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Kernel: Fix race conditions processing async device requests

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Tom 2021-02-06 16:59:32 -07:00 committed by Andreas Kling
parent 8177f2474b
commit 5ccc3637e3
4 changed files with 23 additions and 41 deletions
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14
Kernel/Devices/AsyncDeviceRequest.cpp
View file

@ -91,15 +91,11 @@ void AsyncDeviceRequest::add_sub_request(NonnullRefPtr<AsyncDeviceRequest> sub_r
VERIFY(sub_request->m_parent_request == nullptr);
sub_request->m_parent_request = this;
bool should_start;
{
ScopedSpinLock lock(m_lock);
VERIFY(!is_completed_result(m_result));
m_sub_requests_pending.append(sub_request);
should_start = (m_result == Started);
}
if (should_start)
sub_request->do_start();
ScopedSpinLock lock(m_lock);
VERIFY(!is_completed_result(m_result));
m_sub_requests_pending.append(sub_request);
if (m_result == Started)
sub_request->do_start(move(lock));
}
void AsyncDeviceRequest::sub_request_finished(AsyncDeviceRequest& sub_request)

20
Kernel/Devices/AsyncDeviceRequest.h
View file

@ -78,9 +78,14 @@ public:
[[nodiscard]] RequestWaitResult wait(Time* = nullptr);
void do_start(Badge<Device>)
void do_start(ScopedSpinLock<SpinLock<u8>>&& requests_lock)
{
do_start();
if (is_completed_result(m_result))
return;
m_result = Started;
requests_lock.unlock();
start();
}
void complete(RequestResult result);
@ -137,17 +142,6 @@ private:
void sub_request_finished(AsyncDeviceRequest&);
void request_finished();
void do_start()
{
{
ScopedSpinLock lock(m_lock);
if (is_completed_result(m_result))
return;
m_result = Started;
}
start();
}
bool in_target_context(const UserOrKernelBuffer& buffer) const
{
if (buffer.is_kernel_buffer())

19
Kernel/Devices/Device.cpp
View file

@ -82,20 +82,15 @@ String Device::absolute_path(const FileDescription&) const
void Device::process_next_queued_request(Badge<AsyncDeviceRequest>, const AsyncDeviceRequest& completed_request)
{
AsyncDeviceRequest* next_request = nullptr;
{
ScopedSpinLock lock(m_requests_lock);
VERIFY(!m_requests.is_empty());
VERIFY(m_requests.first().ptr() == &completed_request);
m_requests.remove(m_requests.begin());
if (!m_requests.is_empty())
next_request = m_requests.first().ptr();
ScopedSpinLock lock(m_requests_lock);
VERIFY(!m_requests.is_empty());
VERIFY(m_requests.first().ptr() == &completed_request);
m_requests.remove(m_requests.begin());
if (!m_requests.is_empty()) {
auto* next_request = m_requests.first().ptr();
next_request->do_start(move(lock));
}
if (next_request)
next_request->start();
evaluate_block_conditions();
}

11
Kernel/Devices/Device.h
View file

@ -72,14 +72,11 @@ public:
NonnullRefPtr<AsyncRequestType> make_request(Args&&... args)
{
auto request = adopt(*new AsyncRequestType(*this, forward<Args>(args)...));
bool was_empty;
{
ScopedSpinLock lock(m_requests_lock);
was_empty = m_requests.is_empty();
m_requests.append(request);
}
ScopedSpinLock lock(m_requests_lock);
bool was_empty = m_requests.is_empty();
m_requests.append(request);
if (was_empty)
request->do_start({});
request->do_start(move(lock));
return request;
}