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Suresh Siddha authored
commit 6d3321e8 upstream. MTRR rendezvous sequence using stop_one_cpu_nowait() can potentially happen in parallel with another system wide rendezvous using stop_machine(). This can lead to deadlock (The order in which works are queued can be different on different cpu's. Some cpu's will be running the first rendezvous handler and others will be running the second rendezvous handler. Each set waiting for the other set to join for the system wide rendezvous, leading to a deadlock). MTRR rendezvous sequence is not implemented using stop_machine() as this gets called both from the process context aswell as the cpu online paths (where the cpu has not come online and the interrupts are disabled etc). stop_machine() works with only online cpus. For now, take the stop_machine mutex in the MTRR rendezvous sequence that gets called from an online cpu (here we are in the process context and can potentially sleep while tak...
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