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Kernel: Make entering and leaving critical sections atomic

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We also need to store m_in_critical in the Thread upon switching,
and we need to restore it. This solves a problem where threads
moving between different processors could end up with an unexpected
value.
This commit is contained in:
Tom 2021-01-23 22:24:10 -07:00 • committed by Andreas Kling
parent 33cdc1d2f1
commit f88a8b16d7
3 changed files with 25 additions and 13 deletions
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3
Kernel/Arch/i386/CPU.cpp
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@ -1291,6 +1291,7 @@ extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread)
write_cr3(to_tss.cr3);
to_thread->set_cpu(processor.id());
processor.restore_in_critical(to_thread->saved_critical());
asm volatile("fxrstor %0"
::"m"(to_thread->fpu_state()));
@ -1308,6 +1309,7 @@ void Processor::switch_context(Thread*& from_thread, Thread*& to_thread)
ASSERT(is_kernel_mode());
dbgln<CONTEXT_SWITCH_DEBUG>("switch_context --> switching out of: {} {}", VirtualAddress(from_thread), *from_thread);
from_thread->save_critical(m_in_critical);
// Switch to new thread context, passing from_thread and to_thread
// through to the new context using registers edx and eax
@ -1347,6 +1349,7 @@ void Processor::switch_context(Thread*& from_thread, Thread*& to_thread)
[to_eip] "c" (to_thread->tss().eip),
[from_thread] "d" (from_thread),
[to_thread] "a" (to_thread)
: "memory"
);
dbgln<CONTEXT_SWITCH_DEBUG>("switch_context <-- from {} {} to {} {}", VirtualAddress(from_thread), *from_thread, VirtualAddress(to_thread), *to_thread);