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Kernel: Fix some problems with Thread::wait_on and Lock

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This changes the Thread::wait_on function to not enable interrupts
upon leaving, which caused some problems with page fault handlers
and in other situations. It may now be called from critical
sections, with interrupts enabled or disabled, and returns to the
same state.

This also requires some fixes to Lock. To aid debugging, a new
define LOCK_DEBUG is added that enables checking for Lock leaks
upon finalization of a Thread.
This commit is contained in:
Tom 2020-11-30 19:04:36 -07:00 • committed by Andreas Kling
parent 9e32d79e02
commit 78f1b5e359
10 changed files with 178 additions and 83 deletions
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58
Kernel/Thread.h
View file

@ -45,6 +45,8 @@
#include <LibC/fd_set.h>
#include <LibELF/AuxiliaryVector.h>
//#define LOCK_DEBUG
namespace Kernel {
enum class DispatchSignalResult {
@ -961,6 +963,44 @@ public:
RecursiveSpinLock& get_lock() const { return m_lock; }
#ifdef LOCK_DEBUG
void holding_lock(Lock& lock, bool holding, const char* file = nullptr, int line = 0)
{
m_holding_locks.fetch_add(holding ? 1 : -1, AK::MemoryOrder::memory_order_relaxed);
ScopedSpinLock list_lock(m_holding_locks_lock);
if (holding) {
bool have_existing = false;
for (size_t i = 0; i < m_holding_locks_list.size(); i++) {
auto& info = m_holding_locks_list[i];
if (info.lock == &lock) {
have_existing = true;
info.count++;
break;
}
}
if (!have_existing)
m_holding_locks_list.append({ &lock, file ? file : "unknown", line, 1 });
} else {
bool found = false;
for (size_t i = 0; i < m_holding_locks_list.size(); i++) {
auto& info = m_holding_locks_list[i];
if (info.lock == &lock) {
ASSERT(info.count > 0);
if (--info.count == 0)
m_holding_locks_list.remove(i);
found = true;
break;
}
}
ASSERT(found);
}
}
u32 lock_count() const
{
return m_holding_locks.load(AK::MemoryOrder::memory_order_relaxed);
}
#endif
private:
IntrusiveListNode m_runnable_list_node;
IntrusiveListNode m_wait_queue_node;
@ -1004,9 +1044,11 @@ private:
auto& blocker = static_cast<JoinBlocker&>(b);
// NOTE: m_lock is held already!
if (m_thread_did_exit)
if (m_thread_did_exit) {
blocker.unblock(exit_value(), true);
return m_thread_did_exit;
return false;
}
return true;
}
private:
@ -1050,6 +1092,18 @@ private:
const char* m_wait_reason { nullptr };
WaitQueue* m_queue { nullptr };
#ifdef LOCK_DEBUG
struct HoldingLockInfo {
Lock* lock;
const char* file;
int line;
unsigned count;
};
Atomic<u32> m_holding_locks { 0 };
SpinLock<u8> m_holding_locks_lock;
Vector<HoldingLockInfo> m_holding_locks_list;
#endif
JoinBlockCondition m_join_condition;
Atomic<bool> m_is_active { false };
bool m_is_joinable { true };