mirror of
https://github.com/RGBCube/serenity
synced 2025-05-28 22:35:06 +00:00
Kernel: Enhance WaitQueue to remember pending wakes
If WaitQueue::wake_all, WaitQueue::wake_one, or WaitQueue::wake_n is called but nobody is currently waiting, we should remember that fact and prevent someone from waiting after such a request. This solves a race condition where the Finalizer thread is notified to finalize a thread, but it is not (yet) waiting on this queue. Fixes #2693
This commit is contained in:
parent
2a82a25fec
commit
9725bda63e
5 changed files with 93 additions and 27 deletions
|
@ -54,6 +54,7 @@ void Lock::lock(Mode mode)
|
|||
for (;;) {
|
||||
bool expected = false;
|
||||
if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
|
||||
do {
|
||||
// FIXME: Do not add new readers if writers are queued.
|
||||
bool modes_dont_conflict = !modes_conflict(m_mode, mode);
|
||||
bool already_hold_exclusive_lock = m_mode == Mode::Exclusive && m_holder == current_thread;
|
||||
|
@ -66,8 +67,7 @@ void Lock::lock(Mode mode)
|
|||
m_lock.store(false, AK::memory_order_release);
|
||||
return;
|
||||
}
|
||||
timeval* timeout = nullptr;
|
||||
current_thread->wait_on(m_queue, m_name, timeout, &m_lock, m_holder);
|
||||
} while (current_thread->wait_on(m_queue, m_name, nullptr, &m_lock, m_holder) == Thread::BlockResult::NotBlocked);
|
||||
} else if (Processor::current().in_critical()) {
|
||||
// If we're in a critical section and trying to lock, no context
|
||||
// switch will happen, so yield.
|
||||
|
|
|
@ -872,12 +872,18 @@ Thread::BlockResult Thread::wait_on(WaitQueue& queue, const char* reason, timeva
|
|||
// we need to wait until the scheduler lock is released again
|
||||
{
|
||||
ScopedSpinLock sched_lock(g_scheduler_lock);
|
||||
if (!queue.enqueue(*Thread::current())) {
|
||||
// The WaitQueue was already requested to wake someone when
|
||||
// nobody was waiting. So return right away as we shouldn't
|
||||
// be waiting
|
||||
return BlockResult::NotBlocked;
|
||||
}
|
||||
|
||||
did_unlock = unlock_process_if_locked();
|
||||
if (lock)
|
||||
*lock = false;
|
||||
set_state(State::Queued);
|
||||
m_wait_reason = reason;
|
||||
queue.enqueue(*Thread::current());
|
||||
|
||||
|
||||
if (timeout) {
|
||||
|
|
|
@ -301,6 +301,7 @@ public:
|
|||
|
||||
enum class BlockResult {
|
||||
WokeNormally,
|
||||
NotBlocked,
|
||||
InterruptedBySignal,
|
||||
InterruptedByDeath,
|
||||
InterruptedByTimeout,
|
||||
|
|
|
@ -27,8 +27,11 @@
|
|||
#include <Kernel/Thread.h>
|
||||
#include <Kernel/WaitQueue.h>
|
||||
|
||||
//#define WAITQUEUE_DEBUG
|
||||
|
||||
namespace Kernel {
|
||||
|
||||
|
||||
WaitQueue::WaitQueue()
|
||||
{
|
||||
}
|
||||
|
@ -37,10 +40,20 @@ WaitQueue::~WaitQueue()
|
|||
{
|
||||
}
|
||||
|
||||
void WaitQueue::enqueue(Thread& thread)
|
||||
bool WaitQueue::enqueue(Thread& thread)
|
||||
{
|
||||
ScopedSpinLock queue_lock(m_lock);
|
||||
if (m_wake_requested) {
|
||||
// wake_* was called when no threads were in the queue
|
||||
// we shouldn't wait at all
|
||||
m_wake_requested = false;
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": enqueue: wake_all pending";
|
||||
#endif
|
||||
return false;
|
||||
}
|
||||
m_threads.append(thread);
|
||||
return true;
|
||||
}
|
||||
|
||||
void WaitQueue::wake_one(Atomic<bool>* lock)
|
||||
|
@ -48,42 +61,87 @@ void WaitQueue::wake_one(Atomic<bool>* lock)
