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Kernel/USB: Make UHCI descriptor pool thread-safe

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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.
This commit is contained in:
b14ckcat 2022-07-13 19:02:58 -04:00 • committed by Linus Groh
parent 00e13b5b27
commit 6aea13e229
1 changed files with 7 additions and 0 deletions
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7
Kernel/Bus/USB/UHCI/UHCIDescriptorPool.h
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@ -9,6 +9,7 @@
#include <AK/NonnullOwnPtr.h> #include <AK/NonnullOwnPtr.h>
#include <AK/OwnPtr.h> #include <AK/OwnPtr.h>
#include <AK/Stack.h> #include <AK/Stack.h>
#include <Kernel/Locking/Spinlock.h>
#include <Kernel/Memory/MemoryManager.h> #include <Kernel/Memory/MemoryManager.h>
#include <Kernel/Memory/Region.h> #include <Kernel/Memory/Region.h>
#include <Kernel/StdLib.h> #include <Kernel/StdLib.h>
@ -38,6 +39,8 @@ public:
[[nodiscard]] T* try_take_free_descriptor() [[nodiscard]] T* try_take_free_descriptor()
{ {
SpinlockLocker locker(m_pool_lock);
// We're out of descriptors! // We're out of descriptors!
if (m_free_descriptor_stack.is_empty()) if (m_free_descriptor_stack.is_empty())
return nullptr; return nullptr;
@ -51,6 +54,8 @@ public:
void release_to_pool(T* ptr) void release_to_pool(T* ptr)
{ {
SpinlockLocker locker(m_pool_lock);
dbgln_if(UHCI_VERBOSE_DEBUG, "Returning descriptor @ {} to pool {}", ptr, m_pool_name); dbgln_if(UHCI_VERBOSE_DEBUG, "Returning descriptor @ {} to pool {}", ptr, m_pool_name);
if (!m_free_descriptor_stack.push(ptr)) if (!m_free_descriptor_stack.push(ptr))
dbgln("Failed to return descriptor to pool {}. Stack overflow!", m_pool_name); dbgln("Failed to return descriptor to pool {}. Stack overflow!", m_pool_name);
@ -78,5 +83,7 @@ private:
StringView m_pool_name; // Name of this pool StringView m_pool_name; // Name of this pool
NonnullOwnPtr<Memory::Region> m_pool_region; // Memory region where descriptors actually reside NonnullOwnPtr<Memory::Region> m_pool_region; // Memory region where descriptors actually reside
Stack<T*, PAGE_SIZE / sizeof(T)> m_free_descriptor_stack; // Stack of currently free descriptor pointers Stack<T*, PAGE_SIZE / sizeof(T)> m_free_descriptor_stack; // Stack of currently free descriptor pointers
Spinlock m_pool_lock;
}; };
} }