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Kernel/SMP: Make entering/leaving critical sections multi-processor safe

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By making these functions static we close a window where we could get
preempted after calling Processor::current() and move to another
processor.

Co-authored-by: Tom <tomut@yahoo.com>
This commit is contained in:
Andreas Kling 2021-08-10 01:16:08 +02:00
parent 369e3da6a2
commit 9babb92a4b
11 changed files with 82 additions and 53 deletions
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14
Kernel/Thread.cpp
View file

@ -214,7 +214,7 @@ void Thread::block(Kernel::Mutex& lock, ScopedSpinLock<SpinLock<u8>>& lock_lock,
for (;;) {
// Yield to the scheduler, and wait for us to resume unblocked.
VERIFY(!g_scheduler_lock.own_lock());
VERIFY(Processor::current().in_critical());
VERIFY(Processor::in_critical());
if (&lock != &big_lock && big_lock.own_lock()) {
// We're locking another lock and already hold the big lock...
// We need to release the big lock
@ -222,7 +222,7 @@ void Thread::block(Kernel::Mutex& lock, ScopedSpinLock<SpinLock<u8>>& lock_lock,
} else {
yield_assuming_not_holding_big_lock();
}
VERIFY(Processor::current().in_critical());
VERIFY(Processor::in_critical());
ScopedSpinLock block_lock2(m_block_lock);
if (should_be_stopped() || state() == Stopped) {
@ -389,7 +389,7 @@ void Thread::die_if_needed()
// Now leave the critical section so that we can also trigger the
// actual context switch
u32 prev_flags;
Processor::current().clear_critical(prev_flags, false);
Processor::clear_critical(prev_flags, false);
dbgln("die_if_needed returned from clear_critical!!! in irq: {}", Processor::current().in_irq());
// We should never get here, but the scoped scheduler lock
// will be released by Scheduler::context_switch again
@ -421,9 +421,9 @@ void Thread::yield_assuming_not_holding_big_lock()
InterruptDisabler disable;
Scheduler::yield(); // flag a switch
u32 prev_flags;
u32 prev_crit = Processor::current().clear_critical(prev_flags, true);
u32 prev_crit = Processor::clear_critical(prev_flags, true);
// NOTE: We may be on a different CPU now!
Processor::current().restore_critical(prev_crit, prev_flags);
Processor::restore_critical(prev_crit, prev_flags);
}
void Thread::yield_and_release_relock_big_lock()
@ -452,12 +452,12 @@ void Thread::relock_process(LockMode previous_locked, u32 lock_count_to_restore)
// We have to do it this way because we intentionally
// leave the critical section here to be able to switch contexts.
u32 prev_flags;
u32 prev_crit = Processor::current().clear_critical(prev_flags, true);
u32 prev_crit = Processor::clear_critical(prev_flags, true);
// CONTEXT SWITCH HAPPENS HERE!
// NOTE: We may be on a different CPU now!
Processor::current().restore_critical(prev_crit, prev_flags);
Processor::restore_critical(prev_crit, prev_flags);
if (previous_locked != LockMode::Unlocked) {
// We've unblocked, relock the process if needed and carry on.