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ladybird/Kernel/Lock.cpp

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Meta: Add license header to source files As suggested by Joshua, this commit adds the 2-clause BSD license as a comment block to the top of every source file. For the first pass, I've just added myself for simplicity. I encourage everyone to add themselves as copyright holders of any file they've added or modified in some significant way. If I've added myself in error somewhere, feel free to replace it with the appropriate copyright holder instead. Going forward, all new source files should include a license header.
2020-01-18 11:38:21 +03:00
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
Kernel: Fix signal delivery When delivering urgent signals to the current thread we need to check if we should be unblocked, and if not we need to yield to another process. We also need to make sure that we suppress context switches during Process::exec() so that we don't clobber the registers that it sets up (eip mainly) by a context switch. To be able to do that we add the concept of a critical section, which are similar to Process::m_in_irq but different in that they can be requested at any time. Calls to Scheduler::yield and Scheduler::donate_to will return instantly without triggering a context switch, but the processor will then asynchronously trigger a context switch once the critical section is left.
2020-07-03 14:19:50 +03:00
#include <AK/TemporaryChange.h>
Kernel: Move all code into the Kernel namespace
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#include <Kernel/KSyms.h>
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
#include <Kernel/Lock.h>
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
#include <Kernel/Thread.h>
//#define LOCK_TRACE_DEBUG
//#define LOCK_RESTORE_DEBUG
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
Kernel: Move all code into the Kernel namespace
2020-02-16 03:27:42 +03:00
namespace Kernel {
Kernel: Fix some problems with Thread::wait_on and Lock 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.
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#ifdef LOCK_DEBUG
void Lock::lock(Mode mode)
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
{
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
lock("unknown", 0, mode);
Kernel: Introduce shared locking mode A Lock can now be held either in shared or exclusive mode. Multiple threads can hold the same lock in shared mode at one time, but if any thread holds the lock in exclusive mode, no other thread can hold it at the same time in either mode.
2020-04-18 12:21:00 +03:00
}
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
void Lock::lock(const char* file, int line, Mode mode)
#else
Kernel: Introduce shared locking mode A Lock can now be held either in shared or exclusive mode. Multiple threads can hold the same lock in shared mode at one time, but if any thread holds the lock in exclusive mode, no other thread can hold it at the same time in either mode.
2020-04-18 12:21:00 +03:00
void Lock::lock(Mode mode)
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
#endif
Kernel: Introduce shared locking mode A Lock can now be held either in shared or exclusive mode. Multiple threads can hold the same lock in shared mode at one time, but if any thread holds the lock in exclusive mode, no other thread can hold it at the same time in either mode.
2020-04-18 12:21:00 +03:00
{
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
// NOTE: This may be called from an interrupt handler (not an IRQ handler)
// and also from within critical sections!
ASSERT(!Processor::current().in_irq());
Kernel: Introduce shared locking mode A Lock can now be held either in shared or exclusive mode. Multiple threads can hold the same lock in shared mode at one time, but if any thread holds the lock in exclusive mode, no other thread can hold it at the same time in either mode.
2020-04-18 12:21:00 +03:00
ASSERT(mode != Mode::Unlocked);
Kernel: Turn Thread::current and Process::current into functions This allows us to query the current thread and process on a per processor basis
2020-06-29 00:34:31 +03:00
auto current_thread = Thread::current();
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ScopedCritical critical; // in case we're not in a critical section already
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
for (;;) {
Kernel: Minor Lock optimization
2020-10-29 05:03:15 +03:00
if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
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
2020-07-06 00:46:51 +03:00
do {
// FIXME: Do not add new readers if writers are queued.
