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Removed redundant service_thread_count

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In contrast to thread_count, which is decremented by THD destructor,
this one was most probably intended to be decremented after all THD
destructors are done.

THD_count class was added to achieve similar effect with thread_count.

Aim is to reduce usage of LOCK_thread_count and COND_thread_count.
Part of MDEV-15135.
This commit is contained in:
Sergey Vojtovich
2019-01-22 22:45:26 +04:00
parent 3503fbbebf
commit 9824ec81aa
7 changed files with 49 additions and 65 deletions
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48
sql/sql_class.h
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@@ -2134,13 +2134,46 @@ struct wait_for_commit
extern "C" void my_message_sql(uint error, const char *str, myf MyFlags);
/**
A wrapper around thread_count.
It must be specified as a first base class of THD, so that increment is
done before any other THD constructors and decrement - after any other THD
destructors.
*/
struct THD_count
{
THD_count() { thread_count++; }
/**
Decrements thread_count.
Unblocks close_conneciton() if there are no more THD's left.
*/
~THD_count()
{
uint32_t t= thread_count--;
DBUG_ASSERT(t > 0);
if (t == 1)
{
mysql_mutex_lock(&LOCK_thread_count);
mysql_cond_broadcast(&COND_thread_count);
mysql_mutex_unlock(&LOCK_thread_count);
}
}
};
/**
@class THD
For each client connection we create a separate thread with THD serving as
a thread/connection descriptor
*/
class THD :public Statement,
class THD: public THD_count, /* this must be first */
public Statement,
/*
This is to track items changed during execution of a prepared
statement/stored procedure. It's created by
@@ -2165,19 +2198,6 @@ private:
inline bool is_conventional() const
{ DBUG_ASSERT(0); return Statement::is_conventional(); }
void dec_thread_count(void)
{
DBUG_ASSERT(thread_count > 0);
thread_safe_decrement32(&thread_count);
signal_thd_deleted();
}
void inc_thread_count(void)
{
thread_safe_increment32(&thread_count);
}
public:
MDL_context mdl_context;