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injection_points: Add initialization of shmem state when loading module

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This commits adds callbacks to initialize the shared memory state of the
module when loaded with shared_preload_libraries.  This is necessary to
be able to update the test introduced in 768a9fd5535f to use the macros
INJECTION_POINT_{LOAD,CACHED}() rather than a SQL function in the module
injection_points forcing a load, as this test runs a callback in a
critical section where no memory allocation should happen.

Initializing the shared memory state of the module while loading
provides a strict control on the timing of its allocation.  If the
module is not loaded at startup, it will use a GetNamedDSMSegment()
instead to initialize its shmem state on-the-fly.

Per discussion with Álvaro Herrera.

Author: Michael Paquier
Discussion: https://postgr.es/m/ZsUnJUlSOBNAzwW1@paquier.xyz
This commit is contained in:
Michael Paquier 2024-08-23 10:12:58 +09:00
parent edcb712585
commit b2b023aa37
1 changed files with 59 additions and 3 deletions
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62
src/test/modules/injection_points/injection_points.c
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@ -68,7 +68,12 @@ typedef struct InjectionPointCondition
*/
static List *inj_list_local = NIL;
/* Shared state information for injection points. */
/*
* Shared state information for injection points.
*
* This state data can be initialized in two ways: dynamically with a DSM
* or when loading the module.
*/
typedef struct InjectionPointSharedState
{
/* Protects access to other fields */
@ -97,8 +102,13 @@ extern PGDLLEXPORT void injection_wait(const char *name,
/* track if injection points attached in this process are linked to it */
static bool injection_point_local = false;
/* Shared memory init callbacks */
static shmem_request_hook_type prev_shmem_request_hook = NULL;
static shmem_startup_hook_type prev_shmem_startup_hook = NULL;
/*
* Callback for shared memory area initialization.
* Routine for shared memory area initialization, used as a callback
* when initializing dynamically with a DSM or when loading the module.
*/
static void
injection_point_init_state(void *ptr)
@ -111,8 +121,48 @@ injection_point_init_state(void *ptr)
ConditionVariableInit(&state->wait_point);
}
/* Shared memory initialization when loading module */
static void
injection_shmem_request(void)
{
Size size;
if (prev_shmem_request_hook)
prev_shmem_request_hook();
size = MAXALIGN(sizeof(InjectionPointSharedState));
RequestAddinShmemSpace(size);
}
static void
injection_shmem_startup(void)
{
bool found;
if (prev_shmem_startup_hook)
prev_shmem_startup_hook();
/* Create or attach to the shared memory state */
LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
inj_state = ShmemInitStruct("injection_points",
sizeof(InjectionPointSharedState),
&found);
if (!found)
{
/*
* Initialize shared memory area for this module.
* First time through, so initialize. This is shared with the dynamic
* initialization using a DSM.
*/
injection_point_init_state(inj_state);
}
LWLockRelease(AddinShmemInitLock);
}
/*
* Initialize shared memory area for this module through DSM.
*/
static void
injection_init_shmem(void)
@ -463,6 +513,12 @@ _PG_init(void)
if (!process_shared_preload_libraries_in_progress)
return;
/* Shared memory initialization */
prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = injection_shmem_request;
prev_shmem_startup_hook = shmem_startup_hook;
shmem_startup_hook = injection_shmem_startup;
pgstat_register_inj();
pgstat_register_inj_fixed();
}