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Commit33181b4

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Introduce private data area for injection points
This commit extends the backend-side infrastructure of injection pointsso as it becomes possible to register some input data when attaching apoint. This private data can be registered with the function name andthe library name of the callback when attaching a point, then it isgiven as input argument to the callback. This gives the possibility formodules to pass down custom data at runtime when attaching a pointwithout managing that internally, in a manner consistent with thecallback entry retrieved from the hash shmem table storing the injectionpoint data.InjectionPointAttach() gains two arguments, to be able to define theprivate data contents and its size.A follow-up commit will rely on this infrastructure to close a racecondition with the injection point detach in the moduleinjection_points.While on it, this changes InjectionPointDetach() to return a boolean,returning false if a point cannot be detached. This has been mentionedby Noah as useful when it comes to implement more complex tests withconcurrent point detach, solid with the automatic detach done for localpoints in the test module.Documentation is adjusted in consequence.Per discussion with Noah Misch.Reviewed-by: Noah MischDiscussion:https://postgr.es/m/20240509031553.47@rfd.leadboat.com
1 parent407e0b0 commit33181b4

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5 files changed

+74
-28
lines changed

5 files changed

+74
-28
lines changed

‎doc/src/sgml/xfunc.sgml

Lines changed: 10 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -3624,20 +3624,24 @@ INJECTION_POINT(name);
36243624
<programlisting>
36253625
extern void InjectionPointAttach(const char *name,
36263626
const char *library,
3627-
const char *function);
3627+
const char *function,
3628+
const void *private_data,
3629+
int private_data_size);
36283630
</programlisting>
36293631

36303632
<literal>name</literal> is the name of the injection point, which when
36313633
reached during execution will execute the <literal>function</literal>
3632-
loaded from <literal>library</literal>.
3634+
loaded from <literal>library</literal>. <literal>private_data</literal>
3635+
is a private area of data of size <literal>private_data_size</literal>
3636+
given as argument to the callback when executed.
36333637
</para>
36343638

36353639
<para>
36363640
Here is an example of callback for
36373641
<literal>InjectionPointCallback</literal>:
36383642
<programlisting>
36393643
static void
3640-
custom_injection_callback(const char *name)
3644+
custom_injection_callback(const char *name, const void *private_data)
36413645
{
36423646
elog(NOTICE, "%s: executed custom callback", name);
36433647
}
@@ -3650,8 +3654,10 @@ custom_injection_callback(const char *name)
36503654
<para>
36513655
Optionally, it is possible to detach an injection point by calling:
36523656
<programlisting>
3653-
externvoid InjectionPointDetach(const char *name);
3657+
externbool InjectionPointDetach(const char *name);
36543658
</programlisting>
3659+
On success, <literal>true</literal> is returned, <literal>false</literal>
3660+
otherwise.
36553661
</para>
36563662

36573663
<para>

‎src/backend/utils/misc/injection_point.c

Lines changed: 44 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -42,13 +42,20 @@ static HTAB *InjectionPointHash;/* find points from names */
4242
#defineINJ_NAME_MAXLEN64
4343
#defineINJ_LIB_MAXLEN128
4444
#defineINJ_FUNC_MAXLEN128
45+
#defineINJ_PRIVATE_MAXLEN1024
4546

4647
/* Single injection point stored in InjectionPointHash */
4748
typedefstructInjectionPointEntry
4849
{
4950
charname[INJ_NAME_MAXLEN];/* hash key */
5051
charlibrary[INJ_LIB_MAXLEN];/* library */
5152
charfunction[INJ_FUNC_MAXLEN];/* function */
53+
54+
/*
55+
* Opaque data area that modules can use to pass some custom data to
56+
* callbacks, registered when attached.
57+
*/
58+
charprivate_data[INJ_PRIVATE_MAXLEN];
5259
}InjectionPointEntry;
5360

5461
#defineINJECTION_POINT_HASH_INIT_SIZE16
@@ -61,6 +68,7 @@ typedef struct InjectionPointEntry
6168
typedefstructInjectionPointCacheEntry
6269
{
6370
charname[INJ_NAME_MAXLEN];
71+
charprivate_data[INJ_PRIVATE_MAXLEN];
6472
InjectionPointCallbackcallback;
6573
}InjectionPointCacheEntry;
6674

@@ -73,7 +81,8 @@ static HTAB *InjectionPointCache = NULL;
7381
*/
7482
staticvoid
7583
injection_point_cache_add(constchar*name,
76-
InjectionPointCallbackcallback)
84+
InjectionPointCallbackcallback,
85+
constvoid*private_data)
7786
{
7887
InjectionPointCacheEntry*entry;
7988
boolfound;
@@ -99,6 +108,8 @@ injection_point_cache_add(const char *name,
99108
Assert(!found);
100109
strlcpy(entry->name,name,sizeof(entry->name));
101110
entry->callback=callback;
111+
if (private_data!=NULL)
112+
memcpy(entry->private_data,private_data,INJ_PRIVATE_MAXLEN);
102113
}
103114

