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046d6855f5
This makes the Scheduler a lot leaner by not having to evaluate block conditions every time it is invoked. Instead evaluate them as the states change, and unblock threads at that point. This also implements some more waitid/waitpid/wait features and behavior. For example, WUNTRACED and WNOWAIT are now supported. And wait will now not return EINTR when SIGCHLD is delivered at the same time.
98 lines
3.5 KiB
C++
98 lines
3.5 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <AK/StringView.h>
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#include <Kernel/DoubleBuffer.h>
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namespace Kernel {
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inline void DoubleBuffer::compute_lockfree_metadata()
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{
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InterruptDisabler disabler;
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m_empty = m_read_buffer_index >= m_read_buffer->size && m_write_buffer->size == 0;
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m_space_for_writing = m_capacity - m_write_buffer->size;
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}
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DoubleBuffer::DoubleBuffer(size_t capacity)
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: m_write_buffer(&m_buffer1)
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, m_read_buffer(&m_buffer2)
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, m_storage(KBuffer::create_with_size(capacity * 2, Region::Access::Read | Region::Access::Write, "DoubleBuffer"))
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, m_capacity(capacity)
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{
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m_buffer1.data = m_storage.data();
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m_buffer1.size = 0;
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m_buffer2.data = m_storage.data() + capacity;
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m_buffer2.size = 0;
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m_space_for_writing = capacity;
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}
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void DoubleBuffer::flip()
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{
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ASSERT(m_read_buffer_index == m_read_buffer->size);
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swap(m_read_buffer, m_write_buffer);
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m_write_buffer->size = 0;
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m_read_buffer_index = 0;
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compute_lockfree_metadata();
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}
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ssize_t DoubleBuffer::write(const UserOrKernelBuffer& data, size_t size)
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{
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if (!size)
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return 0;
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ASSERT(size > 0);
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LOCKER(m_lock);
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size_t bytes_to_write = min(size, m_space_for_writing);
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u8* write_ptr = m_write_buffer->data + m_write_buffer->size;
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m_write_buffer->size += bytes_to_write;
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compute_lockfree_metadata();
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if (!data.read(write_ptr, bytes_to_write))
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return -EFAULT;
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if (m_unblock_callback && !m_empty)
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m_unblock_callback();
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return (ssize_t)bytes_to_write;
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}
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ssize_t DoubleBuffer::read(UserOrKernelBuffer& data, size_t size)
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{
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if (!size)
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return 0;
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ASSERT(size > 0);
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LOCKER(m_lock);
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if (m_read_buffer_index >= m_read_buffer->size && m_write_buffer->size != 0)
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flip();
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if (m_read_buffer_index >= m_read_buffer->size)
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return 0;
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size_t nread = min(m_read_buffer->size - m_read_buffer_index, size);
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if (!data.write(m_read_buffer->data + m_read_buffer_index, nread))
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return -EFAULT;
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m_read_buffer_index += nread;
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compute_lockfree_metadata();
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if (m_unblock_callback && m_space_for_writing > 0)
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m_unblock_callback();
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return (ssize_t)nread;
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}
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}
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