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a6dbf93a2a
Currently there is a bug where if you use oprofile on a pSeries machine, then use perf_counters, then use oprofile again, oprofile will not work correctly; it will lose the PMU configuration the next time the hypervisor does a partition context switch, and thereafter won't count anything. Maynard Johnson identified the sequence causing the problem: - oprofile setup calls ppc_enable_pmcs(), which calls pseries_lpar_enable_pmcs, which tells the hypervisor that we want to use the PMU, and sets the "PMU in use" flag in the lppaca. This flag tells the hypervisor whether it needs to save and restore the PMU config. - The perf_counter code sets and clears the "PMU in use" flag directly as it context-switches the PMU between tasks, and leaves it clear when it finishes. - oprofile setup, called for a new oprofile run, calls ppc_enable_pmcs, which does nothing because it has already been called. In particular it doesn't set the "PMU in use" flag. This fixes the problem by arranging for ppc_enable_pmcs to always set the "PMU in use" flag. It makes the perf_counter code call ppc_enable_pmcs also rather than calling the lower-level function directly, and removes the setting of the "PMU in use" flag from pseries_lpar_enable_pmcs, since that is now done in its caller. This also removes the declaration of pasemi_enable_pmcs because it isn't defined anywhere. Reported-by: Maynard Johnson <mpjohn@us.ibm.com> Signed-off-by: Paul Mackerras <paulus@samba.org> Cc: <stable@kernel.org) Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
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