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Commit35166fd

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Fix --disable-spinlocks in 9.2 and 9.3 branches.
My back-patch of the 9.4-era commit44cd47c into 9.2 and 9.3 fixedHPPA builds as expected, but it broke --disable-spinlocks builds, becausethe dummy spinlock is initialized before the underlying semaphoreinfrastructure is alive. In 9.4 and up this works because of commitdaa7527, which decoupled initialization of an slock_t variablefrom access to the actual system semaphore object. The best solutionseems to be to back-port that patch, which should be a net win anywaybecause it improves the usability of --disable-spinlocks builds in theolder branches; and it's been out long enough now to not be worrisomefrom a stability perspective.
1 parent0a32768 commit35166fd

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7 files changed

+80
-25
lines changed

7 files changed

+80
-25
lines changed

‎src/backend/postmaster/postmaster.c

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -500,6 +500,9 @@ typedef struct
500500
slock_t*ShmemLock;
501501
VariableCacheShmemVariableCache;
502502
Backend*ShmemBackendArray;
503+
#ifndefHAVE_SPINLOCKS
504+
PGSemaphoreSpinlockSemaArray;
505+
#endif
503506
LWLock*LWLockArray;
504507
slock_t*ProcStructLock;
505508
PROC_HDR*ProcGlobal;
@@ -6050,6 +6053,9 @@ save_backend_variables(BackendParameters *param, Port *port,
60506053
param->ShmemVariableCache=ShmemVariableCache;
60516054
param->ShmemBackendArray=ShmemBackendArray;
60526055

6056+
#ifndefHAVE_SPINLOCKS
6057+
param->SpinlockSemaArray=SpinlockSemaArray;
6058+
#endif
60536059
param->LWLockArray=LWLockArray;
60546060
param->ProcStructLock=ProcStructLock;
60556061
param->ProcGlobal=ProcGlobal;
@@ -6278,6 +6284,9 @@ restore_backend_variables(BackendParameters *param, Port *port)
62786284
ShmemVariableCache=param->ShmemVariableCache;
62796285
ShmemBackendArray=param->ShmemBackendArray;
62806286

6287+
#ifndefHAVE_SPINLOCKS
6288+
SpinlockSemaArray=param->SpinlockSemaArray;
6289+
#endif
62816290
LWLockArray=param->LWLockArray;
62826291
ProcStructLock=param->ProcStructLock;
62836292
ProcGlobal=param->ProcGlobal;

‎src/backend/storage/ipc/ipci.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -103,6 +103,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
103103
* need to be so careful during the actual allocation phase.
104104
*/
105105
size=100000;
106+
size=add_size(size,SpinlockSemaSize());
106107
size=add_size(size,hash_estimate_size(SHMEM_INDEX_SIZE,
107108
sizeof(ShmemIndexEnt)));
108109
size=add_size(size,BufferShmemSize());

‎src/backend/storage/ipc/shmem.c

Lines changed: 18 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -116,9 +116,24 @@ InitShmemAllocation(void)
116116
Assert(shmhdr!=NULL);
117117

118118
/*
119-
* Initialize the spinlock used by ShmemAlloc. We have to do the space
120-
* allocation the hard way, since obviously ShmemAlloc can't be called
121-
* yet.
119+
* If spinlocks are disabled, initialize emulation layer. We have to do
120+
* the space allocation the hard way, since obviously ShmemAlloc can't be
121+
* called yet.
122+
*/
123+
#ifndefHAVE_SPINLOCKS
124+
{
125+
PGSemaphorespinsemas;
126+
127+
spinsemas= (PGSemaphore) (((char*)shmhdr)+shmhdr->freeoffset);
128+
shmhdr->freeoffset+=MAXALIGN(SpinlockSemaSize());
129+
SpinlockSemaInit(spinsemas);
130+
Assert(shmhdr->freeoffset <=shmhdr->totalsize);
131+
}
132+
#endif
133+
134+
/*
135+
* Initialize the spinlock used by ShmemAlloc; we have to do this the hard
136+
* way, too, for the same reasons as above.
122137
*/
123138
ShmemLock= (slock_t*) (((char*)shmhdr)+shmhdr->freeoffset);
124139
shmhdr->freeoffset+=MAXALIGN(sizeof(slock_t));

‎src/backend/storage/lmgr/spin.c

Lines changed: 34 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -25,9 +25,24 @@
2525
#include"miscadmin.h"
2626
#include"replication/walsender.h"
2727
#include"storage/lwlock.h"
28+
#include"storage/pg_sema.h"
2829
#include"storage/spin.h"
2930

3031

32+
#ifndefHAVE_SPINLOCKS
33+
PGSemaphoreSpinlockSemaArray;
34+
#endif
35+
36+
/*
37+
* Report the amount of shared memory needed to store semaphores for spinlock
38+
* support.
39+
*/
40+
Size
41+
SpinlockSemaSize(void)
42+
{
43+
returnSpinlockSemas()*sizeof(PGSemaphoreData);
44+
}
45+
3146
#ifdefHAVE_SPINLOCKS
3247

