x86, perf_counter, bts: Do not allow kernel BTS tracing for now (1653192f) · Commits · e / devices / android_kernel_fairphone_FP4

Kernel BTS tracing generates too much data too fast for us to handle, causing the kernel to hang. Fail for BTS requests for kernel code. Signed-off-by:

Markus Metzger <markus.t.metzger@intel.com> Acked-by:

Peter Zijlstra <a.p.zjilstra@chello.nl> LKML-Reference: <20090902140616.901253000@intel.com> [ This is really a workaround - but we want BTS tracing in .32 so make sure we dont regress. The lockup should be fixed ASAP. ] Signed-off-by:

Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_counter.c

+9 −2

Original line number	Original line	Diff line number	Diff line
	@@ -984,9 +984,16 @@ static int __hw_perf_counter_init(struct perf_counter *counter)
	* Branch tracing:		* Branch tracing:
	*/		*/
	if ((attr->config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS) &&		if ((attr->config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS) &&
	(hwc->sample_period == 1) && !bts_available())		(hwc->sample_period == 1)) {
			/* BTS is not supported by this architecture. */
			if (!bts_available())
	return -EOPNOTSUPP;		return -EOPNOTSUPP;

			/* BTS is currently only allowed for user-mode. */
			if (hwc->config & ARCH_PERFMON_EVENTSEL_OS)
			return -EOPNOTSUPP;
			}

	hwc->config \|= config;		hwc->config \|= config;

	return 0;		return 0;