdef BSD_SHLIB
ifeq ($(DLSUFFIX), .so)
install-shlib-dep := install-shlib
shlib := lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION).$(SO_MINOR_VERSION)
shlib := lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION).$(SO_MINOR_VERSION)
LDFLAGS_SL += -shared
CFLAGS += $(CFLAGS_SL)
endif
ifeq ($(DLSUFFIX), .o)
install-shlib-dep := install-shlib
shlib := lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION).$(SO_MINOR_VERSION)
LD := shlicc
shlib := lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION).$(SO_MINOR_VERSION)
LD := shlicc
LDFLAGS_SL += -O -r
CFLAGS += $(CFLAGS_SL)
endif

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@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.46 1999/03/06 21:17:44 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.47 1999/04/30 02:04:50 momjian Exp $
*
* NOTES
* Outside modules can create a lock table and acquire/release
@ -820,13 +820,17 @@ LockResolveConflicts(LOCKMETHOD lockmethod,
/* ------------------------
* If someone with a greater priority is waiting for the lock,
* do not continue and share the lock, even if we can. bjm
* Don't do this if the process already has some locks, because
* this could hold up other people waiting on our locks, causing
* a priority inversion. bjm
* ------------------------
*/
int myprio = LockMethodTable[lockmethod]->ctl->prio[lockmode];
PROC_QUEUE *waitQueue = &(lock->waitProcs);
PROC *topproc = (PROC *) MAKE_PTR(waitQueue->links.prev);
if (waitQueue->size && topproc->prio > myprio)
if (SHMQueueEmpty(lockQueue) && waitQueue->size &&
topproc->prio > myprio)
{
XID_PRINT("LockResolveConflicts: higher priority proc waiting",
result);
@ -1595,7 +1599,7 @@ DeadLockCheck(SHM_QUEUE *lockQueue, LOCK *findlock, bool skip_check)
*
* The lock we are waiting for is already in MyProc->lockQueue so we
* need to skip it here. We are trying to find it in someone
* else's lockQueue.
* else's lockQueue. bjm
*/
if (lock == findlock && !skip_check)
return true;
@ -1625,7 +1629,7 @@ DeadLockCheck(SHM_QUEUE *lockQueue, LOCK *findlock, bool skip_check)
*
* Basically, the test is, "Do we both hold some lock on
* findlock, and we are both waiting in the lock
* queue?"
* queue?" bjm
*/
Assert(skip_check);
@ -1672,7 +1676,7 @@ DeadLockCheck(SHM_QUEUE *lockQueue, LOCK *findlock, bool skip_check)
* hold locks and are waiting. Now we check for
* cases where we have two or more tables in a
* deadlock. We do this by continuing to search
* for someone holding a lock
* for someone holding a lock bjm
*/
if (DeadLockCheck(&(proc->lockQueue), findlock, false))
return true;

View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.52 1999/03/28 20:32:26 vadim Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.53 1999/04/30 02:04:51 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 1.52 1999/03/28 20:32:26 vadim Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.53 1999/04/30 02:04:51 momjian Exp $
*/
#include <sys/time.h>
#include <unistd.h>
@ -516,8 +516,7 @@ ProcSleep(PROC_QUEUE *waitQueue,/* lock->waitProcs */
* In a full queue, we would have a reader holding a lock, then a writer
* gets the lock, then a bunch of readers, made up of readers who
* could not share the first readlock because a writer was waiting,
* and new readers arriving while the writer had the lock.
*
* and new readers arriving while the writer had the lock. bjm
*/
proc = (PROC *) MAKE_PTR(waitQueue->links.prev);