injection_points.c

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/*--------------------------------------------------------------------------
 *
 * injection_points.c
 *      Code for testing injection points.
 *
 * Injection points are able to trigger user-defined callbacks in pre-defined
 * code paths.
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *      src/test/modules/injection_points/injection_points.c
 *
 * -------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "fmgr.h"
#include "injection_stats.h"
#include "miscadmin.h"
#include "nodes/pg_list.h"
#include "nodes/value.h"
#include "storage/condition_variable.h"
#include "storage/dsm_registry.h"
#include "storage/ipc.h"
#include "storage/lwlock.h"
#include "storage/shmem.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/injection_point.h"
#include "utils/memutils.h"
#include "utils/wait_event.h"
 
PG_MODULE_MAGIC;
 
/* Maximum number of waits usable in injection points at once */
#define INJ_MAX_WAIT    8
#define INJ_NAME_MAXLEN 64
 
/*
 * Conditions related to injection points.  This tracks in shared memory the
 * runtime conditions under which an injection point is allowed to run,
 * stored as private_data when an injection point is attached, and passed as
 * argument to the callback.
 *
 * If more types of runtime conditions need to be tracked, this structure
 * should be expanded.
 */
typedef enum InjectionPointConditionType
{
    INJ_CONDITION_ALWAYS = 0,   /* always run */
    INJ_CONDITION_PID,          /* PID restriction */
} InjectionPointConditionType;
 
typedef struct InjectionPointCondition
{
    /* Type of the condition */
    InjectionPointConditionType type;
 
    /* ID of the process where the injection point is allowed to run */
    int         pid;
} InjectionPointCondition;
 
/*
 * List of injection points stored in TopMemoryContext attached
 * locally to this process.
 */
static List *inj_list_local = NIL;
 
/*
 * 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 */
    slock_t     lock;
 
    /* Counters advancing when injection_points_wakeup() is called */
    uint32      wait_counts[INJ_MAX_WAIT];
 
    /* Names of injection points attached to wait counters */
    char        name[INJ_MAX_WAIT][INJ_NAME_MAXLEN];
 
    /* Condition variable used for waits and wakeups */
    ConditionVariable wait_point;
} InjectionPointSharedState;
 
/* Pointer to shared-memory state. */
static InjectionPointSharedState *inj_state = NULL;
 
extern PGDLLEXPORT void injection_error(const char *name,
                                        const void *private_data);
extern PGDLLEXPORT void injection_notice(const char *name,
                                         const void *private_data);
extern PGDLLEXPORT void injection_wait(const char *name,
                                       const void *private_data);
 
/* track if injection points attached in this process are linked to it */
static bool injection_point_local = false;
 
/*
 * GUC variable
 *
 * This GUC is useful to control if statistics should be enabled or not
 * during a test with injection points, like for example if a test relies
 * on a callback run in a critical section where no allocation should happen.
 */
bool        inj_stats_enabled = 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;
 
/*
 * 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)
{
    InjectionPointSharedState *state = (InjectionPointSharedState *) ptr;
 
    SpinLockInit(&state->lock);
    memset(state->wait_counts, 0, sizeof(state->wait_counts));
    memset(state->name, 0, sizeof(state->name));
    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)
    {
        /*
         * 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)
{
    bool        found;
 
    if (inj_state != NULL)
        return;
 
    inj_state = GetNamedDSMSegment("injection_points",
                                   sizeof(InjectionPointSharedState),
                                   injection_point_init_state,
                                   &found);
}
 
/*
 * Check runtime conditions associated to an injection point.
 *
 * Returns true if the named injection point is allowed to run, and false
 * otherwise.
 */
static bool
injection_point_allowed(InjectionPointCondition *condition)
{
    bool        result = true;
 
    switch (condition->type)
    {
        case INJ_CONDITION_PID:
            if (MyProcPid != condition->pid)
                result = false;
            break;
        case INJ_CONDITION_ALWAYS:
            break;
    }
 
    return result;
}
 
/*
 * before_shmem_exit callback to remove injection points linked to a
 * specific process.
 */
static void
injection_points_cleanup(int code, Datum arg)
{
    ListCell   *lc;
 
    /* Leave if nothing is tracked locally */
    if (!injection_point_local)
        return;
 
    /* Detach all the local points */
    foreach(lc, inj_list_local)
    {
        char       *name = strVal(lfirst(lc));
 