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
auto current_mode = m_mode.load(AK::MemoryOrder::memory_order_relaxed);
switch (current_mode) {
case Mode::Unlocked: {
#ifdef LOCK_TRACE_DEBUG
dbg() << "Lock::lock @ " << this << ": acquire " << mode_to_string(mode) << ", currently unlocked";
#endif
m_mode.store(mode, AK::MemoryOrder::memory_order_relaxed);
ASSERT(!m_holder);
ASSERT(m_shared_holders.is_empty());
if (mode == Mode::Exclusive) {
m_holder = current_thread;
} else {
ASSERT(mode == Mode::Shared);
m_shared_holders.set(current_thread, 1);
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
}
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ASSERT(m_times_locked == 0);
m_times_locked++;
#ifdef LOCK_DEBUG
current_thread->holding_lock(*this, 1, file, line);
#endif
m_lock.store(false, AK::memory_order_release);
return;
}
case Mode::Exclusive: {
ASSERT(m_holder);
if (m_holder != current_thread)
break;
ASSERT(m_shared_holders.is_empty());
#ifdef LOCK_TRACE_DEBUG
if (mode == Mode::Exclusive)
dbg() << "Lock::lock @ " << this << ": acquire " << mode_to_string(mode) << ", currently exclusive, holding: " << m_times_locked;
else
dbg() << "Lock::lock @ " << this << ": acquire exclusive (requested " << mode_to_string(mode) << "), currently exclusive, holding " << m_times_locked;
#endif
ASSERT(mode == Mode::Exclusive || mode == Mode::Shared);
ASSERT(m_times_locked > 0);
m_times_locked++;
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
#ifdef LOCK_DEBUG
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
current_thread->holding_lock(*this, 1, file, line);
#endif
m_lock.store(false, AK::memory_order_release);
return;
}
case Mode::Shared: {
ASSERT(!m_holder);
if (mode != Mode::Shared)
break;
#ifdef LOCK_TRACE_DEBUG
dbg() << "Lock::lock @ " << this << ": acquire " << mode_to_string(mode) << ", currently shared, locks held: " << m_times_locked;
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
#endif
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ASSERT(m_times_locked > 0);
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
2020-07-06 00:46:51 +03:00
m_times_locked++;
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ASSERT(!m_shared_holders.is_empty());
auto it = m_shared_holders.find(current_thread);
if (it != m_shared_holders.end())
it->value++;
else
m_shared_holders.set(current_thread, 1);
#ifdef LOCK_DEBUG
current_thread->holding_lock(*this, 1, file, line);
#endif
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
2020-07-06 00:46:51 +03:00
m_lock.store(false, AK::memory_order_release);
return;
}
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
default:
ASSERT_NOT_REACHED();
}
Kernel: Fix some issues related to fixes and block conditions Fix some problems with join blocks where the joining thread block condition was added twice, which lead to a crash when trying to unblock that condition a second time. Deferred block condition evaluation by File objects were also not properly keeping the File object alive, which lead to some random crashes and corruption problems. Other problems were caused by the fact that the Queued state didn't handle signals/interruptions consistently. To solve these issues we remove this state entirely, along with Thread::wait_on and change the WaitQueue into a BlockCondition instead. Also, deliver signals even if there isn't going to be a context switch to another thread. Fixes #4336 and #4330
2020-12-08 07:29:41 +03:00
m_lock.store(false, AK::memory_order_release);
} while (m_queue.wait_on(nullptr, m_name) == Thread::BlockResult::NotBlocked);
Kernel: Lock needs to call Processor::wait_check while looping We need to process SMP messages while looping.
2020-10-27 01:48:51 +03:00
} else {
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
// I don't know *who* is using "m_lock", so just yield.
Scheduler::yield_from_critical();
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
}
}
}
void Lock::unlock()
{
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
// NOTE: This may be called from an interrupt handler (not an IRQ handler)
// and also from within critical sections!
ASSERT(!Processor::current().in_irq());
Kernel: Turn Thread::current and Process::current into functions This allows us to query the current thread and process on a per processor basis
2020-06-29 00:34:31 +03:00
auto current_thread = Thread::current();
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ScopedCritical critical; // in case we're not in a critical section already
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
for (;;) {
Kernel: Minor Lock optimization
2020-10-29 05:03:15 +03:00
if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
auto current_mode = m_mode.load(AK::MemoryOrder::memory_order_relaxed);
#ifdef LOCK_TRACE_DEBUG
if (current_mode == Mode::Shared)
dbg() << "Lock::unlock @ " << this << ": release " << mode_to_string(current_mode) << ", locks held: " << m_times_locked;
else
dbg() << "Lock::unlock @ " << this << ": release " << mode_to_string(current_mode) << ", holding: " << m_times_locked;
#endif
ASSERT(current_mode != Mode::Unlocked);
Kernel: Introduce shared locking mode A Lock can now be held either in shared or exclusive mode. Multiple threads can hold the same lock in shared mode at one time, but if any thread holds the lock in exclusive mode, no other thread can hold it at the same time in either mode.