3348
/*
@@ -51,21 +66,20 @@ SpinlockSemas(void)
5166
int
5267
SpinlockSemas(void)
5368
{
54-
intnsemas;
55-
56-
/*
57-
* It would be cleaner to distribute this logic into the affected modules,
58-
* similar to the way shmem space estimation is handled.
59-
*
60-
* For now, though, there are few enough users of spinlocks that we just
61-
* keep the knowledge here.
62-
*/
63-
nsemas=NumLWLocks();/* one for each lwlock */
64-
nsemas+=NBuffers;/* one for each buffer header */
65-
nsemas+=max_wal_senders;/* one for each wal sender process */
66-
nsemas+=30;/* plus a bunch for other small-scale use */
67-
68-
returnnsemas;
69+
returnNUM_SPINLOCK_SEMAPHORES;
70+
}
71+
72+
/*
73+
* Initialize semaphores.
74+
*/
75+
externvoid
76+
SpinlockSemaInit(PGSemaphorespinsemas)
77+
{
78+
inti;
79+
80+
for (i=0;i<NUM_SPINLOCK_SEMAPHORES;++i)
81+
PGSemaphoreCreate(&spinsemas[i]);
82+
SpinlockSemaArray=spinsemas;
6983
}
7084

7185
/*
@@ -75,13 +89,15 @@ SpinlockSemas(void)
7589
void
7690
s_init_lock_sema(volatileslock_t*lock)
7791
{
78-
PGSemaphoreCreate((PGSemaphore)lock);
92+
staticintcounter=0;
93+
94+
*lock= (++counter) %NUM_SPINLOCK_SEMAPHORES;
7995
}
8096

8197
void
8298
s_unlock_sema(volatileslock_t*lock)
8399
{
84-
PGSemaphoreUnlock((PGSemaphore)lock);
100+
PGSemaphoreUnlock(&SpinlockSemaArray[*lock]);
85101
}
86102

87103
bool
@@ -96,7 +112,7 @@ int
96112
tas_sema(volatileslock_t*lock)
97113
{
98114
/* Note that TAS macros return 0 if *success* */
99-
return !PGSemaphoreTryLock((PGSemaphore)lock);
115+
return !PGSemaphoreTryLock(&SpinlockSemaArray[*lock]);
100116
}
101117

102118
#endif/* !HAVE_SPINLOCKS */

‎src/include/pg_config_manual.h

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -56,6 +56,14 @@
5656
*/
5757
#defineNUM_USER_DEFINED_LWLOCKS4
5858

59+
/*
60+
* When we don't have native spinlocks, we use semaphores to simulate them.
61+
* Decreasing this value reduces consumption of OS resources; increasing it
62+
* may improve performance, but supplying a real spinlock implementation is
63+
* probably far better.
64+
*/
65+
#defineNUM_SPINLOCK_SEMAPHORES1024
66+
5967
/*
6068
* Define this if you want to allow the lo_import and lo_export SQL
6169
* functions to be executed by ordinary users. By default these

‎src/include/storage/s_lock.h

Lines changed: 1 addition & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -94,11 +94,8 @@
9494
#ifndefS_LOCK_H
9595
#defineS_LOCK_H
9696

97-
#include"storage/pg_sema.h"
98-
9997
#ifdefHAVE_SPINLOCKS/* skip spinlocks if requested */
10098

101-
10299
#if defined(__GNUC__)|| defined(__INTEL_COMPILER)
103100
/*************************************************************************
104101
* All the gcc inlines
@@ -1032,7 +1029,7 @@ spin_delay(void)
10321029
* to fall foul of kernel limits on number of semaphores, so don't use this
10331030
* unless you must! The subroutines appear in spin.c.
10341031
*/
1035-
typedefPGSemaphoreDataslock_t;
1032+
typedefintslock_t;
10361033

10371034
externbools_lock_free_sema(volatileslock_t*lock);
10381035
externvoids_unlock_sema(volatileslock_t*lock);

‎src/include/storage/spin.h

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,9 @@
5757
#defineSPIN_H
5858

5959
#include"storage/s_lock.h"
60+
#ifndefHAVE_SPINLOCKS
61+
#include"storage/pg_sema.h"
62+
#endif
6063

6164

6265
#defineSpinLockInit(lock)S_INIT_LOCK(lock)
@@ -69,5 +72,11 @@
6972

7073

7174
externintSpinlockSemas(void);
75+
externSizeSpinlockSemaSize(void);
76+
77+
#ifndefHAVE_SPINLOCKS
78+
externvoidSpinlockSemaInit(PGSemaphore);
79+
externPGSemaphoreSpinlockSemaArray;
80+
#endif
7281

7382
#endif/* SPIN_H */

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