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Fix result returned by MutexLock

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`MutexLock` incorrectly returned `InvalidCurrentMemory` for cases where the userspace value didn't match the expected value. It's been corrected to return no error in those cases while preserving the error code for usage in `ConditionalVariableWait`.
This commit is contained in:
PixelyIon 2022-11-26 00:36:46 +05:30 committed by Mark Collins
parent 08ef88b156
commit 6bbe9de881
2 changed files with 8 additions and 10 deletions
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15
app/src/main/cpp/skyline/kernel/types/KProcess.cpp
View File

@ -111,15 +111,15 @@ namespace skyline::kernel::type {
constexpr u32 HandleWaitersBit{1UL << 30}; //!< A bit which denotes if a mutex psuedo-handle has waiters or not
Result KProcess::MutexLock(u32 *mutex, KHandle ownerHandle, KHandle tag) {
Result KProcess::MutexLock(u32 *mutex, KHandle ownerHandle, KHandle tag, bool failOnOutdated) {
TRACE_EVENT_FMT("kernel", "MutexLock 0x{:X}", mutex);
std::shared_ptr<KThread> owner;
try {
owner = GetHandle<KThread>(ownerHandle);
} catch (const std::out_of_range &) {
if (*mutex != (ownerHandle | HandleWaitersBit))
return result::InvalidCurrentMemory;
if (__atomic_load_n(mutex, __ATOMIC_SEQ_CST) != (ownerHandle | HandleWaitersBit))
return failOnOutdated ? result::InvalidCurrentMemory : Result{};
return result::InvalidHandle;
}
@ -128,13 +128,10 @@ namespace skyline::kernel::type {
{
std::scoped_lock lock{owner->waiterMutex, state.thread->waiterMutex}; // We need to lock both mutexes at the same time as we mutate the owner and the current thread, the ordering of locks **must** match MutexUnlock to avoid deadlocks
u32 value{};
if (__atomic_compare_exchange_n(mutex, &value, tag, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
// We try to do a CAS to get ownership of the mutex in the case that it's unoccupied
return {};
u32 value{__atomic_load_n(mutex, __ATOMIC_SEQ_CST)};
if (value != (ownerHandle | HandleWaitersBit))
// We ensure that the mutex's value is the handle with the waiter bit set
return result::InvalidCurrentMemory;
return failOnOutdated ? result::InvalidCurrentMemory : Result{};
auto &waiters{owner->waiters};
isHighestPriority = waiters.insert(std::upper_bound(waiters.begin(), waiters.end(), state.thread->priority.load(), KThread::IsHigherPriority), state.thread) == waiters.begin();
@ -250,7 +247,7 @@ namespace skyline::kernel::type {
KHandle value{};
if (!__atomic_compare_exchange_n(mutex, &value, tag, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
while (MutexLock(mutex, value & ~HandleWaitersBit, tag) != Result{})
while (MutexLock(mutex, value & ~HandleWaitersBit, tag, true) != Result{})
if ((value = __atomic_or_fetch(mutex, HandleWaitersBit, __ATOMIC_SEQ_CST)) == HandleWaitersBit)
if (__atomic_compare_exchange_n(mutex, &value, tag, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
break;

3
app/src/main/cpp/skyline/kernel/types/KProcess.h
View File

@ -212,8 +212,9 @@ namespace skyline {
* @brief Locks the mutex at the specified address
* @param ownerHandle The psuedo-handle of the current mutex owner
* @param tag The handle of the thread which is requesting this lock
* @param failOnOutdated If true, the function will return InvalidCurrentMemory if the supplied ownerHandle is outdated
*/
Result MutexLock(u32 *mutex, KHandle ownerHandle, KHandle tag);
Result MutexLock(u32 *mutex, KHandle ownerHandle, KHandle tag, bool failOnOutdated = false);
/**
* @brief Unlocks the mutex at the specified address