2020-04-18 12:21:00 +03:00
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ASSERT(m_times_locked > 0);
m_times_locked--;
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
switch (current_mode) {
case Mode::Exclusive:
Kernel: Turn Thread::current and Process::current into functions This allows us to query the current thread and process on a per processor basis
2020-06-29 00:34:31 +03:00
ASSERT(m_holder == current_thread);
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ASSERT(m_shared_holders.is_empty());
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
if (m_times_locked == 0)
m_holder = nullptr;
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
break;
case Mode::Shared: {
ASSERT(!m_holder);
auto it = m_shared_holders.find(current_thread);
ASSERT(it != m_shared_holders.end());
if (it->value > 1) {
it->value--;
} else {
ASSERT(it->value > 0);
m_shared_holders.remove(it);
}
break;
}
default:
ASSERT_NOT_REACHED();
}
if (m_times_locked == 0) {
ASSERT(current_mode == Mode::Exclusive ? !m_holder : m_shared_holders.is_empty());
m_mode.store(Mode::Unlocked, AK::MemoryOrder::memory_order_relaxed);
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
}
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
#ifdef LOCK_DEBUG
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
current_thread->holding_lock(*this, -1);
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
#endif
Kernel: Introduce shared locking mode A Lock can now be held either in shared or exclusive mode. Multiple threads can hold the same lock in shared mode at one time, but if any thread holds the lock in exclusive mode, no other thread can hold it at the same time in either mode.
2020-04-18 12:21:00 +03:00
Kernel: Fix some issues related to fixes and block conditions Fix some problems with join blocks where the joining thread block condition was added twice, which lead to a crash when trying to unblock that condition a second time. Deferred block condition evaluation by File objects were also not properly keeping the File object alive, which lead to some random crashes and corruption problems. Other problems were caused by the fact that the Queued state didn't handle signals/interruptions consistently. To solve these issues we remove this state entirely, along with Thread::wait_on and change the WaitQueue into a BlockCondition instead. Also, deliver signals even if there isn't going to be a context switch to another thread. Fixes #4336 and #4330
2020-12-08 07:29:41 +03:00
m_lock.store(false, AK::memory_order_release);
m_queue.wake_one();
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
return;
}
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
2019-12-01 13:57:20 +03:00
// I don't know *who* is using "m_lock", so just yield.
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
Scheduler::yield_from_critical();
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
}
}
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
auto Lock::force_unlock_if_locked(u32& lock_count_to_restore) -> Mode
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
{
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
// NOTE: This may be called from an interrupt handler (not an IRQ handler)
// and also from within critical sections!
