Messages in this thread | | | From | Sergey Senozhatsky <> | Date | Sat, 27 Apr 2019 02:16:40 +0900 | Subject | Re: [PATCH v4] panic: add an option to replay all the printk message in buffer |
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On (04/27/19 01:43), Sergey Senozhatsky wrote: [..] > > The console waiter logic is effective but it does not always > > work. The current console owner must be calling the console > > drivers. > > > > > Hmm, we might have a bit of a problem here, maybe. > > > > Hmm, the printk() might wait forever when NMI stopped > > the current console owner in the console driver code > > or with the logbuf_lock taken. > > I guess this is why we re-init logbuf lock from panic, > however, we don't do anything with the console_owner. > > > The console waiter logic might get solved by clearing > > the console_owner in console_flush_on_panic(). It can't > > be much worse, we already ignore console_lock() there, ...
Hmm, or maybe we are fine... console_waiter logic should work before we send out stop IPI/NMI from panic CPU. When we call flush_on_panic() console_unlock() clears console_owner, so panic_print_sys_info() should not deadlock on console_owner.
It's probably only problematic if we kill a console_owner CPU and then try to printk() (from smp_send_stop()) before we do flush_on_panic()->console_unlock().
-ss
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