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MDL_lock encapsulation: MDL_lock::upgrade()

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Avoid accessing MDL_lock::m_granted and MDL_lock::m_rwlock from
MDL_ticket::upgrade_shared_lock(), use MDL_lock::upgrade() instead.

This is part of broader cleanup, which aims to make large part of
MDL_lock members private. It is needed to simplify further work on
MDEV-19749 - MDL scalability regression after backup locks.
This commit is contained in:
Sergey Vojtovich 2025-05-01 01:12:08 +04:00 committed by Sergei Golubchik
parent 49a290e00f
commit 84d85849a0
1 changed files with 22 additions and 14 deletions
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36
sql/mdl.cc
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@ -761,6 +761,25 @@ end:
mysql_prlock_unlock(&m_rwlock); mysql_prlock_unlock(&m_rwlock);
} }
/**
MDL_context::upgrade_shared_lock() helper
To update state of MDL_lock object correctly we need to temporarily
exclude ticket from the granted queue and then include it back.
*/
void upgrade(MDL_ticket *ticket, enum_mdl_type type,
MDL_ticket *remove)
{
mysql_prlock_wrlock(&m_rwlock);
if (remove)
m_granted.remove_ticket(remove);
m_granted.remove_ticket(ticket);
ticket->m_type= type;
m_granted.add_ticket(ticket);
mysql_prlock_unlock(&m_rwlock);
}
const MDL_lock_strategy *m_strategy; const MDL_lock_strategy *m_strategy;
private: private:
static const MDL_backup_lock m_backup_lock_strategy; static const MDL_backup_lock m_backup_lock_strategy;
@ -2677,20 +2696,9 @@ MDL_context::upgrade_shared_lock(MDL_ticket *mdl_ticket,
is_new_ticket= ! has_lock(mdl_svp, mdl_xlock_request.ticket); is_new_ticket= ! has_lock(mdl_svp, mdl_xlock_request.ticket);
/* Merge the acquired and the original lock. @todo: move to a method. */ /* Merge the acquired and the original lock. */
mysql_prlock_wrlock(&mdl_ticket->m_lock->m_rwlock); mdl_ticket->m_lock->upgrade(mdl_ticket, new_type,
if (is_new_ticket) is_new_ticket ? mdl_xlock_request.ticket : nullptr);
mdl_ticket->m_lock->m_granted.remove_ticket(mdl_xlock_request.ticket);
/*
Set the new type of lock in the ticket. To update state of
MDL_lock object correctly we need to temporarily exclude
ticket from the granted queue and then include it back.
*/
mdl_ticket->m_lock->m_granted.remove_ticket(mdl_ticket);
mdl_ticket->m_type= new_type;
mdl_ticket->m_lock->m_granted.add_ticket(mdl_ticket);
mysql_prlock_unlock(&mdl_ticket->m_lock->m_rwlock);
if (is_new_ticket) if (is_new_ticket)
{ {