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Commit9e7b9c6

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Fix newly introduced datetime.c compile failure; not enough parens.
1 parent48ad40b commit9e7b9c6

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2 files changed

+65
-60
lines changed

2 files changed

+65
-60
lines changed

‎src/backend/storage/lmgr/lwlock.c

Lines changed: 63 additions & 58 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@
1515
* Portions Copyright (c) 1994, Regents of the University of California
1616
*
1717
* IDENTIFICATION
18-
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lwlock.c,v 1.5 2001/12/28 23:26:04 tgl Exp $
18+
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lwlock.c,v 1.6 2001/12/29 21:28:18 momjian Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
@@ -195,7 +195,8 @@ void
195195
LWLockAcquire(LWLockIdlockid,LWLockModemode)
196196
{
197197
volatileLWLock*lock=LWLockArray+lockid;
198-
boolmustwait;
198+
PROC*proc=MyProc;
199+
intextraWaits=0;
199200

200201
PRINT_LWDEBUG("LWLockAcquire",lockid,lock);
201202

@@ -206,43 +207,57 @@ LWLockAcquire(LWLockId lockid, LWLockMode mode)
206207
*/
207208
HOLD_INTERRUPTS();
208209

209-
/* Acquire mutex. Time spent holding mutex should be short! */
210-
SpinLockAcquire_NoHoldoff(&lock->mutex);
211-
212-
/* If I can get the lock, do so quickly. */
213-
if (mode==LW_EXCLUSIVE)
210+
/*
211+
* Loop here to try to acquire lock after each time we are signaled
212+
* by LWLockRelease.
213+
*
214+
* NOTE: it might seem better to have LWLockRelease actually grant us
215+
* the lock, rather than retrying and possibly having to go back to
216+
* sleep. But in practice that is no good because it means a process
217+
* swap for every lock acquisition when two or more processes are
218+
* contending for the same lock. Since LWLocks are normally used to
219+
* protect not-very-long sections of computation, a process needs to
220+
* be able to acquire and release the same lock many times during a
221+
* single process dispatch cycle, even in the presence of contention.
222+
* The efficiency of being able to do that outweighs the inefficiency of
223+
* sometimes wasting a dispatch cycle because the lock is not free when a
224+
* released waiter gets to run. See pgsql-hackers archives for 29-Dec-01.
225+
*/
226+
for (;;)
214227
{
215-
if (lock->exclusive==0&&lock->shared==0)
228+
boolmustwait;
229+
230+
/* Acquire mutex. Time spent holding mutex should be short! */
231+
SpinLockAcquire_NoHoldoff(&lock->mutex);
232+
233+
/* If I can get the lock, do so quickly. */
234+
if (mode==LW_EXCLUSIVE)
216235
{
217-
lock->exclusive++;
218-
mustwait= false;
236+
if (lock->exclusive==0&&lock->shared==0)
237+
{
238+
lock->exclusive++;
239+
mustwait= false;
240+
}
241+
else
242+
mustwait= true;
219243
}
220244
else
221-
mustwait= true;
222-
}
223-
else
224-
{
225-
/*
226-
* If there is someone waiting (presumably for exclusive access),
227-
* queue up behind him even though I could get the lock. This
228-
* prevents a stream of read locks from starving a writer.
229-
*/
230-
if (lock->exclusive==0&&lock->head==NULL)
231245
{
232-
lock->shared++;
233-
mustwait= false;
246+
if (lock->exclusive==0)
247+
{
248+
lock->shared++;
249+
mustwait= false;
250+
}
251+
else
252+
mustwait= true;
234253
}
235-
else
236-
mustwait= true;
237-
}
238254

239-
if (mustwait)
240-
{
241-
/* Add myself to wait queue */
242-
PROC*proc=MyProc;
243-
intextraWaits=0;
255+
if (!mustwait)
256+
break;/* got the lock */
244257

