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Commit 37a65df6 authored by Yang Jihong's avatar Yang Jihong Committed by Greg Kroah-Hartman
Browse files

perf/core: Fix reentry problem in perf_output_read_group() 



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: default avatarYang Jihong <yangjihong1@huawei.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220902082918.179248-1-yangjihong1@huawei.com


Signed-off-by: default avatarThadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 86102171

kernel/events/core.c

+9 −0
Original line number Diff line number Diff line
@@ -6372,9 +6372,16 @@ 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)
@@ -6410,6 +6417,8 @@ 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|\