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Kernel: Add DoubleBuffer::try_create() factory method for OOM hardening

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We need to expose the ability for DoubleBuffer creation to expose
failure, as DoubleBuffer depends on KBuffer, which also has to be able
to expose failure during OOM.

We will remove the non OOM API once all users have been converted.
This commit is contained in:
Brian Gianforcaro 2021-08-01 01:40:07 -07:00 • committed by Andreas Kling
parent b6200a3ed8
commit f816abcbad
2 changed files with 24 additions and 9 deletions
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28
Kernel/DoubleBuffer.cpp
View file

@ -17,22 +17,36 @@ inline void DoubleBuffer::compute_lockfree_metadata()
m_space_for_writing = m_capacity - m_write_buffer->size;
}
OwnPtr<DoubleBuffer> DoubleBuffer::try_create(size_t capacity)
{
auto storage = KBuffer::try_create_with_size(capacity * 2, Region::Access::Read | Region::Access::Write, "DoubleBuffer");
if (!storage)
return {};
return adopt_own_if_nonnull(new (nothrow) DoubleBuffer(capacity, storage.release_nonnull()));
}
DoubleBuffer::DoubleBuffer(size_t capacity)
: DoubleBuffer(capacity, KBuffer::try_create_with_size(capacity * 2, Region::Access::Read | Region::Access::Write, "DoubleBuffer").release_nonnull())
{
}
DoubleBuffer::DoubleBuffer(size_t capacity, NonnullOwnPtr<KBuffer> storage)
: m_write_buffer(&m_buffer1)
, m_read_buffer(&m_buffer2)
, m_storage(KBuffer::create_with_size(capacity * 2, Region::Access::Read | Region::Access::Write, "DoubleBuffer"))
, m_storage(move(storage))
, m_capacity(capacity)
{
m_buffer1.data = m_storage.data();
m_buffer1.data = m_storage->data();
m_buffer1.size = 0;
m_buffer2.data = m_storage.data() + capacity;
m_buffer2.data = m_storage->data() + capacity;
m_buffer2.size = 0;
m_space_for_writing = capacity;
}
void DoubleBuffer::flip()
{
if (m_storage.is_null())
if (m_storage->is_null())
return;
VERIFY(m_read_buffer_index == m_read_buffer->size);
swap(m_read_buffer, m_write_buffer);
@ -43,7 +57,7 @@ void DoubleBuffer::flip()
KResultOr<size_t> DoubleBuffer::write(const UserOrKernelBuffer& data, size_t size)
{
if (!size || m_storage.is_null())
if (!size || m_storage->is_null())
return 0;
MutexLocker locker(m_lock);
size_t bytes_to_write = min(size, m_space_for_writing);
@ -59,7 +73,7 @@ KResultOr<size_t> DoubleBuffer::write(const UserOrKernelBuffer& data, size_t siz
KResultOr<size_t> DoubleBuffer::read(UserOrKernelBuffer& data, size_t size)
{
if (!size || m_storage.is_null())
if (!size || m_storage->is_null())
return 0;
MutexLocker locker(m_lock);
if (m_read_buffer_index >= m_read_buffer->size && m_write_buffer->size != 0)
@ -78,7 +92,7 @@ KResultOr<size_t> DoubleBuffer::read(UserOrKernelBuffer& data, size_t size)
KResultOr<size_t> DoubleBuffer::peek(UserOrKernelBuffer& data, size_t size)
{
if (!size || m_storage.is_null())
if (!size || m_storage->is_null())
return 0;
MutexLocker locker(m_lock);
if (m_read_buffer_index >= m_read_buffer->size && m_write_buffer->size != 0) {

5
Kernel/DoubleBuffer.h
View file

@ -16,8 +16,8 @@ namespace Kernel {
class DoubleBuffer {
public:
[[nodiscard]] static OwnPtr<DoubleBuffer> try_create(size_t capacity = 65536);
explicit DoubleBuffer(size_t capacity = 65536);
[[nodiscard]] KResultOr<size_t> write(const UserOrKernelBuffer&, size_t);
[[nodiscard]] KResultOr<size_t> write(const u8* data, size_t size)
{
@ -47,6 +47,7 @@ public:
}
private:
explicit DoubleBuffer(size_t capacity, NonnullOwnPtr<KBuffer> storage);
void flip();
void compute_lockfree_metadata();
@ -60,7 +61,7 @@ private:
InnerBuffer m_buffer1;
InnerBuffer m_buffer2;
KBuffer m_storage;
NonnullOwnPtr<KBuffer> m_storage;
Function<void()> m_unblock_callback;
size_t m_capacity { 0 };
size_t m_read_buffer_index { 0 };