ASSERT(!Processor::current().in_irq());
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
auto current_thread = Thread::current();
ScopedCritical critical; // in case we're not in a critical section already
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
for (;;) {
if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
Mode previous_mode;
auto current_mode = m_mode.load(AK::MemoryOrder::memory_order_relaxed);
switch (current_mode) {
case Mode::Exclusive: {
if (m_holder != current_thread) {
m_lock.store(false, AK::MemoryOrder::memory_order_release);
lock_count_to_restore = 0;
return Mode::Unlocked;
}
#ifdef LOCK_RESTORE_DEBUG
dbg() << "Lock::force_unlock_if_locked @ " << this << ": unlocking exclusive with lock count: " << m_times_locked;
#endif
m_holder = nullptr;
ASSERT(m_times_locked > 0);
lock_count_to_restore = m_times_locked;
m_times_locked = 0;
m_mode.store(Mode::Unlocked, AK::MemoryOrder::memory_order_relaxed);
m_lock.store(false, AK::memory_order_release);
#ifdef LOCK_DEBUG
m_holder->holding_lock(*this, -(int)lock_count_to_restore);
#endif
previous_mode = Mode::Exclusive;
break;
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
}
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
case Mode::Shared: {
ASSERT(!m_holder);
auto it = m_shared_holders.find(current_thread);
if (it == m_shared_holders.end()) {
m_lock.store(false, AK::MemoryOrder::memory_order_release);
lock_count_to_restore = 0;
return Mode::Unlocked;
}
#ifdef LOCK_RESTORE_DEBUG
dbg() << "Lock::force_unlock_if_locked @ " << this << ": unlocking exclusive with lock count: " << it->value << ", total locks: " << m_times_locked;
#endif
ASSERT(it->value > 0);
lock_count_to_restore = it->value;
ASSERT(lock_count_to_restore > 0);
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
#ifdef LOCK_DEBUG
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
m_holder->holding_lock(*this, -(int)lock_count_to_restore);
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
#endif
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
m_shared_holders.remove(it);
ASSERT(m_times_locked >= lock_count_to_restore);
m_times_locked -= lock_count_to_restore;
if (m_times_locked == 0)
m_mode.store(Mode::Unlocked, AK::MemoryOrder::memory_order_relaxed);
m_lock.store(false, AK::memory_order_release);
previous_mode = Mode::Shared;
break;
}
case Mode::Unlocked: {
m_lock.store(false, AK::memory_order_relaxed);
lock_count_to_restore = 0;
previous_mode = Mode::Unlocked;
break;
}
default:
ASSERT_NOT_REACHED();
}
Kernel: Fix some issues related to fixes and block conditions Fix some problems with join blocks where the joining thread block condition was added twice, which lead to a crash when trying to unblock that condition a second time. Deferred block condition evaluation by File objects were also not properly keeping the File object alive, which lead to some random crashes and corruption problems. Other problems were caused by the fact that the Queued state didn't handle signals/interruptions consistently. To solve these issues we remove this state entirely, along with Thread::wait_on and change the WaitQueue into a BlockCondition instead. Also, deliver signals even if there isn't going to be a context switch to another thread. Fixes #4336 and #4330
2020-12-08 07:29:41 +03:00
m_queue.wake_one();
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
return previous_mode;
}
// I don't know *who* is using "m_lock", so just yield.
Scheduler::yield_from_critical();
}
}
#ifdef LOCK_DEBUG
void Lock::restore_lock(Mode mode, u32 lock_count)
{
return restore_lock("unknown", 0, mode, lock_count);
}
void Lock::restore_lock(const char* file, int line, Mode mode, u32 lock_count)
#else
void Lock::restore_lock(Mode mode, u32 lock_count)
#endif
{
ASSERT(mode != Mode::Unlocked);
ASSERT(lock_count > 0);
ASSERT(!Processor::current().in_irq());
auto current_thread = Thread::current();
ScopedCritical critical; // in case we're not in a critical section already
for (;;) {
if (m_lock.exchange(true, AK::memory_order_acq_rel) == false) {
switch (mode) {
case Mode::Exclusive: {
auto expected_mode = Mode::Unlocked;
if (!m_mode.compare_exchange_strong(expected_mode, Mode::Exclusive, AK::MemoryOrder::memory_order_relaxed))
break;
#ifdef LOCK_RESTORE_DEBUG
dbg() << "Lock::restore_lock @ " << this << ": restoring " << mode_to_string(mode) << " with lock count " << lock_count << ", was unlocked";
#endif
ASSERT(m_times_locked == 0);
m_times_locked = lock_count;
ASSERT(!m_holder);
ASSERT(m_shared_holders.is_empty());
m_holder = current_thread;
m_lock.store(false, AK::memory_order_release);
#ifdef LOCK_DEBUG
m_holder->holding_lock(*this, (int)lock_count, file, line);
#endif
return;
}
case Mode::Shared: {
auto expected_mode = Mode::Unlocked;
if (!m_mode.compare_exchange_strong(expected_mode, Mode::Shared, AK::MemoryOrder::memory_order_relaxed) && expected_mode != Mode::Shared)
break;
#ifdef LOCK_RESTORE_DEBUG
dbg() << "Lock::restore_lock @ " << this << ": restoring " << mode_to_string(mode) << " with lock count " << lock_count << ", was " << mode_to_string(expected_mode);
#endif
ASSERT(expected_mode == Mode::Shared || m_times_locked == 0);
m_times_locked += lock_count;
ASSERT(!m_holder);
ASSERT((expected_mode == Mode::Unlocked) == m_shared_holders.is_empty());
auto set_result = m_shared_holders.set(current_thread, lock_count);
// There may be other shared lock holders already, but we should not have an entry yet
ASSERT(set_result == AK::HashSetResult::InsertedNewEntry);
m_lock.store(false, AK::memory_order_release);
#ifdef LOCK_DEBUG
m_holder->holding_lock(*this, (int)lock_count, file, line);
#endif
return;
}
default:
ASSERT_NOT_REACHED();
}
m_lock.store(false, AK::memory_order_relaxed);
Kernel: Fix some problems with Thread::wait_on and Lock 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.
