Commit f87e4b4e authored by Marko Mäkelä's avatar Marko Mäkelä

Merge 10.5 into 10.6

parents c2ea036b 1b12e251
......@@ -281,25 +281,17 @@ the read requests for the whole area.
#ifndef UNIV_INNOCHECKSUM
void page_hash_latch::read_lock_wait()
{
auto l= read_lock_yield();
/* First, try busy spinning for a while. */
for (auto spin= srv_n_spin_wait_rounds; spin--; )
{
if (l & WRITER_PENDING)
ut_delay(srv_spin_wait_delay);
if (read_trylock())
return;
l= read_lock_yield();
}
/* Fall back to yielding to other threads. */
for (;;)
{
if (l & WRITER_PENDING)
do
os_thread_yield();
if (read_trylock())
return;
l= read_lock_yield();
}
while (!read_trylock());
}
void page_hash_latch::write_lock_wait()
......
......@@ -36,17 +36,24 @@ class rw_lock
/** Flag to indicate that write_lock() or write_lock_wait() is pending */
static constexpr uint32_t WRITER_PENDING= WRITER | WRITER_WAITING;
/** Yield a read lock request due to a conflict with a write lock.
@return the lock value */
uint32_t read_lock_yield()
{
uint32_t l= lock.fetch_sub(1, std::memory_order_relaxed);
DBUG_ASSERT(l & ~WRITER_PENDING);
return l;
}
/** Start waiting for an exclusive lock. */
void write_lock_wait_start()
{ lock.fetch_or(WRITER_WAITING, std::memory_order_relaxed); }
/** Try to acquire a shared lock.
@param l the value of the lock word
@return whether the lock was acquired */
bool read_trylock(uint32_t &l)
{
l= UNLOCKED;
while (!lock.compare_exchange_strong(l, l + 1, std::memory_order_acquire,
std::memory_order_relaxed))
{
DBUG_ASSERT(!(WRITER & l) || !(~WRITER_PENDING & l));
if (l & WRITER_PENDING)
return false;
}
return true;
}
/** Wait for an exclusive lock.
@return whether the exclusive lock was acquired */
bool write_lock_poll()
......@@ -80,8 +87,7 @@ class rw_lock
}
/** Try to acquire a shared lock.
@return whether the lock was acquired */
bool read_trylock()
{ return !(lock.fetch_add(1, std::memory_order_acquire) & WRITER_PENDING); }
bool read_trylock() { uint32_t l; return read_trylock(l); }
/** Try to acquire an exclusive lock.
@return whether the lock was acquired */
bool write_trylock()
......
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