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MDEV-25371 Potential hang in wsrep_is_BF_lock_timeout()

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In commit e71e6133535da8d5eab86e504f0b116a03680780 (MDEV-24671),
lock_sys.wait_mutex was moved above lock_sys.mutex
(which was later replaced with lock_sys.latch) in the latching order.

In commit 7cf4419fc4874a31d6242699dadbfe470ce5626c (MDEV-24789),
a potential hang was introduced to Galera. The function lock_wait()
would hold lock_sys.wait_mutex while invoking wsrep_is_BF_lock_timeout(),
which in turn could acquire LockMutexGuard for some diagnostic printout.

wsrep_is_BF_lock_timeout(): Do not invoke trx_print_latched() or
LockMutexGuard.

lock_sys_t::wr_lock(), lock_sys_t::rd_lock(): Assert that the current
thread is not holding lock_sys.wait_mutex.
Unfortunately, RW-locks are not covered by SAFE_MUTEX.

Reviewed by: Jan Lindström
This commit is contained in:
Marko Mäkelä 2021-04-08 13:32:16 +03:00
parent 1900c2ede5
commit 7c524d4414
2 changed files with 4 additions and 4 deletions
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2
storage/innobase/include/lock0lock.h
View File

@ -703,6 +703,7 @@ public:
/** Acquire exclusive lock_sys.latch */
void wr_lock()
{
mysql_mutex_assert_not_owner(&wait_mutex);
ut_ad(!is_writer());
latch.wr_lock();
ut_ad(!writer.exchange(os_thread_get_curr_id(),
@ -718,6 +719,7 @@ public:
/** Acquire shared lock_sys.latch */
void rd_lock()
{
mysql_mutex_assert_not_owner(&wait_mutex);
ut_ad(!is_writer());
latch.rd_lock();
ut_ad(!writer.load(std::memory_order_relaxed));

6
storage/innobase/lock/lock0lock.cc
View File

@ -391,6 +391,7 @@ void lock_sys_t::create(ulint n_cells)
/** Acquire exclusive lock_sys.latch */
void lock_sys_t::wr_lock(const char *file, unsigned line)
{
mysql_mutex_assert_not_owner(&wait_mutex);
latch.wr_lock(file, line);
ut_ad(!writer.exchange(os_thread_get_curr_id(), std::memory_order_relaxed));
}
@ -405,6 +406,7 @@ void lock_sys_t::wr_unlock()
/** Acquire shared lock_sys.latch */
void lock_sys_t::rd_lock(const char *file, unsigned line)
{
mysql_mutex_assert_not_owner(&wait_mutex);
latch.rd_lock(file, line);
ut_ad(!writer.load(std::memory_order_relaxed));
ut_d(readers.fetch_add(1, std::memory_order_relaxed));
@ -549,10 +551,6 @@ ATTRIBUTE_NOINLINE static bool wsrep_is_BF_lock_timeout(const trx_t &trx)
ib::info() << "WSREP: BF lock wait long for trx:" << ib::hex(trx.id)
<< " query: " << wsrep_thd_query(trx.mysql_thd);
{
LockMutexGuard g{SRW_LOCK_CALL};
trx_print_latched(stderr, &trx, 3000);
}
srv_print_innodb_monitor= true;
srv_print_innodb_lock_monitor= true;