On Mon, 31 Oct 2011 10:57:16 +0100 Michael Holzheu <holzheu at linux.vnet.ibm.com> wrote: > > Should this be done earlier in the function? As it stands we'll have > > multiple CPUs scribbling on buf[] at the same time and all trying to > > print the same thing at the same time, dumping their stacks, etc. > > Perhaps it would be better to single-thread all that stuff > > My fist patch took the spinlock at the beginning of panic(). But then > Eric asked, if it wouldn't be better to get both panic printk's and I > agreed. Hm, why? It will make a big mess. > > Also... this patch affects all CPU architectures, all configs, etc. > > So we're expecting that every architecture's smp_send_stop() is able to > > stop a CPU which is spinning in spin_lock(), possibly with local > > interrupts disabled. Will this work? > > At least on s390 it will work. If there are architectures that can't > stop disabled CPUs then this problem is already there without this > patch. > > Example: > > 1. 1st CPU gets lock X and panics > 2. 2nd CPU is disabled and gets lock X (irq-disabled) > 3. 1st CPU calls smp_send_stop() > -> 2nd CPU loops disabled and can't be stopped Well OK. Maybe some architectures do have this problem - who would notice? If that is the case, we just made the failure cases much more common. Could you check, please?
