• Yang Jihong's avatar
    perf/core: Fix reentry problem in perf_output_read_group() · 6b959ba2
    Yang Jihong authored
    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
    6b959ba2
core.c 323 KB