Movatterモバイル変換


[0]ホーム

URL:


Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

Sign up
Appearance settings

Commitd2074da

Browse files
committed
In libpq for Windows, call WSAStartup once and WSACleanup not at all.
The Windows documentation insists that every WSAStartup call shouldhave a matching WSACleanup call. However, if that ever had actualrelevance, it wasn't in this century. Every remotely-modern Windowskernel is capable of cleaning up when a process exits without doingthat, and must be so to avoid resource leaks in case of a processcrash. Moreover, Postgres backends have done WSAStartup withoutWSACleanup since commit4cdf51e in 2004, and we've never seen anyindication of a problem with that.libpq's habit of doing WSAStartup during connection start andWSACleanup during shutdown is also rather inefficient, since aseries of non-overlapping connection requests leads to repeated,quite expensive DLL unload/reload cycles. We document a workaroundfor that (having the application call WSAStartup for itself), butthat's just a kluge. It's also worth noting that it's far fromuncommon for applications to exit without doing PQfinish, andwe've not heard reports of trouble from that either.However, the real reason for acting on this is that recentexperiments by Alexander Lakhin show that calling WSACleanupduring PQfinish is triggering the symptom we occasionally seethat a process using libpq fails to emit expected stdio output.Therefore, let's change libpq so that it calls WSAStartup onlyonce per process, during the first connection attempt, and nevercalls WSACleanup at all.While at it, get rid of the only other WSACleanup call in our codetree, in pg_dump/parallel.c; that presumably is equally useless.Back-patch of HEAD commit 7d00a6b2d.Discussion:https://postgr.es/m/ac976d8c-03df-d6b8-025c-15a2de8d9af1@postgrespro.ru
1 parentf2f03f9 commitd2074da

File tree

3 files changed

+18
-44
lines changed

3 files changed

+18
-44
lines changed

‎doc/src/sgml/libpq.sgml

Lines changed: 0 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -91,21 +91,6 @@
9191
</para>
9292
</warning>
9393

94-
<note>
95-
<para>
96-
On Windows, there is a way to improve performance if a single
97-
database connection is repeatedly started and shutdown. Internally,
98-
libpq calls <function>WSAStartup()</function> and <function>WSACleanup()</function> for connection startup
99-
and shutdown, respectively. <function>WSAStartup()</function> increments an internal
100-
Windows library reference count which is decremented by <function>WSACleanup()</function>.
101-
When the reference count is just one, calling <function>WSACleanup()</function> frees
102-
all resources and all DLLs are unloaded. This is an expensive
103-
operation. To avoid this, an application can manually call
104-
<function>WSAStartup()</function> so resources will not be freed when the last database
105-
connection is closed.
106-
</para>
107-
</note>
108-
10994
<variablelist>
11095
<varlistentry id="libpq-PQconnectdbParams">
11196
<term><function>PQconnectdbParams</function><indexterm><primary>PQconnectdbParams</primary></indexterm></term>

‎src/bin/pg_dump/parallel.c

Lines changed: 1 addition & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -229,19 +229,6 @@ static char *readMessageFromPipe(int fd);
229229
(strncmp(msg, prefix, strlen(prefix)) == 0)
230230

231231

232-
/*
233-
* Shutdown callback to clean up socket access
234-
*/
235-
#ifdefWIN32
236-
staticvoid
237-
shutdown_parallel_dump_utils(intcode,void*unused)
238-
{
239-
/* Call the cleanup function only from the main thread */
240-
if (mainThreadId==GetCurrentThreadId())
241-
WSACleanup();
242-
}
243-
#endif
244-
245232
/*
246233
* Initialize parallel dump support --- should be called early in process
247234
* startup. (Currently, this is called whether or not we intend parallel
@@ -267,8 +254,7 @@ init_parallel_dump_utils(void)
267254
pg_log_error("WSAStartup failed: %d",err);
268255
exit_nicely(1);
269256
}
270-
/* ... and arrange to shut it down at exit */
271-
on_exit_nicely(shutdown_parallel_dump_utils,NULL);
257+
272258
parallel_init_done= true;
273259
}
274260
#endif

‎src/interfaces/libpq/fe-connect.c

Lines changed: 17 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -3866,23 +3866,30 @@ makeEmptyPGconn(void)
38663866
#ifdefWIN32
38673867

38683868
/*
3869-
* Make sure socket support is up and running.
3869+
* Make sure socket support is up and running in this process.
3870+
*
3871+
* Note: the Windows documentation says that we should eventually do a
3872+
* matching WSACleanup() call, but experience suggests that that is at
3873+
* least as likely to cause problems as fix them. So we don't.
38703874
*/
3871-
WSADATAwsaData;
3875+
staticboolwsastartup_done= false;
38723876

3873-
if (WSAStartup(MAKEWORD(1,1),&wsaData))
3874-
returnNULL;
3877+
if (!wsastartup_done)
3878+
{
3879+
WSADATAwsaData;
3880+
3881+
if (WSAStartup(MAKEWORD(1,1),&wsaData)!=0)
3882+
returnNULL;
3883+
wsastartup_done= true;
3884+
}
3885+
3886+
/* Forget any earlier error */
38753887
WSASetLastError(0);
3876-
#endif
3888+
#endif/* WIN32 */
38773889

38783890
conn= (PGconn*)malloc(sizeof(PGconn));
38793891
if (conn==NULL)
3880-
{
3881-
#ifdefWIN32
3882-
WSACleanup();
3883-
#endif
38843892
returnconn;
3885-
}
38863893

38873894
/* Zero all pointers and booleans */
38883895
MemSet(conn,0,sizeof(PGconn));
@@ -4075,10 +4082,6 @@ freePGconn(PGconn *conn)
40754082
termPQExpBuffer(&conn->workBuffer);
40764083

40774084
free(conn);
4078-
4079-
#ifdefWIN32
4080-
WSACleanup();
4081-
#endif
40824085
}
40834086

40844087
/*

0 commit comments

Comments
 (0)

[8]ページ先頭

©2009-2025 Movatter.jp