Function ConditionalLockBuffer

src/backend/storage/buffer/bufmgr.c:4315–4327

* Acquire the content_lock for the buffer, but only if we don't have to wait. * * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode. */

 * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
 */
bool
ConditionalLockBuffer(Buffer buffer)
{
	BufferDesc *buf;

	Assert(BufferIsPinned(buffer));
	if (BufferIsLocal(buffer))
		return true;			/* act as though we got it */

	buf = GetBufferDescriptor(buffer - 1);

	return ConditionalAcquireContentLock(buf, LW_EXCLUSIVE);
}

/*
 * LockBufferForCleanup - lock a buffer in preparation for deleting items