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lvmetad: Avoid overlapping locks that could cause a deadlock (BZ 862253).

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This commit is contained in:
Petr Rockai 2012-10-08 09:12:51 +02:00
parent 0dfafd77d4
commit 6e312c56ad
1 changed files with 12 additions and 4 deletions
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16
daemons/lvmetad/lvmetad-core.c
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@ -38,6 +38,7 @@ typedef struct {
struct dm_hash_table *pvid_to_vgid;
struct {
struct dm_hash_table *vg;
pthread_mutex_t vg_lock_map;
pthread_mutex_t pvid_to_pvmeta;
pthread_mutex_t vgid_to_metadata;
pthread_mutex_t pvid_to_vgid;
@ -112,7 +113,7 @@ static struct dm_config_tree *lock_vg(lvmetad_state *s, const char *id) {
pthread_mutex_t *vg;
struct dm_config_tree *cft;
lock_vgid_to_metadata(s);
pthread_mutex_lock(&s->lock.vg_lock_map);
vg = dm_hash_lookup(s->lock.vg, id);
if (!vg) {
pthread_mutexattr_t rec;
@ -126,8 +127,14 @@ static struct dm_config_tree *lock_vg(lvmetad_state *s, const char *id) {
return NULL;
}
}
/* We never remove items from s->lock.vg => the pointer remains valid. */
pthread_mutex_unlock(&s->lock.vg_lock_map);
DEBUG(s, "locking VG %s", id);
pthread_mutex_lock(vg);
/* Protect against structure changes of the vgid_to_metadata hash. */
lock_vgid_to_metadata(s);
cft = dm_hash_lookup(s->vgid_to_metadata, id);
unlock_vgid_to_metadata(s);
return cft;
@ -137,11 +144,11 @@ static void unlock_vg(lvmetad_state *s, const char *id) {
pthread_mutex_t *vg;
DEBUG(s, "unlocking VG %s", id);
lock_vgid_to_metadata(s); /* someone might be changing the s->lock.vg structure right
* now, so avoid stepping on each other's toes */
/* Protect the s->lock.vg structure from concurrent access. */
pthread_mutex_lock(&s->lock.vg_lock_map);
if ((vg = dm_hash_lookup(s->lock.vg, id)))
pthread_mutex_unlock(vg);
unlock_vgid_to_metadata(s);
pthread_mutex_unlock(&s->lock.vg_lock_map);
}
static struct dm_config_node *pvs(struct dm_config_node *vg)
@ -975,6 +982,7 @@ static int init(daemon_state *s)
pthread_mutex_init(&ls->lock.pvid_to_pvmeta, &rec);
pthread_mutex_init(&ls->lock.vgid_to_metadata, &rec);
pthread_mutex_init(&ls->lock.pvid_to_vgid, NULL);
pthread_mutex_init(&ls->lock.vg_lock_map, NULL);
pthread_mutex_init(&ls->token_lock, NULL);
create_metadata_hashes(ls);