|
|||
ScopedSpinLock queue_lock(m_lock);
|
||||
if (lock)
|
||||
*lock = false;
|
||||
if (m_threads.is_empty())
|
||||
if (m_threads.is_empty()) {
|
||||
// Save the fact that a wake was requested
|
||||
m_wake_requested = true;
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_one: nobody to wake, mark as pending";
|
||||
#endif
|
||||
return;
|
||||
if (auto* thread = m_threads.take_first())
|
||||
}
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_one:";
|
||||
#endif
|
||||
auto* thread = m_threads.take_first();
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_one: wake thread " << *thread;
|
||||
#endif
|
||||
thread->wake_from_queue();
|
||||
m_wake_requested = false;
|
||||
Scheduler::yield();
|
||||
}
|
||||
|
||||
void WaitQueue::wake_n(i32 wake_count)
|
||||
void WaitQueue::wake_n(u32 wake_count)
|
||||
{
|
||||
ScopedSpinLock queue_lock(m_lock);
|
||||
if (m_threads.is_empty())
|
||||
if (m_threads.is_empty()) {
|
||||
// Save the fact that a wake was requested
|
||||
m_wake_requested = true;
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_n: nobody to wake, mark as pending";
|
||||
#endif
|
||||
return;
|
||||
}
|
||||
|
||||
for (i32 i = 0; i < wake_count; ++i) {
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_n: " << wake_count;
|
||||
#endif
|
||||
for (u32 i = 0; i < wake_count; ++i) {
|
||||
Thread* thread = m_threads.take_first();
|
||||
if (!thread)
|
||||
break;
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_n: wake thread " << *thread;
|
||||
#endif
|
||||
thread->wake_from_queue();
|
||||
}
|
||||
m_wake_requested = false;
|
||||
Scheduler::yield();
|
||||
}
|
||||
|
||||
void WaitQueue::wake_all()
|
||||
{
|
||||
ScopedSpinLock queue_lock(m_lock);
|
||||
if (m_threads.is_empty())
|
||||
if (m_threads.is_empty()) {
|
||||
// Save the fact that a wake was requested
|
||||
m_wake_requested = true;
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_all: nobody to wake, mark as pending";
|
||||
#endif
|
||||
return;
|
||||
while (!m_threads.is_empty())
|
||||
m_threads.take_first()->wake_from_queue();
|
||||
}
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_all: ";
|
||||
#endif
|
||||
while (!m_threads.is_empty()) {
|
||||
Thread* thread = m_threads.take_first();
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": wake_all: wake thread " << *thread;
|
||||
#endif
|
||||
thread->wake_from_queue();
|
||||
}
|
||||
m_wake_requested = false;
|
||||
Scheduler::yield();
|
||||
}
|
||||
|
||||
void WaitQueue::clear()
|
||||
{
|
||||
ScopedSpinLock queue_lock(m_lock);
|
||||
#ifdef WAITQUEUE_DEBUG
|
||||
dbg() << "WaitQueue " << VirtualAddress(this) << ": clear";
|
||||
#endif
|
||||
m_threads.clear();
|
||||
m_wake_requested = false;
|
||||
}
|
||||
|
||||
}
|
||||
|
|
|
@ -38,9 +38,9 @@ public:
|
|||
WaitQueue();
|
||||
~WaitQueue();
|
||||
|
||||
void enqueue(Thread&);
|
||||
bool enqueue(Thread&);
|
||||
void wake_one(Atomic<bool>* lock = nullptr);
|
||||
void wake_n(i32 wake_count);
|
||||
void wake_n(u32 wake_count);
|
||||
void wake_all();
|
||||
void clear();
|
||||
|
||||
|
@ -48,6 +48,7 @@ private:
|
|||
typedef IntrusiveList<Thread, &Thread::m_wait_queue_node> ThreadList;
|
||||
ThreadList m_threads;
|
||||
SpinLock<u32> m_lock;
|
||||
bool m_wake_requested { false };
|
||||
};
|
||||
|
||||
}
|
||||
|
|
Loading…
Add table
Add a link
Reference in a new issue