diff options
Diffstat (limited to 'module')
| -rw-r--r-- | module/zfs/dmu_objset.c | 10 | ||||
| -rw-r--r-- | module/zfs/dsl_pool.c | 7 | ||||
| -rw-r--r-- | module/zfs/rrwlock.c | 25 |
3 files changed, 38 insertions, 4 deletions
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c index bc1aa1286..823a15677 100644 --- a/module/zfs/dmu_objset.c +++ b/module/zfs/dmu_objset.c @@ -1784,7 +1784,15 @@ dmu_objset_find_dp_cb(void *arg) dmu_objset_find_ctx_t *dcp = arg; dsl_pool_t *dp = dcp->dc_dp; - dsl_pool_config_enter(dp, FTAG); + /* + * We need to get a pool_config_lock here, as there are several + * asssert(pool_config_held) down the stack. Getting a lock via + * dsl_pool_config_enter is risky, as it might be stalled by a + * pending writer. This would deadlock, as the write lock can + * only be granted when our parent thread gives up the lock. + * The _prio interface gives us priority over a pending writer. + */ + dsl_pool_config_enter_prio(dp, FTAG); dmu_objset_find_dp_impl(dcp); diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c index 5d804352d..23cf43862 100644 --- a/module/zfs/dsl_pool.c +++ b/module/zfs/dsl_pool.c @@ -1051,6 +1051,13 @@ dsl_pool_config_enter(dsl_pool_t *dp, void *tag) } void +dsl_pool_config_enter_prio(dsl_pool_t *dp, void *tag) +{ + ASSERT(!rrw_held(&dp->dp_config_rwlock, RW_READER)); + rrw_enter_read_prio(&dp->dp_config_rwlock, tag); +} + +void dsl_pool_config_exit(dsl_pool_t *dp, void *tag) { rrw_exit(&dp->dp_config_rwlock, tag); diff --git a/module/zfs/rrwlock.c b/module/zfs/rrwlock.c index 8e80166c7..29a22534e 100644 --- a/module/zfs/rrwlock.c +++ b/module/zfs/rrwlock.c @@ -159,8 +159,8 @@ rrw_destroy(rrwlock_t *rrl) refcount_destroy(&rrl->rr_linked_rcount); } -void -rrw_enter_read(rrwlock_t *rrl, void *tag) +static void +rrw_enter_read_impl(rrwlock_t *rrl, boolean_t prio, void *tag) { mutex_enter(&rrl->rr_lock); #if !defined(DEBUG) && defined(_KERNEL) @@ -176,7 +176,7 @@ rrw_enter_read(rrwlock_t *rrl, void *tag) ASSERT(refcount_count(&rrl->rr_anon_rcount) >= 0); while (rrl->rr_writer != NULL || (rrl->rr_writer_wanted && - refcount_is_zero(&rrl->rr_anon_rcount) && + refcount_is_zero(&rrl->rr_anon_rcount) && !prio && rrn_find(rrl) == NULL)) cv_wait(&rrl->rr_cv, &rrl->rr_lock); @@ -192,6 +192,25 @@ rrw_enter_read(rrwlock_t *rrl, void *tag) } void +rrw_enter_read(rrwlock_t *rrl, void *tag) +{ + rrw_enter_read_impl(rrl, B_FALSE, tag); +} + +/* + * take a read lock even if there are pending write lock requests. if we want + * to take a lock reentrantly, but from different threads (that have a + * relationship to each other), the normal detection mechanism to overrule + * the pending writer does not work, so we have to give an explicit hint here. + */ +void +rrw_enter_read_prio(rrwlock_t *rrl, void *tag) +{ + rrw_enter_read_impl(rrl, B_TRUE, tag); +} + + +void rrw_enter_write(rrwlock_t *rrl) { mutex_enter(&rrl->rr_lock); |