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Kernel: Fix deadlock when unicasting/broadcasting SMP message

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When two processors send each others a SMP message at the same time
they need to process messages while waiting for delivery of the
message they just sent, or they will deadlock.
This commit is contained in:
Tom 2020-11-01 10:14:27 -07:00 • committed by Andreas Kling
parent 3ee7c21fae
commit dc9ddf8104
1 changed files with 8 additions and 10 deletions
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18
Kernel/Arch/i386/CPU.cpp
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@ -1884,11 +1884,10 @@ void Processor::smp_broadcast_message(ProcessorMessage& msg, bool async)
while (atomic_load(&msg.refs, AK::MemoryOrder::memory_order_consume) != 0) {
// TODO: pause for a bit?
// We need to check here if another processor may have requested
// us to halt before this message could be delivered. Otherwise
// we're just spinning the CPU because msg.refs will never drop to 0.
if (cur_proc.m_halt_requested.load(AK::MemoryOrder::memory_order_relaxed))
halt_this();
// We need to process any messages that may have been sent to
// us while we're waiting. This also checks if another processor
// may have requested us to halt.
cur_proc.smp_process_pending_messages();
}
smp_cleanup_message(msg);
@ -1934,11 +1933,10 @@ void Processor::smp_unicast_message(u32 cpu, ProcessorMessage& msg, bool async)
while (atomic_load(&msg.refs, AK::MemoryOrder::memory_order_consume) != 0) {
// TODO: pause for a bit?
// We need to check here if another processor may have requested
// us to halt before this message could be delivered. Otherwise
// we're just spinning the CPU because msg.refs will never drop to 0.
if (cur_proc.m_halt_requested.load(AK::MemoryOrder::memory_order_relaxed))
halt_this();
// We need to process any messages that may have been sent to
// us while we're waiting. This also checks if another processor
// may have requested us to halt.
cur_proc.smp_process_pending_messages();
}
smp_cleanup_message(msg);