Andrew Dunstan wrote:
> Heikki Linnakangas wrote:
>> I'm going to see what happens if I remove all the #ifdef WIN32 blocks in
>> syslogger, and let it use pgpipe() and select() instead of the extra
>> thread.
>
> Sounds reasonable. Let's see how big the changes are on HEAD. I'm not
> sure it's worth creating a different smaller fix for the back branches.
I tried that, and got a crash somewhere in the code that inherits the
syslogger pipe/socket to the child process. I don't understand why, and
I don't feel like debugging any deeper into that right now. If you or
someone else wants to give it a shot, that would be good. If not, I
might try again some other day after sleeping over it.
Anyway, here's the patch I had in mind for back-branches.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 22cf5f2..ee449ac 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -117,7 +117,7 @@ HANDLE syslogPipe[2] = {0, 0};
#ifdef WIN32
static HANDLE threadHandle = 0;
-static CRITICAL_SECTION sysfileSection;
+static CRITICAL_SECTION sysloggerSection;
#endif
/*
@@ -268,7 +268,8 @@ SysLoggerMain(int argc, char *argv[])
#ifdef WIN32
/* Fire up separate data transfer thread */
- InitializeCriticalSection(&sysfileSection);
+ InitializeCriticalSection(&sysloggerSection);
+ EnterCriticalSection(&sysloggerSection);
threadHandle = (HANDLE) _beginthreadex(NULL, 0, pipeThread, NULL, 0, NULL);
if (threadHandle == 0)
@@ -423,8 +424,16 @@ SysLoggerMain(int argc, char *argv[])
* 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
* 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);
+
+ EnterCriticalSection(&sysloggerSection);
#endif /* WIN32 */
if (pipe_eof_seen)
@@ -911,17 +920,9 @@ write_syslogger_file(const char *buffer, int count, int destination)
if (destination == LOG_DESTINATION_CSVLOG && csvlogFile == NULL)
open_csvlogfile();
-#ifdef WIN32
- EnterCriticalSection(&sysfileSection);
-#endif
-
logfile = destination == LOG_DESTINATION_CSVLOG ? csvlogFile : syslogFile;
rc = fwrite(buffer, 1, count, logfile);
-#ifdef WIN32
- LeaveCriticalSection(&sysfileSection);
-#endif
-
/* can't use ereport here because of possible recursion */
if (rc != count)
write_stderr("could not write to log file: %s\n", strerror(errno));
@@ -945,11 +946,21 @@ pipeThread(void *arg)
for (;;)
{
DWORD bytesRead;
+ BOOL result;
+
+ result = ReadFile(syslogPipe[0],
+ logbuffer + bytes_in_logbuffer,
+ sizeof(logbuffer) - bytes_in_logbuffer,
+ &bytesRead, 0);
- if (!ReadFile(syslogPipe[0],
- logbuffer + bytes_in_logbuffer,
- sizeof(logbuffer) - bytes_in_logbuffer,
- &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();
@@ -966,6 +977,7 @@ pipeThread(void *arg)
bytes_in_logbuffer += bytesRead;
process_pipe_input(logbuffer, &bytes_in_logbuffer);
}
+ LeaveCriticalSection(&sysloggerSection);
}
/* We exit the above loop only upon detecting pipe EOF */
@@ -974,6 +986,7 @@ pipeThread(void *arg)
/* if there's any data left then force it out now */
flush_pipe_input(logbuffer, &bytes_in_logbuffer);
+ LeaveCriticalSection(&sysloggerSection);
_endthread();
return 0;
}
@@ -1097,18 +1110,9 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
_setmode(_fileno(fh), _O_TEXT); /* use CRLF line endings on Windows */
#endif
- /* On Windows, need to interlock against data-transfer thread */
-#ifdef WIN32
- EnterCriticalSection(&sysfileSection);
-#endif
-
fclose(syslogFile);
syslogFile = fh;
-#ifdef WIN32
- LeaveCriticalSection(&sysfileSection);
-#endif
-
/* instead of pfree'ing filename, remember it for next time */
if (last_file_name != NULL)
pfree(last_file_name);
@@ -1164,18 +1168,9 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
_setmode(_fileno(fh), _O_TEXT); /* use CRLF line endings on Windows */
#endif
- /* On Windows, need to interlock against data-transfer thread */
-#ifdef WIN32
- EnterCriticalSection(&sysfileSection);
-#endif
-
fclose(csvlogFile);
csvlogFile = fh;
-#ifdef WIN32
- LeaveCriticalSection(&sysfileSection);
-#endif
-
/* instead of pfree'ing filename, remember it for next time */
if (last_csv_file_name != NULL)
pfree(last_csv_file_name);
--
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