On 12.09.12 13:20:43, Peter Zijlstra wrote:
> On Wed, 2012-09-12 at 13:01 +0200, Robert Richter wrote:
> > + if (notsup)
> > + pr_warn("perf: unsupported attribute flags: %016llx\n",
> > notsup);
>
> This is a dmesg DoS..
This could be avoided by introducing a cpuinfo like sysfs file for
each pmu:
/sys/bus/event_source/devices/*/flags
Then, userspace should know how to correctly setup the syscall. All
supported attributes would be known to perf and messages would thrown
only if something goes unexpected wrong.
I suggested this already here:
https://lkml.org/lkml/2012/8/3/214
https://lkml.org/lkml/2012/9/6/472
> I'm also not sure dmesg is the right way.. could we not somehow change
> the attrs to provide better diagnostic?
I found this discussion without a solution for the problem:
http://lwn.net/Articles/374794/
Other options could be pr_debug() or trace_printk()'s for debugging
purposes. Or an error report in sysfs:
cat /sys/bus/event_source/devices/*/log
But the pmu type needs to be known for this.
-Robert
--
Advanced Micro Devices, Inc.
Operating System Research Center
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