104115
/*
@@ -124,11 +135,14 @@ injection_point_cache_remove(const char *name)
124135
* Retrieve an injection point from the local cache, if any.
125136
*/
126137
staticInjectionPointCallback
127-
injection_point_cache_get(constchar*name)
138+
injection_point_cache_get(constchar*name,constvoid**private_data)
128139
{
129140
boolfound;
130141
InjectionPointCacheEntry*entry;
131142

143+
if (private_data)
144+
*private_data=NULL;
145+
132146
/* no callback if no cache yet */
133147
if (InjectionPointCache==NULL)
134148
returnNULL;
@@ -137,7 +151,11 @@ injection_point_cache_get(const char *name)
137151
hash_search(InjectionPointCache,name,HASH_FIND,&found);
138152

139153
if (found)
154+
{
155+
if (private_data)
156+
*private_data=entry->private_data;
140157
returnentry->callback;
158+
}
141159

142160
returnNULL;
143161
}
@@ -186,7 +204,9 @@ InjectionPointShmemInit(void)
186204
void
187205
InjectionPointAttach(constchar*name,
188206
constchar*library,
189-
constchar*function)
207+
constchar*function,
208+
constvoid*private_data,
209+
intprivate_data_size)
190210
{
191211
#ifdefUSE_INJECTION_POINTS
192212
InjectionPointEntry*entry_by_name;
@@ -201,6 +221,9 @@ InjectionPointAttach(const char *name,
201221
if (strlen(function) >=INJ_FUNC_MAXLEN)
202222
elog(ERROR,"injection point function %s too long (maximum of %u)",
203223
function,INJ_FUNC_MAXLEN);
224+
if (private_data_size >=INJ_PRIVATE_MAXLEN)
225+
elog(ERROR,"injection point data too long (maximum of %u)",
226+
INJ_PRIVATE_MAXLEN);
204227

205228
/*
206229
* Allocate and register a new injection point. A new point should not
@@ -223,6 +246,8 @@ InjectionPointAttach(const char *name,
223246
entry_by_name->library[INJ_LIB_MAXLEN-1]='\0';
224247
strlcpy(entry_by_name->function,function,sizeof(entry_by_name->function));
225248
entry_by_name->function[INJ_FUNC_MAXLEN-1]='\0';
249+
if (private_data!=NULL)
250+
memcpy(entry_by_name->private_data,private_data,private_data_size);
226251

227252
LWLockRelease(InjectionPointLock);
228253

@@ -233,8 +258,10 @@ InjectionPointAttach(const char *name,
233258

234259
/*
235260
* Detach an existing injection point.
261+
*
262+
* Returns true if the injection point was detached, false otherwise.
236263
*/
237-
void
264+
bool
238265
InjectionPointDetach(constchar*name)
239266
{
240267
#ifdefUSE_INJECTION_POINTS
@@ -245,10 +272,12 @@ InjectionPointDetach(const char *name)
245272
LWLockRelease(InjectionPointLock);
246273

247274
if (!found)
248-
elog(ERROR,"injection point \"%s\" not found",name);
275+
return false;
249276

277+
return true;
250278
#else
251279
elog(ERROR,"Injection points are not supported by this build");
280+
return true;/* silence compiler */
252281
#endif
253282
}
254283

@@ -265,6 +294,7 @@ InjectionPointRun(const char *name)
265294
InjectionPointEntry*entry_by_name;
266295
boolfound;
267296
InjectionPointCallbackinjection_callback;
297+
constvoid*private_data;
268298

269299
LWLockAcquire(InjectionPointLock,LW_SHARED);
270300
entry_by_name= (InjectionPointEntry*)
@@ -286,10 +316,10 @@ InjectionPointRun(const char *name)
286316
* Check if the callback exists in the local cache, to avoid unnecessary
287317
* external loads.
288318
*/
289-
injection_callback=injection_point_cache_get(name);
290-
if (injection_callback==NULL)
319+
if (injection_point_cache_get(name,NULL)==NULL)
291320
{
292321
charpath[MAXPGPATH];
322+
InjectionPointCallbackinjection_callback_local;
293323

294324
/* not found in local cache, so load and register */
295325
snprintf(path,MAXPGPATH,"%s/%s%s",pkglib_path,
@@ -299,18 +329,21 @@ InjectionPointRun(const char *name)
299329
elog(ERROR,"could not find library \"%s\" for injection point \"%s\"",
300330
path,name);
301331

302-
injection_callback= (InjectionPointCallback)
332+
injection_callback_local= (InjectionPointCallback)
303333
load_external_function(path,entry_by_name->function, false,NULL);
304334

305-
if (injection_callback==NULL)
335+
if (injection_callback_local==NULL)
306336
elog(ERROR,"could not find function \"%s\" in library \"%s\" for injection point \"%s\"",
307337
entry_by_name->function,path,name);
308338

