From: Yang Jihong yangjihong1@huawei.com
commit 6b959ba22d34ca793ffdb15b5715457c78e38b1a upstream.
perf_output_read_group may respond to IPI request of other cores and invoke __perf_install_in_context function. As a result, hwc configuration is modified. causing inconsistency and unexpected consequences.
Interrupts are not disabled when perf_output_read_group reads PMU counter. In this case, IPI request may be received from other cores. As a result, PMU configuration is modified and an error occurs when reading PMU counter:
CPU0 CPU1 __se_sys_perf_event_open perf_install_in_context perf_output_read_group smp_call_function_single for_each_sibling_event(sub, leader) { generic_exec_single if ((sub != event) && remote_function (sub->state == PERF_EVENT_STATE_ACTIVE)) | <enter IPI handler: __perf_install_in_context> <----RAISE IPI-----+ __perf_install_in_context ctx_resched event_sched_out armpmu_del ... hwc->idx = -1; // event->hwc.idx is set to -1 ... <exit IPI> sub->pmu->read(sub); armpmu_read armv8pmu_read_counter armv8pmu_read_hw_counter int idx = event->hw.idx; // idx = -1 u64 val = armv8pmu_read_evcntr(idx); u32 counter = ARMV8_IDX_TO_COUNTER(idx); // invalid counter = 30 read_pmevcntrn(counter) // undefined instruction
Signed-off-by: Yang Jihong yangjihong1@huawei.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20220902082918.179248-1-yangjihong1@huawei.com Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@igalia.com ---
This race may also lead to observed behavior like RCU stalls, hang tasks, OOM. Likely due to list corruption or a similar root cause.
--- kernel/events/core.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 4e5a73c7db12..e79cd0fd1d2b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7119,9 +7119,16 @@ static void perf_output_read_group(struct perf_output_handle *handle, { struct perf_event *leader = event->group_leader, *sub; u64 read_format = event->attr.read_format; + unsigned long flags; u64 values[6]; int n = 0;
+ /* + * Disabling interrupts avoids all counter scheduling + * (context switches, timer based rotation and IPIs). + */ + local_irq_save(flags); + values[n++] = 1 + leader->nr_siblings;
if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) @@ -7157,6 +7164,8 @@ static void perf_output_read_group(struct perf_output_handle *handle,
__output_copy(handle, values, n * sizeof(u64)); } + + local_irq_restore(flags); }
#define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\