        (void) InjectionPointDetach(name);
 
        /* Remove stats entry */
        pgstat_drop_inj(name);
    }
}
 
/* Set of callbacks available to be attached to an injection point. */
void
injection_error(const char *name, const void *private_data)
{
    InjectionPointCondition *condition = (InjectionPointCondition *) private_data;
 
    if (!injection_point_allowed(condition))
        return;
 
    pgstat_report_inj(name);
 
    elog(ERROR, "error triggered for injection point %s", name);
}
 
void
injection_notice(const char *name, const void *private_data)
{
    InjectionPointCondition *condition = (InjectionPointCondition *) private_data;
 
    if (!injection_point_allowed(condition))
        return;
 
    pgstat_report_inj(name);
 
    elog(NOTICE, "notice triggered for injection point %s", name);
}
 
/* Wait on a condition variable, awaken by injection_points_wakeup() */
void
injection_wait(const char *name, const void *private_data)
{
    uint32      old_wait_counts = 0;
    int         index = -1;
    uint32      injection_wait_event = 0;
    InjectionPointCondition *condition = (InjectionPointCondition *) private_data;
 
    if (inj_state == NULL)
        injection_init_shmem();
 
    if (!injection_point_allowed(condition))
        return;
 
    pgstat_report_inj(name);
 
    /*
     * Use the injection point name for this custom wait event.  Note that
     * this custom wait event name is not released, but we don't care much for
     * testing as this should be short-lived.
     */
    injection_wait_event = WaitEventInjectionPointNew(name);
 
    /*
     * Find a free slot to wait for, and register this injection point's name.
     */
    SpinLockAcquire(&inj_state->lock);
    for (int i = 0; i < INJ_MAX_WAIT; i++)
    {
        if (inj_state->name[i][0] == '\0')
        {
            index = i;
            strlcpy(inj_state->name[i], name, INJ_NAME_MAXLEN);
            old_wait_counts = inj_state->wait_counts[i];
            break;
        }
    }
    SpinLockRelease(&inj_state->lock);
 
    if (index < 0)
        elog(ERROR, "could not find free slot for wait of injection point %s ",
             name);
 
    /* And sleep.. */
    ConditionVariablePrepareToSleep(&inj_state->wait_point);
    for (;;)
    {
        uint32      new_wait_counts;
 
        SpinLockAcquire(&inj_state->lock);
        new_wait_counts = inj_state->wait_counts[index];
        SpinLockRelease(&inj_state->lock);
 
        if (old_wait_counts != new_wait_counts)
            break;
        ConditionVariableSleep(&inj_state->wait_point, injection_wait_event);
    }
    ConditionVariableCancelSleep();
 
    /* Remove this injection point from the waiters. */
    SpinLockAcquire(&inj_state->lock);
    inj_state->name[index][0] = '\0';
    SpinLockRelease(&inj_state->lock);
}
 
/*
 * SQL function for creating an injection point.
 */
PG_FUNCTION_INFO_V1(injection_points_attach);
Datum
injection_points_attach(PG_FUNCTION_ARGS)
{
    char       *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
    char       *action = text_to_cstring(PG_GETARG_TEXT_PP(1));
    char       *function;
    InjectionPointCondition condition = {0};
 
    if (strcmp(action, "error") == 0)
        function = "injection_error";
    else if (strcmp(action, "notice") == 0)
        function = "injection_notice";
    else if (strcmp(action, "wait") == 0)
        function = "injection_wait";
    else
        elog(ERROR, "incorrect action \"%s\" for injection point creation", action);
 
    if (injection_point_local)
    {
        condition.type = INJ_CONDITION_PID;
        condition.pid = MyProcPid;
    }
 
    pgstat_report_inj_fixed(1, 0, 0, 0, 0);
    InjectionPointAttach(name, "injection_points", function, &condition,
                         sizeof(InjectionPointCondition));
 
    if (injection_point_local)
    {
        MemoryContext oldctx;
 
        /* Local injection point, so track it for automated cleanup */
        oldctx = MemoryContextSwitchTo(TopMemoryContext);
        inj_list_local = lappend(inj_list_local, makeString(pstrdup(name)));
        MemoryContextSwitchTo(oldctx);
    }
 
    /* Add entry for stats */
    pgstat_create_inj(name);
 
