cpython-source-deps/env/env_failchk.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2005,2008 Oracle.  All rights reserved.
 *
 * $Id: env_failchk.c 63573 2008-05-23 21:43:21Z trent.nelson $
 */

#include "db_config.h"

#include "db_int.h"
#ifndef HAVE_SIMPLE_THREAD_TYPE
#include "dbinc/db_page.h"
#include "dbinc/hash.h"			/* Needed for call to __ham_func5. */
#endif
#include "dbinc/lock.h"
#include "dbinc/log.h"
#include "dbinc/mp.h"
#include "dbinc/txn.h"

static int __env_in_api __P((ENV *));
static void __env_clear_state __P((ENV *));

/*
 * __env_failchk_pp --
 *	ENV->failchk pre/post processing.
 *
 * PUBLIC: int __env_failchk_pp __P((DB_ENV *, u_int32_t));
 */
int
__env_failchk_pp(dbenv, flags)
	DB_ENV *dbenv;
	u_int32_t flags;
{
	DB_THREAD_INFO *ip;
	ENV *env;
	int ret;

	env = dbenv->env;

	ENV_ILLEGAL_BEFORE_OPEN(env, "DB_ENV->failchk");

	/*
	 * ENV->failchk requires self and is-alive functions.  We
	 * have a default self function, but no is-alive function.
	 */
	if (!ALIVE_ON(env)) {
		__db_errx(env,
	"DB_ENV->failchk requires DB_ENV->is_alive be configured");
		return (EINVAL);
	}

	if (flags != 0)
		return (__db_ferr(env, "DB_ENV->failchk", 0));

	ENV_ENTER(env, ip);

	/*
	 * We check for dead threads in the API first as this would be likely
	 * to hang other things we try later, like locks and transactions.
	 */
	if ((ret = __env_in_api(env)) != 0)
		goto err;

	if (LOCKING_ON(env) && (ret = __lock_failchk(env)) != 0)
		goto err;

	if (TXN_ON(env) &&
	    ((ret = __txn_failchk(env)) != 0 ||
	    (ret = __dbreg_failchk(env)) != 0))
		goto err;

	/* Mark any dead blocked threads as dead. */
	__env_clear_state(env);

#ifdef HAVE_MUTEX_SUPPORT
	ret = __mut_failchk(env);
#endif

err:	ENV_LEAVE(env, ip);
	return (ret);
}

/*
 * __env_thread_init --
 *	Initialize the thread control block table.
 *
 * PUBLIC: int __env_thread_init __P((ENV *, int));
 */
int
__env_thread_init(env, during_creation)
	ENV *env;
	int during_creation;
{
	DB_ENV *dbenv;
	DB_HASHTAB *htab;
	REGENV *renv;
	REGINFO *infop;
	THREAD_INFO *thread;
	int ret;

	dbenv = env->dbenv;
	infop = env->reginfo;
	renv = infop->primary;

	if (renv->thread_off == INVALID_ROFF) {
		if (dbenv->thr_max == 0) {
			env->thr_hashtab = NULL;
			if (ALIVE_ON(env)) {
				__db_errx(env,
		"is_alive method specified but no thread region allocated");
				return (EINVAL);
			}
			return (0);
		}

		if (!during_creation) {
			__db_errx(env,
    "thread table must be allocated when the database environment is created");
			return (EINVAL);
		}

		if ((ret =
		    __env_alloc(infop, sizeof(THREAD_INFO), &thread)) != 0) {
			__db_err(env, ret,
			     "unable to allocate a thread status block");
			return (ret);
		}
		memset(thread, 0, sizeof(*thread));
		renv->thread_off = R_OFFSET(infop, thread);
		/*
		 * Set the number of buckets to be 1/8th the number of
		 * thread control blocks.  This is rather arbitrary.
		 */
		thread->thr_nbucket = __db_tablesize(dbenv->thr_max / 8);
		if ((ret = __env_alloc(infop,
		     thread->thr_nbucket * sizeof(DB_HASHTAB), &htab)) != 0)
			return (ret);
		thread->thr_hashoff = R_OFFSET(infop, htab);
		__db_hashinit(htab, thread->thr_nbucket);
		thread->thr_max = dbenv->thr_max;
	} else {
		thread = R_ADDR(infop, renv->thread_off);
		htab = R_ADDR(infop, thread->thr_hashoff);
	}

	env->thr_hashtab = htab;
	env->thr_nbucket = thread->thr_nbucket;
	dbenv->thr_max = thread->thr_max;
	return (0);
}

