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On Windows, syslogger runs in two threads. The main thread processes config

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reload and rotation signals, and a helper thread reads messages from the
pipe and writes them to the log file. However, server code isn't generally
thread-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 like
a mutex) to enforce that only one the threads are active at a time.
This commit is contained in:
Heikki Linnakangas 2010-04-16 09:52:15 +00:00
parent 06464ef972
commit 345c2c5e76
1 changed files with 28 additions and 20 deletions
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48
src/backend/postmaster/syslogger.c
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@ -18,7 +18,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/postmaster/syslogger.c,v 1.29.2.5 2010/04/01 20:12:42 heikki Exp $ * $PostgreSQL: pgsql/src/backend/postmaster/syslogger.c,v 1.29.2.6 2010/04/16 09:52:15 heikki Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -115,7 +115,7 @@ HANDLE syslogPipe[2] = {0, 0};
#ifdef WIN32 #ifdef WIN32
static HANDLE threadHandle = 0; static HANDLE threadHandle = 0;
static CRITICAL_SECTION sysfileSection; static CRITICAL_SECTION sysloggerSection;
#endif #endif
static void process_pipe_input(char *logbuffer, int *bytes_in_logbuffer); static void process_pipe_input(char *logbuffer, int *bytes_in_logbuffer);
static void flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer); static void flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer);
@ -263,7 +263,8 @@ SysLoggerMain(int argc, char *argv[])
#ifdef WIN32 #ifdef WIN32
/* Fire up separate data transfer thread */ /* Fire up separate data transfer thread */
InitializeCriticalSection(&sysfileSection); InitializeCriticalSection(&sysloggerSection);
EnterCriticalSection(&sysloggerSection);
{ {
unsigned int tid; unsigned int tid;
@ -401,8 +402,16 @@ SysLoggerMain(int argc, char *argv[])
* On Windows we leave it to a separate thread to transfer data and * On Windows we leave it to a separate thread to transfer data and
* detect pipe EOF. The main thread just wakes up once a second to * detect pipe EOF. The main thread just wakes up once a second to
* check for SIGHUP and rotation conditions. * check for SIGHUP and rotation conditions.
*
* Server code isn't generally thread-safe, so we ensure that only
* one of the threads is active at a time by entering the critical
* section whenever we're not sleeping.
*/ */
LeaveCriticalSection(&sysloggerSection);
pg_usleep(1000000L); pg_usleep(1000000L);
EnterCriticalSection(&sysloggerSection);
#endif /* WIN32 */ #endif /* WIN32 */
if (pipe_eof_seen) if (pipe_eof_seen)
@ -913,13 +922,7 @@ write_syslogger_file_binary(const char *buffer, int count)
{ {
int rc; int rc;
#ifndef WIN32
rc = fwrite(buffer, 1, count, syslogFile); rc = fwrite(buffer, 1, count, syslogFile);
#else
EnterCriticalSection(&sysfileSection);
rc = fwrite(buffer, 1, count, syslogFile);
LeaveCriticalSection(&sysfileSection);
#endif
/* can't use ereport here because of possible recursion */ /* can't use ereport here because of possible recursion */
if (rc != count) if (rc != count)
@ -944,11 +947,21 @@ pipeThread(void *arg)
for (;;) for (;;)
{ {
DWORD bytesRead; DWORD bytesRead;
BOOL result;
if (!ReadFile(syslogPipe[0], result = ReadFile(syslogPipe[0],
logbuffer + bytes_in_logbuffer, logbuffer + bytes_in_logbuffer,
sizeof(logbuffer) - bytes_in_logbuffer, sizeof(logbuffer) - bytes_in_logbuffer,
&bytesRead, 0)) &bytesRead, 0);
/*
* Enter critical section before doing anything that might touch
* global state shared by the main thread. Anything that uses
* palloc()/pfree() in particular are not safe outside the critical
* section.
*/
EnterCriticalSection(&sysloggerSection);
if (!result)
{ {
DWORD error = GetLastError(); DWORD error = GetLastError();
@ -965,6 +978,7 @@ pipeThread(void *arg)
bytes_in_logbuffer += bytesRead; bytes_in_logbuffer += bytesRead;
process_pipe_input(logbuffer, &bytes_in_logbuffer); process_pipe_input(logbuffer, &bytes_in_logbuffer);
} }
LeaveCriticalSection(&sysloggerSection);
} }
/* We exit the above loop only upon detecting pipe EOF */ /* We exit the above loop only upon detecting pipe EOF */
@ -973,6 +987,7 @@ pipeThread(void *arg)
/* if there's any data left then force it out now */ /* if there's any data left then force it out now */
flush_pipe_input(logbuffer, &bytes_in_logbuffer); flush_pipe_input(logbuffer, &bytes_in_logbuffer);
LeaveCriticalSection(&sysloggerSection);
_endthread(); _endthread();
return 0; return 0;
} }
@ -1049,15 +1064,8 @@ logfile_rotate(bool time_based_rotation)
_setmode(_fileno(fh), _O_TEXT); /* use CRLF line endings on Windows */ _setmode(_fileno(fh), _O_TEXT); /* use CRLF line endings on Windows */
#endif #endif
/* On Windows, need to interlock against data-transfer thread */
#ifdef WIN32
EnterCriticalSection(&sysfileSection);
#endif
fclose(syslogFile); fclose(syslogFile);
syslogFile = fh; syslogFile = fh;
#ifdef WIN32
LeaveCriticalSection(&sysfileSection);
#endif
set_next_rotation_time(); set_next_rotation_time();