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Kernel: Verify interrupts are disabled when interacting with Mutexes

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This should help prevent deadlocks where a thread blocks on a Mutex
while interrupts are disabled, and makes it impossible for the holder of
the Mutex to make forward progress because it cannot be scheduled in.

Hide it behind a new debug macro LOCK_IN_CRITICAL_DEBUG for now, because
Ext2FS takes a series of Mutexes from the page fault handler, which
executes with interrupts disabled.
This commit is contained in:
Andrew Kaster 2021-08-22 22:06:44 -06:00 committed by Andreas Kling
parent 4f2520674c
commit 72de228695
Notes: sideshowbarker 2024-07-18 05:08:34 +09:00 
Author: https://github.com/ADKaster
Commit: https://github.com/SerenityOS/serenity/commit/72de228695f
Pull-request: https://github.com/SerenityOS/serenity/pull/9580
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/bgianfo
3 changed files with 11 additions and 0 deletions
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4
Kernel/Debug.h.in
View file

@ -166,6 +166,10 @@
#cmakedefine01 LOCK_DEBUG
#endif
#ifndef LOCK_IN_CRITICAL_DEBUG
#cmakedefine01 LOCK_IN_CRITICAL_DEBUG
#endif
#ifndef LOCK_RESTORE_DEBUG
#cmakedefine01 LOCK_RESTORE_DEBUG
#endif

6
Kernel/Locking/Mutex.cpp
View file

@ -18,6 +18,8 @@ void Mutex::lock(Mode mode, [[maybe_unused]] LockLocation const& location)
// NOTE: This may be called from an interrupt handler (not an IRQ handler)
// and also from within critical sections!
VERIFY(!Processor::current_in_irq());
if constexpr (LOCK_IN_CRITICAL_DEBUG)
VERIFY_INTERRUPTS_ENABLED();
VERIFY(mode != Mode::Unlocked);
auto current_thread = Thread::current();
@ -143,6 +145,8 @@ void Mutex::unlock()
{
// NOTE: This may be called from an interrupt handler (not an IRQ handler)
// and also from within critical sections!
if constexpr (LOCK_IN_CRITICAL_DEBUG)
VERIFY_INTERRUPTS_ENABLED();
VERIFY(!Processor::current_in_irq());
auto current_thread = Thread::current();
SpinlockLocker lock(m_lock);
@ -198,6 +202,8 @@ void Mutex::unlock()
void Mutex::block(Thread& current_thread, Mode mode, SpinlockLocker<Spinlock<u8>>& lock, u32 requested_locks)
{
if constexpr (LOCK_IN_CRITICAL_DEBUG)
VERIFY_INTERRUPTS_ENABLED();
auto& blocked_thread_list = thread_list_for_mode(mode);
VERIFY(!blocked_thread_list.contains(current_thread));
blocked_thread_list.append(current_thread);

1
Meta/CMake/all_the_debug_macros.cmake
View file

@ -101,6 +101,7 @@ set(LEXER_DEBUG ON)
set(LINE_EDITOR_DEBUG ON)
set(LOCAL_SOCKET_DEBUG ON)
set(LOCK_DEBUG ON)
set(LOCK_IN_CRITICAL_DEBUG ON)
set(LOCK_RESTORE_DEBUG ON)
set(LOCK_TRACE_DEBUG ON)
set(LOOKUPSERVER_DEBUG ON)