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Kernel: Fix some flaws that caused crashes or hangs during boot

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We need to halt the BSP briefly until all APs are ready for the
first context switch, but we can't hold the same spinlock by all
of them while doing so. So, while the APs are waiting on each other
they need to release the scheduler lock, and then once signaled
re-acquire it. Should solve some timing dependent hangs or crashes,
most easily observed using qemu with kvm disabled.
This commit is contained in:
Tom 2020-07-08 15:20:36 -06:00 • committed by Andreas Kling
parent 5d9ea2c787
commit b02d33bd63
4 changed files with 146 additions and 120 deletions
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27
Kernel/Arch/i386/CPU.cpp
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@ -990,8 +990,6 @@ void Processor::initialize(u32 cpu)
if (cpu >= s_processors->size())
s_processors->resize(cpu + 1);
(*s_processors)[cpu] = this;
klog() << "CPU[" << cpu << "]: initialized Processor at " << VirtualAddress(FlatPtr(this));
}
}
@ -1344,6 +1342,27 @@ void Processor::assume_context(Thread& thread, u32 flags)
ASSERT_NOT_REACHED();
}
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
// to release the scheduler lock so that the other APs can also get
// to this point
}
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();
}
void Processor::initialize_context_switching(Thread& initial_thread)
{
ASSERT(initial_thread.process().is_ring0());
@ -1368,9 +1387,11 @@ void Processor::initialize_context_switching(Thread& initial_thread)
"addl $20, %%ebx \n" // calculate pointer to TrapFrame
"pushl %%ebx \n"
"cld \n"
"pushl %[cpu] \n"
"pushl %[cpu] \n" // push argument for init_finished before register is clobbered
"call pre_init_finished \n"
"call init_finished \n"
"addl $4, %%esp \n"
"call post_init_finished \n"
"call enter_trap_no_irq \n"
"addl $4, %%esp \n"
"lret \n"