    PG_RETURN_VOID();
}
 
/*
 * SQL function for loading an injection point.
 */
PG_FUNCTION_INFO_V1(injection_points_load);
Datum
injection_points_load(PG_FUNCTION_ARGS)
{
    char       *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
    if (inj_state == NULL)
        injection_init_shmem();
 
    pgstat_report_inj_fixed(0, 0, 0, 0, 1);
    INJECTION_POINT_LOAD(name);
 
    PG_RETURN_VOID();
}
 
/*
 * SQL function for triggering an injection point.
 */
PG_FUNCTION_INFO_V1(injection_points_run);
Datum
injection_points_run(PG_FUNCTION_ARGS)
{
    char       *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
    pgstat_report_inj_fixed(0, 0, 1, 0, 0);
    INJECTION_POINT(name);
 
    PG_RETURN_VOID();
}
 
/*
 * SQL function for triggering an injection point from cache.
 */
PG_FUNCTION_INFO_V1(injection_points_cached);
Datum
injection_points_cached(PG_FUNCTION_ARGS)
{
    char       *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
    pgstat_report_inj_fixed(0, 0, 0, 1, 0);
    INJECTION_POINT_CACHED(name);
 
    PG_RETURN_VOID();
}
 
/*
 * SQL function for waking up an injection point waiting in injection_wait().
 */
PG_FUNCTION_INFO_V1(injection_points_wakeup);
Datum
injection_points_wakeup(PG_FUNCTION_ARGS)
{
    char       *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
    int         index = -1;
 
    if (inj_state == NULL)
        injection_init_shmem();
 
    /* First bump the wait counter for the injection point to wake up */
    SpinLockAcquire(&inj_state->lock);
    for (int i = 0; i < INJ_MAX_WAIT; i++)
    {
        if (strcmp(name, inj_state->name[i]) == 0)
        {
            index = i;
            break;
        }
    }
    if (index < 0)
    {
        SpinLockRelease(&inj_state->lock);
        elog(ERROR, "could not find injection point %s to wake up", name);
    }
    inj_state->wait_counts[index]++;
    SpinLockRelease(&inj_state->lock);
 
    /* And broadcast the change to the waiters */
    ConditionVariableBroadcast(&inj_state->wait_point);
    PG_RETURN_VOID();
}
 
/*
 * injection_points_set_local
 *
 * Track if any injection point created in this process ought to run only
 * in this process.  Such injection points are detached automatically when
 * this process exits.  This is useful to make test suites concurrent-safe.
 */
PG_FUNCTION_INFO_V1(injection_points_set_local);
Datum
injection_points_set_local(PG_FUNCTION_ARGS)
{
    /* Enable flag to add a runtime condition based on this process ID */
    injection_point_local = true;
 
    if (inj_state == NULL)
        injection_init_shmem();
 
    /*
     * Register a before_shmem_exit callback to remove any injection points
     * linked to this process.
     */
    before_shmem_exit(injection_points_cleanup, (Datum) 0);
 
    PG_RETURN_VOID();
}
 
/*
 * SQL function for dropping an injection point.
 */
PG_FUNCTION_INFO_V1(injection_points_detach);
Datum
injection_points_detach(PG_FUNCTION_ARGS)
{
    char       *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
    pgstat_report_inj_fixed(0, 1, 0, 0, 0);
    if (!InjectionPointDetach(name))
        elog(ERROR, "could not detach injection point \"%s\"", name);
 
    /* Remove point from local list, if required */
    if (inj_list_local != NIL)
    {
        MemoryContext oldctx;
 
        oldctx = MemoryContextSwitchTo(TopMemoryContext);
        inj_list_local = list_delete(inj_list_local, makeString(name));
        MemoryContextSwitchTo(oldctx);
    }
 
    /* Remove stats entry */
    pgstat_drop_inj(name);
 
    PG_RETURN_VOID();
}
 
 
void
_PG_init(void)
{
    if (!process_shared_preload_libraries_in_progress)
        return;
 
    DefineCustomBoolVariable("injection_points.stats",
                             "Enables statistics for injection points.",
                             NULL,
                             &inj_stats_enabled,
                             false,
                             PGC_POSTMASTER,
                             0,
                             NULL,
                             NULL,
                             NULL);
 
    MarkGUCPrefixReserved("injection_points");
 
    /* 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();
}