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1111. [bug] Multithreaded servers could deadlock processing

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recursive queries due to a locking hieararchy
                        violation in adb.c. [RT #2017]
This commit is contained in:
Andreas Gustafsson
2001-11-07 22:40:33 +00:00
parent c9b0b5d9bf
commit 78bf1ca895
2 changed files with 33 additions and 32 deletions
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4
CHANGES
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@@ -1,3 +1,7 @@
1111. [bug] Multithreaded servers could deadlock processing
recursive queries due to a locking hieararchy
violation in adb.c. [RT #2017]
1110. [bug] dig only accept valid abbreviations of +options.
[RT #2003]

61
lib/dns/adb.c
View File

@@ -15,7 +15,7 @@
* WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id: adb.c,v 1.189 2001/11/07 04:25:15 marka Exp $ */
/* $Id: adb.c,v 1.190 2001/11/07 22:40:33 gson Exp $ */
/*
* Implementation notes
@@ -115,7 +115,7 @@ struct dns_adb {
unsigned int magic;
isc_mutex_t lock;
isc_mutex_t ilock;
isc_mutex_t reflock; /* Covers irefcnt, erefcnt */
isc_mem_t *mctx;
dns_view_t *view;
isc_timermgr_t *timermgr;
@@ -302,7 +302,7 @@ static void print_namehook_list(FILE *, const char *legend,
static void print_find_list(FILE *, dns_adbname_t *);
static void print_fetch_list(FILE *, dns_adbname_t *);
static inline void dec_adb_irefcnt(dns_adb_t *);
static inline void inc_adb_erefcnt(dns_adb_t *, isc_boolean_t);
static inline void inc_adb_erefcnt(dns_adb_t *);
static inline void dec_adb_erefcnt(dns_adb_t *, isc_boolean_t);
static inline void inc_entry_refcnt(dns_adb_t *, dns_adbentry_t *,
isc_boolean_t);
@@ -1184,18 +1184,16 @@ static inline void
check_exit(dns_adb_t *adb) {
isc_event_t *event;
isc_task_t *etask;
isc_boolean_t zeroirefcnt;
isc_boolean_t zeroirefcnt, zeroerefcnt;
/*
* The caller must be holding the adb lock.
*/
LOCK(&adb->ilock);
if (adb->irefcnt == 0)
zeroirefcnt = ISC_TRUE;
else
zeroirefcnt = ISC_FALSE;
UNLOCK(&adb->ilock);
LOCK(&adb->reflock);
zeroirefcnt = ISC_TF(adb->irefcnt == 0);
zeroerefcnt = ISC_TF(adb->erefcnt == 0);
UNLOCK(&adb->reflock);
if (adb->shutting_down && zeroirefcnt &&
isc_mempool_getallocated(adb->ahmp) == 0) {
@@ -1215,7 +1213,7 @@ check_exit(dns_adb_t *adb) {
* If there aren't any external references either, we're
* done. Send the control event to initiate shutdown.
*/
if (adb->erefcnt == 0) {
if (zeroerefcnt) {
INSIST(!adb->cevent_sent); /* Sanity check. */
event = &adb->cevent;
isc_task_send(adb->task, &event);
@@ -1226,34 +1224,36 @@ check_exit(dns_adb_t *adb) {
static inline void
dec_adb_irefcnt(dns_adb_t *adb) {
LOCK(&adb->ilock);
LOCK(&adb->reflock);
INSIST(adb->irefcnt > 0);
adb->irefcnt--;
UNLOCK(&adb->ilock);
UNLOCK(&adb->reflock);
}
static inline void
inc_adb_erefcnt(dns_adb_t *adb, isc_boolean_t lock) {
if (lock)
LOCK(&adb->lock);
inc_adb_erefcnt(dns_adb_t *adb) {
LOCK(&adb->reflock);
adb->erefcnt++;
if (lock)
UNLOCK(&adb->lock);
UNLOCK(&adb->reflock);
}
static inline void
dec_adb_erefcnt(dns_adb_t *adb, isc_boolean_t lock) {
isc_boolean_t zeroerefcnt;
if (lock)
LOCK(&adb->lock);
INSIST(adb->erefcnt > 0);
adb->erefcnt--;
if (adb->erefcnt == 0)
LOCK(&adb->reflock);
adb->erefcnt--;
zeroerefcnt = ISC_TF(adb->erefcnt == 0);
UNLOCK(&adb->reflock);
if (zeroerefcnt)
check_exit(adb);
if (lock)
@@ -2164,7 +2164,7 @@ destroy(dns_adb_t *adb) {
isc_mutexblock_destroy(adb->entrylocks, NBUCKETS);
isc_mutexblock_destroy(adb->namelocks, NBUCKETS);
DESTROYLOCK(&adb->ilock);
DESTROYLOCK(&adb->reflock);
DESTROYLOCK(&adb->lock);
DESTROYLOCK(&adb->mplock);
@@ -2234,7 +2234,7 @@ dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *timermgr,
if (result != ISC_R_SUCCESS)
goto fail0c;
result = isc_mutex_init(&adb->ilock);
result = isc_mutex_init(&adb->reflock);
if (result != ISC_R_SUCCESS)
goto fail0d;
@@ -2343,7 +2343,7 @@ dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *timermgr,
if (adb->af6mp != NULL)
isc_mempool_destroy(&adb->af6mp);
DESTROYLOCK(&adb->ilock);
DESTROYLOCK(&adb->reflock);
fail0d:
DESTROYLOCK(&adb->mplock);
fail0c:
@@ -2360,7 +2360,7 @@ dns_adb_attach(dns_adb_t *adb, dns_adb_t **adbx) {
REQUIRE(DNS_ADB_VALID(adb));
REQUIRE(adbx != NULL && *adbx == NULL);
inc_adb_erefcnt(adb, ISC_TRUE);
inc_adb_erefcnt(adb);
*adbx = adb;
}
@@ -2398,12 +2398,9 @@ dns_adb_whenshutdown(dns_adb_t *adb, isc_task_t *task, isc_event_t **eventp) {
LOCK(&adb->lock);
LOCK(&adb->ilock);
if (adb->irefcnt == 0)
zeroirefcnt = ISC_TRUE;
else
zeroirefcnt = ISC_FALSE;
UNLOCK(&adb->ilock);
LOCK(&adb->reflock);
zeroirefcnt = ISC_TF(adb->irefcnt == 0);
UNLOCK(&adb->reflock);
if (adb->shutting_down && zeroirefcnt &&
isc_mempool_getallocated(adb->ahmp) == 0) {