2020-12-01 05:04:36 +03:00
}
// I don't know *who* is using "m_lock", so just yield.
Scheduler::yield_from_critical();
}
Kernel: Oops, forgot to add Lock.cpp.
2019-07-29 13:00:14 +03:00
}
Kernel: Move all code into the Kernel namespace
2020-02-16 03:27:42 +03:00
Kernel: Allow process with multiple threads to call exec and exit This allows a process wich has more than 1 thread to call exec, even from a thread. This kills all the other threads, but it won't wait for them to finish, just makes sure that they are not in a running/runable state. In the case where a thread does exec, the new program PID will be the thread TID, to keep the PID == TID in the new process. This introduces a new function inside the Process class, kill_threads_except_self which is called on exit() too (exit with multiple threads wasn't properly working either). Inside the Lock class, there is the need for a new function, clear_waiters, which removes all the waiters from the Process::big_lock. This is needed since after a exit/exec, there should be no other threads waiting for this lock, the threads should be simply killed. Only queued threads should wait for this lock at this point, since blocked threads are handled in set_should_die.
2020-02-18 15:28:28 +03:00
void Lock::clear_waiters()
{
Kernel: Fix Lock race causing infinite spinning between two threads We need to account for how many shared lock instances the current thread owns, so that we can properly release such references when yielding execution. We also need to release the process lock when donating.
2020-12-15 02:36:22 +03:00
ASSERT(m_mode.load(AK::MemoryOrder::memory_order_relaxed) != Mode::Shared);
Kernel: Fix some issues related to fixes and block conditions Fix some problems with join blocks where the joining thread block condition was added twice, which lead to a crash when trying to unblock that condition a second time. Deferred block condition evaluation by File objects were also not properly keeping the File object alive, which lead to some random crashes and corruption problems. Other problems were caused by the fact that the Queued state didn't handle signals/interruptions consistently. To solve these issues we remove this state entirely, along with Thread::wait_on and change the WaitQueue into a BlockCondition instead. Also, deliver signals even if there isn't going to be a context switch to another thread. Fixes #4336 and #4330
2020-12-08 07:29:41 +03:00
m_queue.wake_all();
Kernel: Allow process with multiple threads to call exec and exit This allows a process wich has more than 1 thread to call exec, even from a thread. This kills all the other threads, but it won't wait for them to finish, just makes sure that they are not in a running/runable state. In the case where a thread does exec, the new program PID will be the thread TID, to keep the PID == TID in the new process. This introduces a new function inside the Process class, kill_threads_except_self which is called on exit() too (exit with multiple threads wasn't properly working either). Inside the Lock class, there is the need for a new function, clear_waiters, which removes all the waiters from the Process::big_lock. This is needed since after a exit/exec, there should be no other threads waiting for this lock, the threads should be simply killed. Only queued threads should wait for this lock at this point, since blocked threads are handled in set_should_die.
2020-02-18 15:28:28 +03:00
}
Kernel: Move all code into the Kernel namespace
2020-02-16 03:27:42 +03:00
}
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