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Commit961ad3f

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On Windows, syslogger runs in two threads. The main thread processes config
reload and rotation signals, and a helper thread reads messages from thepipe and writes them to the log file. However, server code isn't generallythread-safe, so if both try to do e.g palloc()/pfree() at the same time,bad things will happen. To fix that, use a critical section (which is likea mutex) to enforce that only one the threads are active at a time.
1 parent78974cf commit961ad3f

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1 file changed

+28
-33
lines changed

1 file changed

+28
-33
lines changed

‎src/backend/postmaster/syslogger.c

Lines changed: 28 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@
1818
*
1919
*
2020
* IDENTIFICATION
21-
* $PostgreSQL: pgsql/src/backend/postmaster/syslogger.c,v 1.56 2010/04/01 20:12:22 heikki Exp $
21+
* $PostgreSQL: pgsql/src/backend/postmaster/syslogger.c,v 1.57 2010/04/16 09:51:49 heikki Exp $
2222
*
2323
*-------------------------------------------------------------------------
2424
*/
@@ -117,7 +117,7 @@ HANDLEsyslogPipe[2] = {0, 0};
117117

118118
#ifdefWIN32
119119
staticHANDLEthreadHandle=0;
120-
staticCRITICAL_SECTIONsysfileSection;
120+
staticCRITICAL_SECTIONsysloggerSection;
121121
#endif
122122

123123
/*
@@ -268,7 +268,8 @@ SysLoggerMain(int argc, char *argv[])
268268

269269
#ifdefWIN32
270270
/* Fire up separate data transfer thread */
271-
InitializeCriticalSection(&sysfileSection);
271+
InitializeCriticalSection(&sysloggerSection);
272+
EnterCriticalSection(&sysloggerSection);
272273

273274
threadHandle= (HANDLE)_beginthreadex(NULL,0,pipeThread,NULL,0,NULL);
274275
if (threadHandle==0)
@@ -423,8 +424,16 @@ SysLoggerMain(int argc, char *argv[])
423424
* On Windows we leave it to a separate thread to transfer data and
424425
* detect pipe EOF. The main thread just wakes up once a second to
425426
* check for SIGHUP and rotation conditions.
427+
*
428+
* Server code isn't generally thread-safe, so we ensure that only
429+
* one of the threads is active at a time by entering the critical
430+
* section whenever we're not sleeping.
426431
*/
432+
LeaveCriticalSection(&sysloggerSection);
433+
427434
pg_usleep(1000000L);
435+
436+
EnterCriticalSection(&sysloggerSection);
428437
#endif/* WIN32 */
429438

430439
if (pipe_eof_seen)
@@ -911,17 +920,9 @@ write_syslogger_file(const char *buffer, int count, int destination)
911920
if (destination==LOG_DESTINATION_CSVLOG&&csvlogFile==NULL)
912921
open_csvlogfile();
913922

914-
#ifdefWIN32
915-
EnterCriticalSection(&sysfileSection);
916-
#endif
917-
918923
logfile=destination==LOG_DESTINATION_CSVLOG ?csvlogFile :syslogFile;
919924
rc=fwrite(buffer,1,count,logfile);
920925

921-
#ifdefWIN32
922-
LeaveCriticalSection(&sysfileSection);
923-
#endif
924-
925926
/* can't use ereport here because of possible recursion */
926927
if (rc!=count)
927928
write_stderr("could not write to log file: %s\n",strerror(errno));
@@ -945,11 +946,21 @@ pipeThread(void *arg)
945946
for (;;)
946947
{
947948
DWORDbytesRead;
949+
BOOLresult;
950+
951+
result=ReadFile(syslogPipe[0],
952+
logbuffer+bytes_in_logbuffer,
953+
sizeof(logbuffer)-bytes_in_logbuffer,
954+
&bytesRead,0);
948955

949-
if (!ReadFile(syslogPipe[0],
950-
logbuffer+bytes_in_logbuffer,
951-
sizeof(logbuffer)-bytes_in_logbuffer,
952-
&bytesRead,0))
956+
/*
957+
* Enter critical section before doing anything that might touch
958+
* global state shared by the main thread. Anything that uses
959+
* palloc()/pfree() in particular are not safe outside the critical
960+
* section.
961+
*/
962+
EnterCriticalSection(&sysloggerSection);
963+
if (!result)
953964
{
954965
DWORDerror=GetLastError();
955966

@@ -966,6 +977,7 @@ pipeThread(void *arg)
966977
bytes_in_logbuffer+=bytesRead;
967978
process_pipe_input(logbuffer,&bytes_in_logbuffer);
968979
}
980+
LeaveCriticalSection(&sysloggerSection);
969981
}
970982

971983
/* We exit the above loop only upon detecting pipe EOF */
@@ -974,6 +986,7 @@ pipeThread(void *arg)
974986
/* if there's any data left then force it out now */
975987
flush_pipe_input(logbuffer,&bytes_in_logbuffer);
976988

989+
LeaveCriticalSection(&sysloggerSection);
977990
_endthread();
978991
return0;
979992
}
@@ -1097,18 +1110,9 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
10971110
_setmode(_fileno(fh),_O_TEXT);/* use CRLF line endings on Windows */
10981111
#endif
10991112

1100-
/* On Windows, need to interlock against data-transfer thread */
1101-
#ifdefWIN32
1102-
EnterCriticalSection(&sysfileSection);
1103-
#endif
1104-
11051113
fclose(syslogFile);
11061114
syslogFile=fh;
11071115

1108-
#ifdefWIN32
1109-
LeaveCriticalSection(&sysfileSection);
1110-
#endif
1111-
11121116
/* instead of pfree'ing filename, remember it for next time */
11131117
if (last_file_name!=NULL)
11141118
pfree(last_file_name);
@@ -1164,18 +1168,9 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
11641168
_setmode(_fileno(fh),_O_TEXT);/* use CRLF line endings on Windows */
11651169
#endif
11661170

1167-
/* On Windows, need to interlock against data-transfer thread */
1168-
#ifdefWIN32
1169-
EnterCriticalSection(&sysfileSection);
1170-
#endif
1171-
11721171
fclose(csvlogFile);
11731172
csvlogFile=fh;
11741173

1175-
#ifdefWIN32
1176-
LeaveCriticalSection(&sysfileSection);
1177-
#endif
1178-
11791174
/* instead of pfree'ing filename, remember it for next time */
11801175
if (last_csv_file_name!=NULL)
11811176
pfree(last_csv_file_name);

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