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Commit249a899

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Install an atexit(2) callback that ensures that proc_exit's cleanup processing
will still be performed if something in a backend process calls exit()directly, instead of going through proc_exit() as we prefer. This is a secondresponse to the issue that we might load third-party code that doesn't know itshould not call exit(). Such a call will now cause a reasonably gracefulbackend shutdown, if possible. (Of course, if the reason for the exit() callis out-of-memory or some such, we might not be able to recover, but at leastwe will try.)
1 parent969d7cd commit249a899

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1 file changed

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  • src/backend/storage/ipc

1 file changed

+123
-40
lines changed

‎src/backend/storage/ipc/ipc.c

Lines changed: 123 additions & 40 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
*
1515
* IDENTIFICATION
16-
* $PostgreSQL: pgsql/src/backend/storage/ipc/ipc.c,v 1.102 2009/01/01 17:23:47 momjian Exp $
16+
* $PostgreSQL: pgsql/src/backend/storage/ipc/ipc.c,v 1.103 2009/05/05 20:06:07 tgl Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
@@ -37,6 +37,15 @@
3737
*/
3838
boolproc_exit_inprogress= false;
3939

40+
/*
41+
* This flag tracks whether we've called atexit(2) in the current process
42+
* (or in the parent postmaster).
43+
*/
44+
staticboolatexit_callback_setup= false;
45+
46+
/* local functions */
47+
staticvoidproc_exit_prepare(intcode);
48+
4049

4150
/* ----------------------------------------------------------------
4251
*exit() handling stuff
@@ -69,51 +78,21 @@ static inton_proc_exit_index,
6978
*
7079
*this function calls all the callbacks registered
7180
*for it (to free resources) and then calls exit.
81+
*
7282
*This should be the only function to call exit().
7383
*-cim 2/6/90
84+
*
85+
*Unfortunately, we can't really guarantee that add-on code
86+
*obeys the rule of not calling exit() directly. So, while
87+
*this is the preferred way out of the system, we also register
88+
*an atexit callback that will make sure cleanup happens.
7489
* ----------------------------------------------------------------
7590
*/
7691
void
7792
proc_exit(intcode)
7893
{
79-
/*
80-
* Once we set this flag, we are committed to exit. Any ereport() will
81-
* NOT send control back to the main loop, but right back here.
82-
*/
83-
proc_exit_inprogress= true;
84-
85-
/*
86-
* Forget any pending cancel or die requests; we're doing our best to
87-
* close up shop already. Note that the signal handlers will not set
88-
* these flags again, now that proc_exit_inprogress is set.
89-
*/
90-
InterruptPending= false;
91-
ProcDiePending= false;
92-
QueryCancelPending= false;
93-
/* And let's just make *sure* we're not interrupted ... */
94-
ImmediateInterruptOK= false;
95-
InterruptHoldoffCount=1;
96-
CritSectionCount=0;
97-
98-
elog(DEBUG3,"proc_exit(%d)",code);
99-
100-
/* do our shared memory exits first */
101-
shmem_exit(code);
102-
103-
/*
104-
* call all the callbacks registered before calling exit().
105-
*
106-
* Note that since we decrement on_proc_exit_index each time, if a
107-
* callback calls ereport(ERROR) or ereport(FATAL) then it won't be
108-
* invoked again when control comes back here (nor will the
109-
* previously-completed callbacks). So, an infinite loop should not be
110-
* possible.
111-
*/
112-
while (--on_proc_exit_index >=0)
113-
(*on_proc_exit_list[on_proc_exit_index].function) (code,
114-
on_proc_exit_list[on_proc_exit_index].arg);
115-
116-
elog(DEBUG3,"exit(%d)",code);
94+
/* Clean up everything that must be cleaned up */
95+
proc_exit_prepare(code);
11796

11897
#ifdefPROFILE_PID_DIR
11998
{
@@ -134,7 +113,10 @@ proc_exit(int code)
134113
*
135114
* Note that we do this here instead of in an on_proc_exit() callback
136115
* because we want to ensure that this code executes last - we don't
137-
* want to interfere with any other on_proc_exit() callback.
116+
* want to interfere with any other on_proc_exit() callback. For
117+
* the same reason, we do not include it in proc_exit_prepare ...
118+
* so if you are exiting in the "wrong way" you won't drop your profile
119+
* in a nice place.
138120
*/
139121
chargprofDirName[32];
140122