245258
/*
259+
* Add myself to wait queue.
260+
*
246261
* If we don't have a PROC structure, there's no way to wait. This
247262
* should never occur, since MyProc should only be null during
248263
* shared memory initialization.
@@ -267,9 +282,9 @@ LWLockAcquire(LWLockId lockid, LWLockMode mode)
267282
*
268283
* Since we share the process wait semaphore with the regular lock
269284
* manager and ProcWaitForSignal, and we may need to acquire an
270-
* LWLock while one of those is pending, it is possible that we
271-
*getawakened for a reason other than beinggranted the LWLock.
272-
* If so, loop back and wait again. Once we've gotten thelock,
285+
* LWLock while one of those is pending, it is possible that we get
286+
* awakened for a reason other than beingsignaled by LWLockRelease.
287+
* If so, loop back and wait again. Once we've gotten theLWLock,
273288
* re-increment the sema by the number of additional signals
274289
* received, so that the lock manager or signal manager will see
275290
* the received signal when it next waits.
@@ -287,23 +302,21 @@ LWLockAcquire(LWLockId lockid, LWLockMode mode)
287302

288303
LOG_LWDEBUG("LWLockAcquire",lockid,"awakened");
289304

290-
/*
291-
* The awakener already updated the lock struct's state, so we
292-
* don't need to do anything more to it. Just need to fix the
293-
* semaphore count.
294-
*/
295-
while (extraWaits-->0)
296-
IpcSemaphoreUnlock(proc->sem.semId,proc->sem.semNum);
297-
}
298-
else
299-
{
300-
/* Got the lock without waiting */
301-
SpinLockRelease_NoHoldoff(&lock->mutex);
305+
/* Now loop back and try to acquire lock again. */
302306
}
303307

308+
/* We are done updating shared state of the lock itself. */
309+
SpinLockRelease_NoHoldoff(&lock->mutex);
310+
304311
/* Add lock to list of locks held by this backend */
305312
Assert(num_held_lwlocks<MAX_SIMUL_LWLOCKS);
306313
held_lwlocks[num_held_lwlocks++]=lockid;
314+
315+
/*
316+
* Fix the process wait semaphore's count for any absorbed wakeups.
317+
*/
318+
while (extraWaits-->0)
319+
IpcSemaphoreUnlock(proc->sem.semId,proc->sem.semNum);
307320
}
308321

309322
/*
@@ -344,12 +357,7 @@ LWLockConditionalAcquire(LWLockId lockid, LWLockMode mode)
344357
}
345358
else
346359
{
347-
/*
348-
* If there is someone waiting (presumably for exclusive access),
349-
* queue up behind him even though I could get the lock. This
350-
* prevents a stream of read locks from starving a writer.
351-
*/
352-
if (lock->exclusive==0&&lock->head==NULL)
360+
if (lock->exclusive==0)
353361
{
354362
lock->shared++;
355363
mustwait= false;
@@ -427,20 +435,17 @@ LWLockRelease(LWLockId lockid)
427435
if (lock->exclusive==0&&lock->shared==0)
428436
{
429437
/*
430-
* Remove the to-be-awakened PROCs from the queue, and update
431-
* the lock state to show them as holding the lock.
438+
* Remove the to-be-awakened PROCs from the queue. If the
439+
* front waiter wants exclusive lock, awaken him only.
440+
* Otherwise awaken as many waiters as want shared access.
432441
*/
433442
proc=head;
434-
if (proc->lwExclusive)
435-
lock->exclusive++;
436-
else
443+
if (!proc->lwExclusive)
437444
{
438-
lock->shared++;
439445
while (proc->lwWaitLink!=NULL&&
440446
!proc->lwWaitLink->lwExclusive)
441447
{
442448
proc=proc->lwWaitLink;
443-
lock->shared++;
444449
}
445450
}
446451
/* proc is now the last PROC to be released */

‎src/backend/utils/adt/datetime.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.84 2001/12/2918:40:58 thomas Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.85 2001/12/2921:28:18 momjian Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -959,7 +959,7 @@ DecodeDateTime(char **field, int *ftype, int nf,
959959
if (tzp==NULL)
960960
return-1;
961961

962-
if ((isdigit(*field[i])||(ptype!=0))
962+
if (isdigit(*field[i])||ptype!=0)
963963
{
964964
char*cp;
965965

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