Description LeoLiu-oc 2024-06-25 19:07:29 UTC

A CPU executing vprintk_emit might be interrupted by #PF exception,
this may leads to logbuf_lock deadlock:

CPU x:                            CPU x:
----                              ----
vprintk_emit()
  logbuf_lock_irqsave()
    printk_safe_enter_irqsave()
A:  raw_spin_lock(&logbuf_lock)
  vprintk_store()                 #PF
                                  do_page_fault
                                    ...
                                    oops_end
                                      bust_spinlocks(0)
                                        console_unlock()
                                          ...
                                          printk_safe_enter_irqsave()
B:                                        raw_spin_lock(&logbuf_lock)

logbuf_lock is taken at A and the deadlock happends at B.

Pass 1 to bust_spinlocks() in the oops_end() to avoid this deadlock.