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Commit7f60b81

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Fix failure in CreateCheckPoint on some Alpha boxes --- it's not OK to
assume that TAS() will always succeed the first time, even if the lockis known to be free. Also, make sure that code will eventually time outand report a stuck spinlock, rather than looping forever. Small cleanupsin s_lock.h, too.
1 parent7d363c4 commit7f60b81

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4 files changed

+194
-177
lines changed

4 files changed

+194
-177
lines changed

‎src/backend/access/transam/xlog.c

Lines changed: 27 additions & 55 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
9-
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.45 2000/12/28 13:00:08 vadim Exp $
9+
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.46 2000/12/29 21:31:21 tgl Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -411,7 +411,7 @@ begin:;
411411
}
412412
}
413413
}
414-
s_lock_sleep(i++);
414+
S_LOCK_SLEEP(&(XLogCtl->insert_lck),i++);
415415
if (!TAS(&(XLogCtl->insert_lck)))
416416
break;
417417
}
@@ -599,17 +599,10 @@ begin:;
599599

600600
if (updrqst)
601601
{
602-
for (;;)
603-
{
604-
if (!TAS(&(XLogCtl->info_lck)))
605-
{
606-
if (XLByteLT(XLogCtl->LgwrRqst.Write,LgwrRqst.Write))
607-
XLogCtl->LgwrRqst.Write=LgwrRqst.Write;
608-
S_UNLOCK(&(XLogCtl->info_lck));
609-
break;
610-
}
611-
s_lock_sleep(i++);
612-
}
602+
S_LOCK(&(XLogCtl->info_lck));
603+
if (XLByteLT(XLogCtl->LgwrRqst.Write,LgwrRqst.Write))
604+
XLogCtl->LgwrRqst.Write=LgwrRqst.Write;
605+
S_UNLOCK(&(XLogCtl->info_lck));
613606
}
614607

615608
END_CRIT_CODE;
@@ -622,7 +615,7 @@ XLogFlush(XLogRecPtr record)
622615
XLogRecPtrWriteRqst;
623616
charbuffer[BLCKSZ];
624617
char*usebuf=NULL;
625-
unsignedi=0;
618+
unsignedspins=0;
626619
boolforce_lgwr= false;
627620

628621
if (XLOG_DEBUG)
@@ -715,7 +708,7 @@ XLogFlush(XLogRecPtr record)
715708
break;
716709
}
717710
}
718-
s_lock_sleep(i++);
711+
S_LOCK_SLEEP(&(XLogCtl->lgwr_lck),spins++);
719712
}
720713

721714
if (logFile >=0&& (LgwrResult.Write.xlogid!=logId||
@@ -740,18 +733,12 @@ XLogFlush(XLogRecPtr record)
740733
logId,logSeg);
741734
LgwrResult.Flush=LgwrResult.Write;
742735

743-
for (i=0;;)
744-
{
745-
if (!TAS(&(XLogCtl->info_lck)))
746-
{
747-
XLogCtl->LgwrResult=LgwrResult;
748-
if (XLByteLT(XLogCtl->LgwrRqst.Write,LgwrResult.Write))
749-
XLogCtl->LgwrRqst.Write=LgwrResult.Write;
750-
S_UNLOCK(&(XLogCtl->info_lck));
751-
break;
752-
}
753-
s_lock_sleep(i++);
754-
}
736+
S_LOCK(&(XLogCtl->info_lck));
737+
XLogCtl->LgwrResult=LgwrResult;
738+
if (XLByteLT(XLogCtl->LgwrRqst.Write,LgwrResult.Write))
739+
XLogCtl->LgwrRqst.Write=LgwrResult.Write;
740+
S_UNLOCK(&(XLogCtl->info_lck));
741+
755742
XLogCtl->Write.LgwrResult=LgwrResult;
756743

757744
S_UNLOCK(&(XLogCtl->lgwr_lck));
@@ -767,6 +754,7 @@ GetFreeXLBuffer()
767754
XLogCtlInsert*Insert=&XLogCtl->Insert;
768755
XLogCtlWrite*Write=&XLogCtl->Write;
769756
uint16curridx=NextBufIdx(Insert->curridx);
757+
unsignedspins=0;
770758

