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047a3772fe
Don found that P4 PMU reads CCCR register instead of counter itself (in attempt to catch unflagged event) this makes P4 NMI handler to consume all NMIs it observes. So the other NMI users such as kgdb simply have no chance to get NMI on their hands. Side note: at moment there is no way to run nmi-watchdog together with perf tool. This is because both 'perf top' and nmi-watchdog use same event. So while nmi-watchdog reserves one event/counter for own needs there is no room for perf tool left (there is a way to disable nmi-watchdog on boot of course). Ming has tested this patch with the following results | 1. watchdog disabled | | kgdb tests on boot OK | perf works OK | | 2. watchdog enabled, without patch perf-x86-p4-nmi-4 | | kgdb tests on boot hang | | 3. watchdog enabled, without patch perf-x86-p4-nmi-4 and do not run kgdb | tests on boot | | "perf top" partialy works | cpu-cycles no | instructions yes | cache-references no | cache-misses no | branch-instructions no | branch-misses yes | bus-cycles no | | 4. watchdog enabled, with patch perf-x86-p4-nmi-4 applied | | kgdb tests on boot OK | perf does not work, NMI "Dazed and confused" messages show up | Which means we still have problems with p4 box due to 'unknown' nmi happens but at least it should fix kgdb test cases. Reported-by: Jason Wessel <jason.wessel@windriver.com> Reported-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Acked-by: Don Zickus <dzickus@redhat.com> Acked-by: Lin Ming <ming.m.lin@intel.com> Cc: Stephane Eranian <eranian@google.com> Cc: Peter Zijlstra <peterz@infradead.org> LKML-Reference: <4D275E7E.3040903@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
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| .. | ||
| boot | ||
| configs | ||
| crypto | ||
| ia32 | ||
| include/asm | ||
| kernel | ||
| kvm | ||
| lguest | ||
| lib | ||
| math-emu | ||
| mm | ||
| oprofile | ||
| pci | ||
| platform | ||
| power | ||
| tools | ||
| vdso | ||
| video | ||
| xen | ||
| .gitignore | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.cpu | ||
| Kconfig.debug | ||
| Makefile | ||
| Makefile_32.cpu | ||