diff options
Diffstat (limited to 'sql/xa.h')
| -rw-r--r-- | sql/xa.h | 151 |
1 files changed, 151 insertions, 0 deletions
@@ -16,17 +16,167 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */ +enum xa_states { XA_ACTIVE= 0, XA_IDLE, XA_PREPARED, XA_ROLLBACK_ONLY }; class XID_cache_element; +struct XID_cache_insert_element +{ + enum xa_states xa_state; + XID *xid; + XID_cache_element *xid_cache_element; + + XID_cache_insert_element(enum xa_states xa_state_arg, XID *xid_arg): + xa_state(xa_state_arg), xid(xid_arg) {} +}; + + +class XID_cache_element +{ + /* + m_state is used to prevent elements from being deleted while XA RECOVER + iterates xid cache and to prevent recovered elments from being acquired by + multiple threads. + + bits 1..29 are reference counter + bit 30 is RECOVERED flag + bit 31 is ACQUIRED flag (thread owns this xid) + bit 32 is unused + + Newly allocated and deleted elements have m_state set to 0. + + On lock() m_state is atomically incremented. It also creates load-ACQUIRE + memory barrier to make sure m_state is actually updated before furhter + memory accesses. Attempting to lock an element that has neither ACQUIRED + nor RECOVERED flag set returns failure and further accesses to element + memory are forbidden. + + On unlock() m_state is decremented. It also creates store-RELEASE memory + barrier to make sure m_state is actually updated after preceding memory + accesses. + + ACQUIRED flag is set when thread registers it's xid or when thread acquires + recovered xid. + + RECOVERED flag is set for elements found during crash recovery. + + ACQUIRED and RECOVERED flags are cleared before element is deleted from + hash in a spin loop, after last reference is released. + */ + std::atomic<int32_t> m_state; +public: + static const int32 ACQUIRED= 1 << 30; + static const int32 RECOVERED= 1 << 29; + /* Error reported by the Resource Manager (RM) to the Transaction Manager. */ + uint rm_error; + enum xa_states xa_state; + XID xid; + bool is_set(int32_t flag) + { return m_state.load(std::memory_order_relaxed) & flag; } + void set(int32_t flag) + { + DBUG_ASSERT(!is_set(ACQUIRED | RECOVERED)); + m_state.fetch_add(flag, std::memory_order_relaxed); + } + bool lock() + { + int32_t old= m_state.fetch_add(1, std::memory_order_acquire); + if (old & (ACQUIRED | RECOVERED)) + return true; + unlock(); + return false; + } + void unlock() + { m_state.fetch_sub(1, std::memory_order_release); } + void mark_uninitialized() + { + int32_t old= ACQUIRED; + while (!m_state.compare_exchange_weak(old, 0, + std::memory_order_relaxed, + std::memory_order_relaxed)) + { + old&= ACQUIRED | RECOVERED; + (void) LF_BACKOFF(); + } + } + void acquired_to_recovered() + { + m_state.fetch_or(RECOVERED, std::memory_order_relaxed); + m_state.fetch_and(~ACQUIRED, std::memory_order_release); + } + bool acquire_recovered() + { + int32_t old= RECOVERED; + while (!m_state.compare_exchange_weak(old, ACQUIRED | RECOVERED, + std::memory_order_acquire, + std::memory_order_relaxed)) + { + if (!(old & RECOVERED) || (old & ACQUIRED)) + return false; + old= RECOVERED; + (void) LF_BACKOFF(); + } + return true; + } + static void lf_hash_initializer(LF_HASH *hash __attribute__((unused)), + XID_cache_element *element, + XID_cache_insert_element *new_element) + { + DBUG_ASSERT(!element->is_set(ACQUIRED | RECOVERED)); + element->rm_error= 0; + element->xa_state= new_element->xa_state; + element->xid.set(new_element->xid); + new_element->xid_cache_element= element; + } + static void lf_alloc_constructor(uchar *ptr) + { + XID_cache_element *element= (XID_cache_element*) (ptr + LF_HASH_OVERHEAD); + element->m_state= 0; + } + static void lf_alloc_destructor(uchar *ptr) + { + XID_cache_element *element= (XID_cache_element*) (ptr + LF_HASH_OVERHEAD); + DBUG_ASSERT(!element->is_set(ACQUIRED)); + } + static uchar *key(const XID_cache_element *element, size_t *length, + my_bool not_used __attribute__((unused))) + { + *length= element->xid.key_length(); + return element->xid.key(); + } +}; + + struct XID_STATE { XID_cache_element *xid_cache_element; + /* + Binary logging status. + It is set to TRUE at XA PREPARE if the transaction was written + to the binlog. + Naturally FALSE means the transaction was not written to + the binlog. Happens if the trnasaction did not modify anything + or binlogging was turned off. In that case we shouldn't binlog + the consequent XA COMMIT/ROLLBACK. + The recovered transaction after server restart sets it to TRUE always. + That can cause inconsistencies (shoud be fixed?). + */ + bool is_binlogged; bool check_has_uncommitted_xa() const; bool is_explicit_XA() const { return xid_cache_element != 0; } void set_error(uint error); void er_xaer_rmfail() const; XID *get_xid() const; + void reset() + { + //TODO: what's an equivalent + //xid.null(); + is_binlogged= false; + } + void set_binlogged() + { is_binlogged= true; } + void unset_binlogged() + { is_binlogged= false; } }; void xid_cache_init(void); @@ -42,3 +192,4 @@ bool trans_xa_commit(THD *thd); bool trans_xa_rollback(THD *thd); bool trans_xa_detach(THD *thd); bool mysql_xa_recover(THD *thd); +bool applier_reset_xa_trans(THD *thd); |