/*
 * __env_thread_destroy --
 *	Destroy the thread control block table.
 *
 * PUBLIC: void __env_thread_destroy __P((ENV *));
 */
void
__env_thread_destroy(env)
	ENV *env;
{
	DB_HASHTAB *htab;
	DB_THREAD_INFO *ip, *np;
	REGENV *renv;
	REGINFO *infop;
	THREAD_INFO *thread;
	u_int32_t i;

	infop = env->reginfo;
	renv = infop->primary;
	if (renv->thread_off == INVALID_ROFF)
		return;

	thread = R_ADDR(infop, renv->thread_off);
	if ((htab = env->thr_hashtab) != NULL) {
		for (i = 0; i < env->thr_nbucket; i++) {
			ip = SH_TAILQ_FIRST(&htab[i], __db_thread_info);
			for (; ip != NULL; ip = np) {
				np = SH_TAILQ_NEXT(ip,
				    dbth_links, __db_thread_info);
				__env_alloc_free(infop, ip);
			}
		}
		__env_alloc_free(infop, htab);
	}

	__env_alloc_free(infop, thread);
	return;
}

/*
 * __env_in_api --
 *	Look for threads which died in the api and complain.
 *	If no threads died but there are blocked threads unpin
 *	any buffers they may have locked.
 */
static int
__env_in_api(env)
	ENV *env;
{
	DB_ENV *dbenv;
	DB_HASHTAB *htab;
	DB_THREAD_INFO *ip;
	REGENV *renv;
	REGINFO *infop;
	THREAD_INFO *thread;
	u_int32_t i;
	int unpin, ret;

	if ((htab = env->thr_hashtab) == NULL)
		return (EINVAL);

	dbenv = env->dbenv;
	infop = env->reginfo;
	renv = infop->primary;
	thread = R_ADDR(infop, renv->thread_off);
	unpin = 0;

	for (i = 0; i < env->thr_nbucket; i++)
		SH_TAILQ_FOREACH(ip, &htab[i], dbth_links, __db_thread_info) {
			if (ip->dbth_state == THREAD_SLOT_NOT_IN_USE ||
			    (ip->dbth_state == THREAD_OUT &&
			    thread->thr_count <  thread->thr_max))
				continue;
			if (dbenv->is_alive(
			    dbenv, ip->dbth_pid, ip->dbth_tid, 0))
				continue;
			if (ip->dbth_state == THREAD_BLOCKED) {
				ip->dbth_state = THREAD_BLOCKED_DEAD;
				unpin = 1;
				continue;
			}
			if (ip->dbth_state == THREAD_OUT) {
				ip->dbth_state = THREAD_SLOT_NOT_IN_USE;
				continue;
			}
			return (__db_failed(env,
			     "Thread died in Berkeley DB library",
			     ip->dbth_pid, ip->dbth_tid));
		}

	if (unpin == 0)
		return (0);

	for (i = 0; i < env->thr_nbucket; i++)
		SH_TAILQ_FOREACH(ip, &htab[i], dbth_links, __db_thread_info)
			if (ip->dbth_state == THREAD_BLOCKED_DEAD &&
			    (ret = __memp_unpin_buffers(env, ip)) != 0)
				return (ret);

	return (0);
}

/*
 * __env_clear_state --
 *	Look for threads which died while blockedi and clear them..
 */
static void
__env_clear_state(env)
	ENV *env;
{
	DB_HASHTAB *htab;
	DB_THREAD_INFO *ip;
	u_int32_t i;

	htab = env->thr_hashtab;
	for (i = 0; i < env->thr_nbucket; i++)
		SH_TAILQ_FOREACH(ip, &htab[i], dbth_links, __db_thread_info)
			if (ip->dbth_state == THREAD_BLOCKED_DEAD)
				ip->dbth_state = THREAD_SLOT_NOT_IN_USE;
}

struct __db_threadid {
	pid_t pid;
	db_threadid_t tid;
};

/*
 * PUBLIC: int __env_set_state __P((ENV *, DB_THREAD_INFO **, DB_THREAD_STATE));
 */
int
__env_set_state(env, ipp, state)
	ENV *env;
	DB_THREAD_INFO **ipp;
	DB_THREAD_STATE state;
{
	struct __db_threadid id;
	DB_ENV *dbenv;
	DB_HASHTAB *htab;
	DB_THREAD_INFO *ip;
	REGENV *renv;
	REGINFO *infop;
	THREAD_INFO *thread;
	u_int32_t indx;
	int ret;

	dbenv = env->dbenv;
	htab = env->thr_hashtab;

	dbenv->thread_id(dbenv, &id.pid, &id.tid);