771759
LgwrRqst.Write=XLogCtl->xlblocks[Insert->curridx];
772760
for (;;)
@@ -809,9 +797,8 @@ GetFreeXLBuffer()
809797
InitXLBuffer(curridx);
810798
return;
811799
}
800+
S_LOCK_SLEEP(&(XLogCtl->lgwr_lck),spins++);
812801
}
813-
814-
return;
815802
}
816803

817804
staticvoid
@@ -820,7 +807,6 @@ XLogWrite(char *buffer)
820807
XLogCtlWrite*Write=&XLogCtl->Write;
821808
char*from;
822809
uint32wcnt=0;
823-
inti=0;
824810
boolusexistent;
825811

826812
for (;XLByteLT(LgwrResult.Write,LgwrRqst.Write);)
@@ -919,18 +905,12 @@ XLogWrite(char *buffer)
919905
LgwrResult.Flush=LgwrResult.Write;
920906
}
921907

922-
for (;;)
923-
{
924-
if (!TAS(&(XLogCtl->info_lck)))
925-
{
926-
XLogCtl->LgwrResult=LgwrResult;
927-
if (XLByteLT(XLogCtl->LgwrRqst.Write,LgwrResult.Write))
928-
XLogCtl->LgwrRqst.Write=LgwrResult.Write;
929-
S_UNLOCK(&(XLogCtl->info_lck));
930-
break;
931-
}
932-
s_lock_sleep(i++);
933-
}
908+
S_LOCK(&(XLogCtl->info_lck));
909+
XLogCtl->LgwrResult=LgwrResult;
910+
if (XLByteLT(XLogCtl->LgwrRqst.Write,LgwrResult.Write))
911+
XLogCtl->LgwrRqst.Write=LgwrResult.Write;
912+
S_UNLOCK(&(XLogCtl->info_lck));
913+
934914
Write->LgwrResult=LgwrResult;
935915
}
936916

@@ -2062,18 +2042,17 @@ CreateCheckPoint(bool shutdown)
20622042
uint32_logId;
20632043
uint32_logSeg;
20642044
chararchdir[MAXPGPATH];
2045+
unsignedspins=0;
20652046

20662047
if (MyLastRecPtr.xrecoff!=0)
20672048
elog(ERROR,"CreateCheckPoint: cannot be called inside transaction block");
20682049

20692050
START_CRIT_CODE;
2051+
2052+
/* Grab lock, using larger than normal sleep between tries (1 sec) */
20702053
while (TAS(&(XLogCtl->chkp_lck)))
20712054
{
2072-
structtimevaldelay= {2,0};
2073-
2074-
if (shutdown)
2075-
elog(STOP,"Checkpoint lock is busy while data base is shutting down");
2076-
(void)select(0,NULL,NULL,NULL,&delay);
2055+
S_LOCK_SLEEP_INTERVAL(&(XLogCtl->chkp_lck),spins++,1000000);
20772056
}
20782057

20792058
memset(&checkPoint,0,sizeof(checkPoint));
@@ -2087,14 +2066,7 @@ CreateCheckPoint(bool shutdown)
20872066
checkPoint.Shutdown=shutdown;
20882067

20892068
/* Get REDO record ptr */
2090-
while (TAS(&(XLogCtl->insert_lck)))
2091-
{
2092-
structtimevaldelay= {1,0};
2093-
2094-
if (shutdown)
2095-
elog(STOP,"XLog insert lock is busy while data base is shutting down");
2096-
(void)select(0,NULL,NULL,NULL,&delay);
2097-
}
2069+
S_LOCK(&(XLogCtl->insert_lck));
20982070
freespace= ((char*)Insert->currpage)+BLCKSZ-Insert->currpos;
20992071
if (freespace<SizeOfXLogRecord)
21002072
{

