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Commitc179662

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Make it easier to choose the used waiting primitive in unix_latch.c.
This allows for easier testing of the different primitives; inpreparation for adding a new primitive.Discussion: 20160114143931.GG10941@awork2.anarazel.deReviewed-By: Robert Haas
1 parent6bc4d95 commitc179662

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1 file changed

+34
-16
lines changed

1 file changed

+34
-16
lines changed

‎src/backend/port/unix_latch.c

Lines changed: 34 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -56,6 +56,22 @@
5656
#include"storage/pmsignal.h"
5757
#include"storage/shmem.h"
5858

59+
/*
60+
* Select the fd readiness primitive to use. Normally the "most modern"
61+
* primitive supported by the OS will be used, but for testing it can be
62+
* useful to manually specify the used primitive. If desired, just add a
63+
* define somewhere before this block.
64+
*/
65+
#if defined(LATCH_USE_POLL)|| defined(LATCH_USE_SELECT)
66+
/* don't overwrite manual choice */
67+
#elif defined(HAVE_POLL)
68+
#defineLATCH_USE_POLL
69+
#elifHAVE_SYS_SELECT_H
70+
#defineLATCH_USE_SELECT
71+
#else
72+
#error "no latch implementation available"
73+
#endif
74+
5975
/* Are we currently in WaitLatch? The signal handler would like to know. */
6076
staticvolatilesig_atomic_twaiting= false;
6177

@@ -215,10 +231,10 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
215231
cur_time;
216232
longcur_timeout;
217233

218-
#ifdefHAVE_POLL
234+
#if defined(LATCH_USE_POLL)
219235
structpollfdpfds[3];
220236
intnfds;
221-
#else
237+
#elif defined(LATCH_USE_SELECT)
222238
structtimevaltv,
223239
*tvp;
224240
fd_setinput_mask;
@@ -248,7 +264,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
248264
Assert(timeout >=0&&timeout <=INT_MAX);
249265
cur_timeout=timeout;
250266

251-
#ifndefHAVE_POLL
267+
#ifdefLATCH_USE_SELECT
252268
tv.tv_sec=cur_timeout /1000L;
253269
tv.tv_usec= (cur_timeout %1000L)*1000L;
254270
tvp=&tv;
@@ -258,7 +274,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
258274
{
259275
cur_timeout=-1;
260276

261-
#ifndefHAVE_POLL
277+
#ifdefLATCH_USE_SELECT
262278
tvp=NULL;
263279
#endif
264280
}
@@ -292,16 +308,10 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
292308
}
293309

294310
/*
295-
* Must wait ... we use poll(2) if available, otherwise select(2).
296-
*
297-
* On at least older linux kernels select(), in violation of POSIX,
298-
* doesn't reliably return a socket as writable if closed - but we
299-
* rely on that. So far all the known cases of this problem are on
300-
* platforms that also provide a poll() implementation without that
301-
* bug. If we find one where that's not the case, we'll need to add a
302-
* workaround.
311+
* Must wait ... we use the polling interface determined at the top of
312+
* this file to do so.
303313
*/
304-
#ifdefHAVE_POLL
314+
#if defined(LATCH_USE_POLL)
305315
nfds=0;
306316
if (wakeEvents& (WL_SOCKET_READABLE |WL_SOCKET_WRITEABLE))
307317
{
@@ -397,8 +407,16 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
397407
result |=WL_POSTMASTER_DEATH;
398408
}
399409
}
400-
#else/* !HAVE_POLL */
410+
#elif defined(LATCH_USE_SELECT)
401411

412+
/*
413+
* On at least older linux kernels select(), in violation of POSIX,
414+
* doesn't reliably return a socket as writable if closed - but we
415+
* rely on that. So far all the known cases of this problem are on
416+
* platforms that also provide a poll() implementation without that
417+
* bug. If we find one where that's not the case, we'll need to add a
418+
* workaround.
419+
*/
402420
FD_ZERO(&input_mask);
403421
FD_ZERO(&output_mask);
404422

@@ -478,7 +496,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
478496
result |=WL_POSTMASTER_DEATH;
479497
}
480498
}
481-
#endif/*HAVE_POLL */
499+
#endif/*LATCH_USE_SELECT */
482500

483501
/* If we're not done, update cur_timeout for next iteration */
484502
if (result==0&& (wakeEvents&WL_TIMEOUT))
@@ -491,7 +509,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
491509
/* Timeout has expired, no need to continue looping */
492510
result |=WL_TIMEOUT;
493511
}
494-
#ifndefHAVE_POLL
512+
#ifdefLATCH_USE_SELECT
495513
else
496514
{
497515
tv.tv_sec=cur_timeout /1000L;

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