Hi Peter,

On Sep 3, 2021, at 1:27 AM, Peter Zijlstra [off-list ref] wrote:

On Thu, Sep 02, 2021 at 09:57:04AM -0700, Song Liu wrote:

quoted

+static int
+intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int cnt)
+{
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+
+	intel_pmu_disable_all();
+	intel_pmu_lbr_read();
+	cnt = min_t(unsigned int, cnt, x86_pmu.lbr_nr);
+
+	memcpy(entries, cpuc->lbr_entries, sizeof(struct perf_branch_entry) * cnt);
+	intel_pmu_enable_all(0);
+	return cnt;
+}

Given this disables the PMI from 'random' contexts, should we not add
IRQ disabling around this to avoid really bad behaviour?

Do you mean we should add (instead of not add) IRQ disable?

Thanks,
Song