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Make it easier to choose the used waiting primitive in unix_latch.c.

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This allows for easier testing of the different primitives; in
preparation for adding a new primitive.

Discussion: 20160114143931.GG10941@awork2.anarazel.de
Reviewed-By: Robert Haas
This commit is contained in:
Andres Freund 2016-03-18 11:43:59 -07:00
parent 6bc4d95fcc
commit c17966201c
1 changed files with 34 additions and 16 deletions
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50
src/backend/port/unix_latch.c
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@ -56,6 +56,22 @@
#include "storage/pmsignal.h"
#include "storage/shmem.h"
/*
* Select the fd readiness primitive to use. Normally the "most modern"
* primitive supported by the OS will be used, but for testing it can be
* useful to manually specify the used primitive. If desired, just add a
* define somewhere before this block.
*/
#if defined(LATCH_USE_POLL) || defined(LATCH_USE_SELECT)
/* don't overwrite manual choice */
#elif defined(HAVE_POLL)
#define LATCH_USE_POLL
#elif HAVE_SYS_SELECT_H
#define LATCH_USE_SELECT
#else
#error "no latch implementation available"
#endif
/* Are we currently in WaitLatch? The signal handler would like to know. */
static volatile sig_atomic_t waiting = false;
@ -215,10 +231,10 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
cur_time;
long cur_timeout;
#ifdef HAVE_POLL
#if defined(LATCH_USE_POLL)
struct pollfd pfds[3];
int nfds;
#else
#elif defined(LATCH_USE_SELECT)
struct timeval tv,
*tvp;
fd_set input_mask;
@ -248,7 +264,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
Assert(timeout >= 0 && timeout <= INT_MAX);
cur_timeout = timeout;
#ifndef HAVE_POLL
#ifdef LATCH_USE_SELECT
tv.tv_sec = cur_timeout / 1000L;
tv.tv_usec = (cur_timeout % 1000L) * 1000L;
tvp = &tv;
@ -258,7 +274,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
{
cur_timeout = -1;
#ifndef HAVE_POLL
#ifdef LATCH_USE_SELECT
tvp = NULL;
#endif
}
@ -292,16 +308,10 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
}
/*
* Must wait ... we use poll(2) if available, otherwise select(2).
*
* On at least older linux kernels select(), in violation of POSIX,
* doesn't reliably return a socket as writable if closed - but we
* rely on that. So far all the known cases of this problem are on
* platforms that also provide a poll() implementation without that
* bug. If we find one where that's not the case, we'll need to add a
* workaround.
* Must wait ... we use the polling interface determined at the top of
* this file to do so.
*/
#ifdef HAVE_POLL
#if defined(LATCH_USE_POLL)
nfds = 0;
if (wakeEvents & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE))
{
@ -397,8 +407,16 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
result |= WL_POSTMASTER_DEATH;
}
}
#else /* !HAVE_POLL */
#elif defined(LATCH_USE_SELECT)
/*
* On at least older linux kernels select(), in violation of POSIX,
* doesn't reliably return a socket as writable if closed - but we
* rely on that. So far all the known cases of this problem are on
* platforms that also provide a poll() implementation without that
* bug. If we find one where that's not the case, we'll need to add a
* workaround.
*/
FD_ZERO(&input_mask);
FD_ZERO(&output_mask);
@ -478,7 +496,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
result |= WL_POSTMASTER_DEATH;
}
}
#endif /* HAVE_POLL */
#endif /* LATCH_USE_SELECT */
/* If we're not done, update cur_timeout for next iteration */
if (result == 0 && (wakeEvents & WL_TIMEOUT))
@ -491,7 +509,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
/* Timeout has expired, no need to continue looping */
result |= WL_TIMEOUT;
}
#ifndef HAVE_POLL
#ifdef LATCH_USE_SELECT
else
{
tv.tv_sec = cur_timeout / 1000L;