‎src/backend/storage/buffer/bufmgr.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.100 2000/12/28 13:00:21vadim Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.101 2000/12/29 21:31:21tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1987,7 +1987,7 @@ LockBuffer(Buffer buffer, int mode)
19871987
while (buf->ri_lock||buf->w_lock)
19881988
{
19891989
S_UNLOCK(&(buf->cntx_lock));
1990-
s_lock_sleep(i++);
1990+
S_LOCK_SLEEP(&(buf->cntx_lock),i++);
19911991
S_LOCK(&(buf->cntx_lock));
19921992
}
19931993
(buf->r_locks)++;
@@ -2013,7 +2013,7 @@ LockBuffer(Buffer buffer, int mode)
20132013
buf->ri_lock= true;
20142014
}
20152015
S_UNLOCK(&(buf->cntx_lock));
2016-
s_lock_sleep(i++);
2016+
S_LOCK_SLEEP(&(buf->cntx_lock),i++);
20172017
S_LOCK(&(buf->cntx_lock));
20182018
}
20192019
buf->w_lock= true;

‎src/backend/storage/buffer/s_lock.c

Lines changed: 39 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/Attic/s_lock.c,v 1.27 2000/12/11 00:49:51 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/Attic/s_lock.c,v 1.28 2000/12/29 21:31:20 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -25,19 +25,21 @@
2525
* number of microseconds to wait. This accomplishes pseudo random back-off.
2626
* Values are not critical but 10 milliseconds is a common platform
2727
* granularity.
28-
* note: total time to cycle through all 16 entries might be about .07 sec.
28+
*
29+
* Total time to cycle through all 20 entries might be about .07 sec,
30+
* so the given value of S_MAX_BUSY results in timeout after ~70 sec.
2931
*/
3032
#defineS_NSPINCYCLE20
3133
#defineS_MAX_BUSY1000 * S_NSPINCYCLE
3234

3335
ints_spincycle[S_NSPINCYCLE]=
34-
{0,0,0,0,10000,0,0,0,10000,0,
36+
{0,0,0,0,10000,0,0,0,10000,0,
3537
0,10000,0,0,10000,0,10000,0,10000,10000
3638
};
3739

3840

3941
/*
40-
* s_lock_stuck(lock) - complain about a stuck spinlock
42+
* s_lock_stuck() - complain about a stuck spinlock
4143
*/
4244
staticvoid
4345
s_lock_stuck(volatileslock_t*lock,constchar*file,constintline)
@@ -52,13 +54,38 @@ s_lock_stuck(volatile slock_t *lock, const char *file, const int line)
5254
}
5355

5456

57+
/*
58+
* s_lock_sleep() - sleep a pseudo-random amount of time, check for timeout
59+
*
60+
* Normally 'microsec' is 0, specifying to use the next s_spincycle[] value.
61+
* Some callers may pass a nonzero interval, specifying to use exactly that
62+
* delay value rather than a pseudo-random delay.
63+
*/
5564
void
56-
s_lock_sleep(unsignedspin)
65+
s_lock_sleep(unsignedspins,intmicrosec,
66+
volatileslock_t*lock,
67+
constchar*file,constintline)
5768
{
5869
structtimevaldelay;
70+
unsignedmax_spins;
71+
72+
if (microsec>0)
73+
{
74+
delay.tv_sec=0;
75+
delay.tv_usec=microsec;
76+
/* two-minute timeout in this case */
77+
max_spins=120000000 /microsec;
78+
}
79+
else
80+
{
81+
delay.tv_sec=0;
82+
delay.tv_usec=s_spincycle[spins %S_NSPINCYCLE];
83+
max_spins=S_MAX_BUSY;
84+
}
85+
86+
if (spins>max_spins)
87+
s_lock_stuck(lock,file,line);
5988

60-
delay.tv_sec=0;
61-
delay.tv_usec=s_spincycle[spin %S_NSPINCYCLE];
6289
(void)select(0,NULL,NULL,NULL,&delay);
6390
}
6491

@@ -71,14 +98,13 @@ s_lock(volatile slock_t *lock, const char *file, const int line)
7198
{
7299
unsignedspins=0;
73100

101+
/*
102+
* If you are thinking of changing this code, be careful. This same
103+
* loop logic is used in other places that call TAS() directly.
104+
*/
74105
while (TAS(lock))
75106
{
76-
s_lock_sleep(spins);
77-
if (++spins>S_MAX_BUSY)
78-
{
79-
/* It's been over a minute... */
80-
s_lock_stuck(lock,file,line);
81-
}
107+
s_lock_sleep(spins++,0,lock,file,line);
82108
}
83109
}
84110

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