On Thu, 24 April 2014 12:58:21 -0700, Greg Kroah-Hartman wrote: > > @@ -868,11 +870,20 @@ static size_t print_time(u64 ts, char *buf) > > > > rem_nsec = do_div(ts, 1000000000); > > > > +#ifdef CONFIG_PRINTK_CPU > > + if (!buf) > > + return snprintf(NULL, 0, "[%5lu.000000,%02x] ", > > %02x for a cpu? What happens on machines with 8k cpus?
You should get something like: Apr 23 10:34:03 [ 228.950926,1a] Call Trace: Apr 23 10:34:03 [ 228.950926,201] Call Trace: Apr 23 10:34:03 [ 228.950928,1a] [<ffffffff815e0f29>] schedule+0x29/0x70 ... That said, I don't have access to hardware with >256 cpus and haven't actually tested this. > And is this really an issue? Debugging by using printk is fun, but not > really something that people need to add a cpu number to. Why not just > use a tracepoint in your code to get the needed information instead? Yes, this is an issue. There have been several instances in my life when I would have had to guess which function belonged to which backtrace without this patch. Good guesses take a long time, bad guesses are nearly useless and giving up means you cannot debug the issue. I don't have a good example at hand, but here is something from a quick grep for illustration. Feb 22 19:04:46 [ 11.642470,2e] Call Trace: Feb 22 19:04:46 [ 11.642472,16] Call Trace: Feb 22 19:04:46 [ 11.642476,29] [<ffffffff81115bf8>] pcpu_alloc+0x988/0xa20 Feb 22 19:04:46 [ 11.642481,01] [<ffffffff810992ad>] ? find_symbol+0x3d/0xb0 Feb 22 19:04:46 [ 11.642489,05] [<ffffffff81115bf8>] pcpu_alloc+0x988/0xa20 Feb 22 19:04:46 [ 11.642493,12] [<ffffffff81115bf8>] pcpu_alloc+0x988/0xa20 Feb 22 19:04:46 [ 11.642498,08] [<ffffffff81115bf8>] pcpu_alloc+0x988/0xa20 Feb 22 19:04:46 [ 11.642504,21] [<ffffffff810992ad>] ? find_symbol+0x3d/0xb0 And are you seriously suggesting I use a tracepoint for kernel panics? ;) Jörn -- There's nothing better for promoting creativity in a medium than making an audience feel "Hmm I could do better than that!" -- Douglas Adams in a slashdot interview -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
