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Bug#36579 Dumping information about locks in use may lead to a server crash

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Dumping information about locks in use by sending a SIGHUP signal
to the server or by invoking the "mysqladmin debug" command may
lead to a server crash in debug builds or to undefined behavior in
production builds.

The problem was that a mutex that protects a lock object (THR_LOCK)
might have been destroyed before the lock object was actually removed
from the list of locks in use, causing a race condition with other
threads iterating over the list. The solution is to destroy the mutex
only after removing lock object from the list.

mysys/thr_lock.c:
  Destroy the mutex that protects the lock object only after removing
  the lock object from the list of locks in use.
This commit is contained in:
Davi Arnaut 2008-08-25 10:18:52 -03:00
parent c546559a62
commit 1ee4a3ac82
1 changed files with 1 additions and 1 deletions
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2
mysys/thr_lock.c
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@ -333,10 +333,10 @@ void thr_lock_init(THR_LOCK *lock)
void thr_lock_delete(THR_LOCK *lock) void thr_lock_delete(THR_LOCK *lock)
{ {
DBUG_ENTER("thr_lock_delete"); DBUG_ENTER("thr_lock_delete");
VOID(pthread_mutex_destroy(&lock->mutex));
pthread_mutex_lock(&THR_LOCK_lock); pthread_mutex_lock(&THR_LOCK_lock);
thr_lock_thread_list=list_delete(thr_lock_thread_list,&lock->list); thr_lock_thread_list=list_delete(thr_lock_thread_list,&lock->list);
pthread_mutex_unlock(&THR_LOCK_lock); pthread_mutex_unlock(&THR_LOCK_lock);
pthread_mutex_destroy(&lock->mutex);
DBUG_VOID_RETURN; DBUG_VOID_RETURN;
} }