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Kernel/USB: Make UHCI descriptor pool thread-safe
Right now the TD and QH descriptor pools look to be susceptible to a race condition in the event they are accessed simultaneously by separate threads making USB transfers. This fix does not seem to add any noticeable overhead.
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1 changed files with 7 additions and 0 deletions
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@ -9,6 +9,7 @@
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#include <AK/NonnullOwnPtr.h>
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#include <AK/OwnPtr.h>
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#include <AK/Stack.h>
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#include <Kernel/Locking/Spinlock.h>
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#include <Kernel/Memory/MemoryManager.h>
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#include <Kernel/Memory/Region.h>
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#include <Kernel/StdLib.h>
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@ -38,6 +39,8 @@ public:
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[[nodiscard]] T* try_take_free_descriptor()
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{
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SpinlockLocker locker(m_pool_lock);
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// We're out of descriptors!
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if (m_free_descriptor_stack.is_empty())
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return nullptr;
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@ -51,6 +54,8 @@ public:
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void release_to_pool(T* ptr)
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{
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SpinlockLocker locker(m_pool_lock);
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dbgln_if(UHCI_VERBOSE_DEBUG, "Returning descriptor @ {} to pool {}", ptr, m_pool_name);
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if (!m_free_descriptor_stack.push(ptr))
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dbgln("Failed to return descriptor to pool {}. Stack overflow!", m_pool_name);
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@ -78,5 +83,7 @@ private:
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StringView m_pool_name; // Name of this pool
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NonnullOwnPtr<Memory::Region> m_pool_region; // Memory region where descriptors actually reside
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Stack<T*, PAGE_SIZE / sizeof(T)> m_free_descriptor_stack; // Stack of currently free descriptor pointers
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Spinlock m_pool_lock;
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};
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}
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