@@ -149,9 +131,59 @@ proc_exit(int code)
149131
}
150132
#endif
151133

134+
elog(DEBUG3,"exit(%d)",code);
135+
152136
exit(code);
153137
}
154138

139+
/*
140+
* Code shared between proc_exit and the atexit handler. Note that in
141+
* normal exit through proc_exit, this will actually be called twice ...
142+
* but the second call will have nothing to do.
143+
*/
144+
staticvoid
145+
proc_exit_prepare(intcode)
146+
{
147+
/*
148+
* Once we set this flag, we are committed to exit. Any ereport() will
149+
* NOT send control back to the main loop, but right back here.
150+
*/
151+
proc_exit_inprogress= true;
152+
153+
/*
154+
* Forget any pending cancel or die requests; we're doing our best to
155+
* close up shop already. Note that the signal handlers will not set
156+
* these flags again, now that proc_exit_inprogress is set.
157+
*/
158+
InterruptPending= false;
159+
ProcDiePending= false;
160+
QueryCancelPending= false;
161+
/* And let's just make *sure* we're not interrupted ... */
162+
ImmediateInterruptOK= false;
163+
InterruptHoldoffCount=1;
164+
CritSectionCount=0;
165+
166+
/* do our shared memory exits first */
167+
shmem_exit(code);
168+
169+
elog(DEBUG3,"proc_exit(%d)",code);
170+
171+
/*
172+
* call all the registered callbacks.
173+
*
174+
* Note that since we decrement on_proc_exit_index each time, if a
175+
* callback calls ereport(ERROR) or ereport(FATAL) then it won't be
176+
* invoked again when control comes back here (nor will the
177+
* previously-completed callbacks). So, an infinite loop should not be
178+
* possible.
179+
*/
180+
while (--on_proc_exit_index >=0)
181+
(*on_proc_exit_list[on_proc_exit_index].function) (code,
182+
on_proc_exit_list[on_proc_exit_index].arg);
183+
184+
on_proc_exit_index=0;
185+
}
186+
155187
/* ------------------
156188
* Run all of the on_shmem_exit routines --- but don't actually exit.
157189
* This is used by the postmaster to re-initialize shared memory and
@@ -176,6 +208,37 @@ shmem_exit(int code)
176208
on_shmem_exit_index=0;
177209
}
178210

211+
/* ----------------------------------------------------------------
212+
*atexit_callback
213+
*
214+
*Backstop to ensure that direct calls of exit() don't mess us up.
215+
*
216+
* Somebody who was being really uncooperative could call _exit(),
217+
* but for that case we have a "dead man switch" that will make the
218+
* postmaster treat it as a crash --- see pmsignal.c.
219+
* ----------------------------------------------------------------
220+
*/
221+
#ifdefHAVE_ATEXIT
222+
223+
staticvoid
224+
atexit_callback(void)
225+
{
226+
/* Clean up everything that must be cleaned up */
227+
/* ... too bad we don't know the real exit code ... */
228+
proc_exit_prepare(-1);
229+
}
230+
231+
#else/* assume we have on_exit instead */
232+
233+
staticvoid
234+
atexit_callback(intexitstatus,void*arg)
235+
{
236+
/* Clean up everything that must be cleaned up */
237+
proc_exit_prepare(exitstatus);
238+
}
239+
240+
#endif/* HAVE_ATEXIT */
241+
179242
/* ----------------------------------------------------------------
180243
*on_proc_exit
181244
*
@@ -195,6 +258,16 @@ on_proc_exit(pg_on_exit_callback function, Datum arg)
195258
on_proc_exit_list[on_proc_exit_index].arg=arg;
196259

197260
++on_proc_exit_index;
261+
262+
if (!atexit_callback_setup)
263+
{
264+
#ifdefHAVE_ATEXIT
265+
atexit(atexit_callback);
266+
#else
267+
on_exit(atexit_callback,NULL);
268+
#endif
269+
atexit_callback_setup= true;
270+
}
198271
}
199272

200273
/* ----------------------------------------------------------------
@@ -216,6 +289,16 @@ on_shmem_exit(pg_on_exit_callback function, Datum arg)
216289
on_shmem_exit_list[on_shmem_exit_index].arg=arg;
217290

218291
++on_shmem_exit_index;
292+
293+
if (!atexit_callback_setup)
294+
{
295+
#ifdefHAVE_ATEXIT
296+
atexit(atexit_callback);
297+
#else
298+
on_exit(atexit_callback,NULL);
299+
#endif
300+
atexit_callback_setup= true;
301+
}
219302
}
220303

221304
/* ----------------------------------------------------------------

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