perf_counter/powerpc: Fix oops on cpus without perf_counter hardware support (f36a1a13) · Commits · 戴 / test

If we have the powerpc perf_counter backend compiled in, but the cpu we are running on is one where we don't support the PMU, we currently oops in hw_perf_group_sched_in if we try to use any counters, because ppmu is NULL in that case, and we unconditionally dereference ppmu. This fixes the problem by adding a check if ppmu is NULL at the beginning of hw_perf_group_sched_in, and also at the beginning of the other functions that get called from the perf_counter core, i.e. hw_perf_disable, hw_perf_enable, and hw_perf_counter_setup. Signed-off-by:

Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: benh@kernel.crashing.org Signed-off-by:

Ingo Molnar <mingo@elte.hu>

arch/powerpc/kernel/perf_counter.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -518,6 +518,8 @@ void hw_perf_disable(void)
		struct cpu_hw_counters *cpuhw;
		unsigned long flags;

		if (!ppmu)
		return;
		local_irq_save(flags);
		cpuhw = &__get_cpu_var(cpu_hw_counters);

		@@ -572,6 +574,8 @@ void hw_perf_enable(void)
		int n_lim;
		int idx;

		if (!ppmu)
		return;
		local_irq_save(flags);
		cpuhw = &__get_cpu_var(cpu_hw_counters);
		if (!cpuhw->disabled) {
		@@ -737,6 +741,8 @@ int hw_perf_group_sched_in(struct perf_counter *group_leader,
		long i, n, n0;
		struct perf_counter *sub;

		if (!ppmu)
		return 0;
		cpuhw = &__get_cpu_var(cpu_hw_counters);
		n0 = cpuhw->n_counters;
		n = collect_events(group_leader, ppmu->n_counter - n0,
		@@ -1281,6 +1287,8 @@ void hw_perf_counter_setup(int cpu)
		{
		struct cpu_hw_counters *cpuhw = &per_cpu(cpu_hw_counters, cpu);

		if (!ppmu)
		return;
		memset(cpuhw, 0, sizeof(*cpuhw));
		cpuhw->mmcr[0] = MMCR0_FC;
		}

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