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Kernel: Prevent recursive calls into the scheduler

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Upon leaving a critical section (such as a SpinLock) we need to
check if we're already asynchronously invoking the Scheduler.
Otherwise we might end up triggering another context switch
as soon as leaving the scheduler lock.

Fixes #2883
This commit is contained in:
Tom 2020-08-01 14:37:40 -06:00 • committed by Andreas Kling
parent a19304c9d6
commit 728de56481
5 changed files with 136 additions and 21 deletions
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21
Kernel/Arch/i386/CPU.cpp
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@ -943,6 +943,7 @@ void Processor::early_initialize(u32 cpu)
m_message_queue = nullptr;
m_idle_thread = nullptr;
m_current_thread = nullptr;
m_scheduler_data = nullptr;
m_mm_data = nullptr;
m_info = nullptr;
@ -1188,9 +1189,9 @@ extern "C" void context_first_init(Thread* from_thread, Thread* to_thread, TrapF
// Since we got here and don't have Scheduler::context_switch in the
// call stack (because this is the first time we switched into this
// context), we need to unlock the scheduler lock manually. We're
// using the flags initially set up by init_context
g_scheduler_lock.unlock(trap->regs->eflags);
// context), we need to notify the scheduler so that it can release
// the scheduler lock.
Scheduler::leave_on_first_switch(trap->regs->eflags);
}
extern "C" void thread_context_first_enter(void);
@ -1335,6 +1336,7 @@ void Processor::assume_context(Thread& thread, u32 flags)
dbg() << "Assume context for thread " << VirtualAddress(&thread) << " " << thread;
#endif
ASSERT_INTERRUPTS_DISABLED();
Scheduler::prepare_after_exec();
// in_critical() should be 2 here. The critical section in Process::exec
// and then the scheduler lock
ASSERT(Processor::current().in_critical() == 2);
@ -1346,21 +1348,20 @@ extern "C" void pre_init_finished(void)
{
ASSERT(g_scheduler_lock.own_lock());
// The target flags will get restored upon leaving the trap
u32 prev_flags = cpu_flags();
g_scheduler_lock.unlock(prev_flags);
// We because init_finished() will wait on the other APs, we need
// Because init_finished() will wait on the other APs, we need
// to release the scheduler lock so that the other APs can also get
// to this point
// The target flags will get restored upon leaving the trap
u32 prev_flags = cpu_flags();
Scheduler::leave_on_first_switch(prev_flags);
}
extern "C" void post_init_finished(void)
{
// We need to re-acquire the scheduler lock before a context switch
// transfers control into the idle loop, which needs the lock held
ASSERT(!g_scheduler_lock.own_lock());
g_scheduler_lock.lock();
Scheduler::prepare_for_idle_loop();
}
void Processor::initialize_context_switching(Thread& initial_thread)