309339
/* add it to the local cache when found */
310-
injection_point_cache_add(name,injection_callback);
340+
injection_point_cache_add(name,injection_callback_local,
341+
entry_by_name->private_data);
311342
}
312343

313-
injection_callback(name);
344+
/* Now loaded, so get it. */
345+
injection_callback=injection_point_cache_get(name,&private_data);
346+
injection_callback(name,private_data);
314347
#else
315348
elog(ERROR,"Injection points are not supported by this build");
316349
#endif

‎src/include/utils/injection_point.h

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -23,15 +23,18 @@
2323
/*
2424
* Typedef for callback function launched by an injection point.
2525
*/
26-
typedefvoid (*InjectionPointCallback) (constchar*name);
26+
typedefvoid (*InjectionPointCallback) (constchar*name,
27+
constvoid*private_data);
2728

2829
externSizeInjectionPointShmemSize(void);
2930
externvoidInjectionPointShmemInit(void);
3031

3132
externvoidInjectionPointAttach(constchar*name,
3233
constchar*library,
33-
constchar*function);
34+
constchar*function,
35+
constvoid*private_data,
36+
intprivate_data_size);
3437
externvoidInjectionPointRun(constchar*name);
35-
externvoidInjectionPointDetach(constchar*name);
38+
externboolInjectionPointDetach(constchar*name);
3639

3740
#endif/* INJECTION_POINT_H */

‎src/test/modules/injection_points/expected/injection_points.out

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -114,7 +114,7 @@ NOTICE: notice triggered for injection point TestInjectionLog2
114114
(1 row)
115115

116116
SELECT injection_points_detach('TestInjectionLog'); -- fails
117-
ERROR: injection point "TestInjectionLog" not found
117+
ERROR:could not detachinjection point "TestInjectionLog"
118118
SELECT injection_points_run('TestInjectionLog2'); -- notice
119119
NOTICE: notice triggered for injection point TestInjectionLog2
120120
injection_points_run

‎src/test/modules/injection_points/injection_points.c

Lines changed: 13 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -73,9 +73,12 @@ typedef struct InjectionPointSharedState
7373
/* Pointer to shared-memory state. */
7474
staticInjectionPointSharedState*inj_state=NULL;
7575

76-
externPGDLLEXPORTvoidinjection_error(constchar*name);
77-
externPGDLLEXPORTvoidinjection_notice(constchar*name);
78-
externPGDLLEXPORTvoidinjection_wait(constchar*name);
76+
externPGDLLEXPORTvoidinjection_error(constchar*name,
77+
constvoid*private_data);
78+
externPGDLLEXPORTvoidinjection_notice(constchar*name,
79+
constvoid*private_data);
80+
externPGDLLEXPORTvoidinjection_wait(constchar*name,
81+
constvoid*private_data);
7982

8083
/* track if injection points attached in this process are linked to it */
8184
staticboolinjection_point_local= false;
@@ -189,7 +192,7 @@ injection_points_cleanup(int code, Datum arg)
189192

190193
/* Detach, without holding the spinlock */
191194
for (inti=0;i<count;i++)
192-
InjectionPointDetach(names[i]);
195+
(void)InjectionPointDetach(names[i]);
193196

194197
/* Clear all the conditions */
195198
SpinLockAcquire(&inj_state->lock);
@@ -211,7 +214,7 @@ injection_points_cleanup(int code, Datum arg)
211214

212215
/* Set of callbacks available to be attached to an injection point. */
213216
void
214-
injection_error(constchar*name)
217+
injection_error(constchar*name,constvoid*private_data)
215218
{
216219
if (!injection_point_allowed(name))
217220
return;
@@ -220,7 +223,7 @@ injection_error(const char *name)
220223
}
221224

222225
void
223-
injection_notice(constchar*name)
226+
injection_notice(constchar*name,constvoid*private_data)
224227
{
225228
if (!injection_point_allowed(name))
226229
return;
@@ -230,7 +233,7 @@ injection_notice(const char *name)
230233

231234
/* Wait on a condition variable, awaken by injection_points_wakeup() */
232235
void
233-
injection_wait(constchar*name)
236+
injection_wait(constchar*name,constvoid*private_data)
234237
{
235238
uint32old_wait_counts=0;
236239
intindex=-1;
@@ -311,7 +314,7 @@ injection_points_attach(PG_FUNCTION_ARGS)
311314
else
312315
elog(ERROR,"incorrect action \"%s\" for injection point creation",action);
313316

314-
InjectionPointAttach(name,"injection_points",function);
317+
InjectionPointAttach(name,"injection_points",function,NULL,0);
315318

316319
if (injection_point_local)
317320
{
@@ -430,7 +433,8 @@ injection_points_detach(PG_FUNCTION_ARGS)
430433
{
431434
char*name=text_to_cstring(PG_GETARG_TEXT_PP(0));
432435

433-
InjectionPointDetach(name);
436+
if (!InjectionPointDetach(name))
437+
elog(ERROR,"could not detach injection point \"%s\"",name);
434438

435439
if (inj_state==NULL)
436440
injection_init_shmem();

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