	/*
	 * Hashing of thread ids.  This is simple but could be replaced with
	 * something more expensive if needed.
	 */
#ifdef HAVE_SIMPLE_THREAD_TYPE
	/*
	 * A thread ID may be a pointer, so explicitly cast to a pointer of
	 * the appropriate size before doing the bitwise XOR.
	 */
	indx = (u_int32_t)((uintptr_t)id.pid ^ (uintptr_t)id.tid);
#else
	indx = __ham_func5(NULL, &id.tid, sizeof(id.tid));
#endif
	indx %= env->thr_nbucket;
	SH_TAILQ_FOREACH(ip, &htab[indx], dbth_links, __db_thread_info) {
#ifdef HAVE_SIMPLE_THREAD_TYPE
		if (id.pid == ip->dbth_pid && id.tid == ip->dbth_tid)
			break;
#else
		if (memcmp(&id.pid, &ip->dbth_pid, sizeof(id.pid)) != 0)
			continue;
		if (memcmp(&id.tid, &ip->dbth_tid, sizeof(id.tid)) != 0)
			continue;
		break;
#endif
	}

#ifdef DIAGNOSTIC
	/* A check to ensure the thread of control has been registered. */
	if (state == THREAD_VERIFY) {
		DB_ASSERT(env, ip != NULL && ip->dbth_state != THREAD_OUT);
		return (0);
	}
#endif

	*ipp = NULL;
	ret = 0;
	if (ip == NULL) {
		infop = env->reginfo;
		renv = infop->primary;
		thread = R_ADDR(infop, renv->thread_off);
		MUTEX_LOCK(env, renv->mtx_regenv);

		/*
		 * If we are passed the specified max, try to reclaim one from
		 * our queue.  If failcheck has marked the slot not in use, we
		 * can take it, otherwise we must call is_alive before freeing
		 * it.
		 */
		if (thread->thr_count >= thread->thr_max) {
			SH_TAILQ_FOREACH(
			    ip, &htab[indx], dbth_links, __db_thread_info)
				if (ip->dbth_state == THREAD_SLOT_NOT_IN_USE ||
				    (ip->dbth_state == THREAD_OUT &&
				    ALIVE_ON(env) && !dbenv->is_alive(
				    dbenv, ip->dbth_pid, ip->dbth_tid, 0)))
					break;

			if (ip != NULL) {
				DB_ASSERT(env, ip->dbth_pincount == 0);
				goto init;
			}
		}

		thread->thr_count++;
		if ((ret = __env_alloc(infop,
		     sizeof(DB_THREAD_INFO), &ip)) == 0) {
			memset(ip, 0, sizeof(*ip));
			/*
			 * This assumes we can link atomically since we do
			 * no locking here.  We never use the backpointer
			 * so we only need to be able to write an offset
			 * atomically.
			 */
			SH_TAILQ_INSERT_HEAD(
			    &htab[indx], ip, dbth_links, __db_thread_info);
			ip->dbth_pincount = 0;
			ip->dbth_pinmax = PINMAX;
			ip->dbth_pinlist = R_OFFSET(infop, ip->dbth_pinarray);

init:			ip->dbth_pid = id.pid;
			ip->dbth_tid = id.tid;
			ip->dbth_state = state;
		}
		MUTEX_UNLOCK(env, renv->mtx_regenv);
	} else
		ip->dbth_state = state;
	*ipp = ip;

	return (ret);
}

/*
 * __env_thread_id_string --
 *	Convert a thread id to a string.
 *
 * PUBLIC: char *__env_thread_id_string
 * PUBLIC:     __P((DB_ENV *, pid_t, db_threadid_t, char *));
 */
char *
__env_thread_id_string(dbenv, pid, tid, buf)
	DB_ENV *dbenv;
	pid_t pid;
	db_threadid_t tid;
	char *buf;
{
#ifdef HAVE_SIMPLE_THREAD_TYPE
#ifdef UINT64_FMT
	char fmt[20];

	snprintf(fmt, sizeof(fmt), "%s/%s", UINT64_FMT, UINT64_FMT);
	snprintf(buf,
	    DB_THREADID_STRLEN, fmt, (u_int64_t)pid, (u_int64_t)(uintptr_t)tid);
#else
	snprintf(buf, DB_THREADID_STRLEN, "%lu/%lu", (u_long)pid, (u_long)tid);
#endif
#else
#ifdef UINT64_FMT
	char fmt[20];

	snprintf(fmt, sizeof(fmt), "%s/TID", UINT64_FMT);
	snprintf(buf, DB_THREADID_STRLEN, fmt, (u_int64_t)pid);
#else
	snprintf(buf, DB_THREADID_STRLEN, "%lu/TID", (u_long)pid);
#endif
#endif
	COMPQUIET(dbenv, NULL);
	COMPQUIET(*(u_int8_t *)&tid, 0);

	return (buf);
}